Scooter tuning, how to properly tune a scooter

Scooter tuning, how to properly tune a scooter Scooter tuning using the example of Honda Dio AF-18 Remove 50 - put 72. Replacing the piston on a scooter CVT tuning. Adjusting the weight of the variator weights using available materials

How do you do your own scooter tuning? Why does a scooter need tuning at all? To answer, we need to figure out why we need a scooter at all?

It’s one thing when a scooter makes it possible to forget about traffic jams and heat, and the fuel consumption is minimal. Everything is clear here with fifty dollars - the time comes when more dynamics and maximum speed are required/wanted. By intelligently approaching increasing the performance of a scooter, we will get the desired result. It’s another matter if we have a scooter as a means to stand out from the crowd, to amaze everyone with amazing acceleration and an impressive bass note from the exhaust. Here the direction of tuning is completely different. And in general, it often makes sense to simply change the scooter to a more powerful one rather than tuning a fifty-kopeck piece.

Speaking of low-budget boosting, click here, Cheap tuning of the Honda Dio scooter, and read the article about wallet-friendly tuning.

Well, later in this article we’ll talk about how and what to do for tuning, and for serious tuning of a scooter, with your own hands or someone else’s, and most importantly, wisely. And to such things as His Majesty, sir, “big scooter tuning”, i.e. Scooter tuning, which is noticeably superior to budget ones both in scale and in cost, must be approached extremely meticulously and carefully. This means that you can’t do it without the skill and instinct of a mechanic.

However, let’s start small here too.

So, after running in and removing the speed limiters (chokers), we have several ways to increase the maximum speed a little and get a much more powerful engine with almost the same resource. Don’t forget about the technical condition of the remaining parts and components of your scooter, otherwise the simplest and most inexpensive do-it-yourself tuning can result in a rather complicated and expensive scooter repair! already, perhaps, by someone else’s, more skillful hands . So:

Change the scooter muffler to a tuning resonance pipe that fits your CPG (pipes such as Laser X, LeoVince ZX, Technigas Next - R in various versions may be suitable) or to a “torque” exhaust (Polini No Smoke, LeoVince SP3/Turing, Techigas Silent Pro). Also rebuild the transmission part in accordance with the characteristics of the installed tuning pipe. This will allow you to raise the maximum speed of the scooter by another 10-15 km/h (for resonant exhaust) and will give an increase in dynamics.
Get a carburetor with an optimal diffuser diameter. For 50-70cc, the most convenient to configure and install is a carburetor with a diffuser diameter of 17.5 mm, the most commonly used carburetor. There is an opinion that DellOrto tuning carburetors are of the highest quality, although by and large, the manufacturer does not really matter.
CVT - replace with a sports one. In tuning CVTs, the process of adjusting to new parameters of a scooter’s engine is more accurate and of better quality - due to more advanced kinematics of moving weights. Tuning CVTs produced by Polini after 2005 are equipped with a rod lubrication system, which increases the efficiency of the entire scooter transmission. And due to the smoother and easier movement of the variator cheek along the guide sleeve, it improves the acceleration response of the scooter.
The main way to increase the power of a scooter is, of course, to install a Sport class of increased volume. Generally speaking, this is the most radical and most effective method of increasing the performance of a scooter. Thus, you not only have an increased cylinder volume, but also a more competent and thoughtful system of the cylinder purging process (for a two-stroke engine) - that is, even more power. The main difference between two-stroke piston tuning kits from different manufacturers is precisely the different placement of windows. A cylinder head with an optimized combustion chamber shape - usually complete with a tuning CPG. Keep in mind that when installing piston engines with a larger piston diameter (volume), it is extremely important and necessary that the crankshaft and bearings be in perfect technical condition, otherwise large loads will simply destroy them very quickly.

In principle, the average person can stop at this level of scooter tuning, because the next stage is do-it-yourself scooter tuning, which allows you to develop up to 12-17 hp. on the shaft - this is the “design” of an engine on a tuning piston class Mid-Race and Race. And this is a qualitatively new level of tuning, and as mentioned above, for many it is easier to simply purchase a more powerful stock scooter than to tune it. So, tuning Mid-Race and Race class scooters.

Such engine tuning requires the installation of a reinforced crankshaft - with suitable bearings and a corresponding reinforced connecting rod. Only such tuning parts of a scooter engine are able to withstand increased shock loads and realize new power. Otherwise, you can forget about stable and trouble-free operation of the engine.

The crankshaft speed of an engine of this class begins to set the rhythm. 10,000 rpm requires adequate reliability of the components, which stock (i.e. standard factory) parts, such as main bearings, are not able to provide. In addition, the new thirsty engine needs appropriate power - the diameter of the carburetor diffuser should not be less than 17.5 mm for a racing piston engine. Also, the carburetor setting for this tuning engine must provide a good mixture at high speeds, otherwise overheating and further “sticking”, and in severe cases, the wedge of the cylinder cannot be avoided. It would be nice to install a 19 mm carburetor paired with a tuning sports air filter.

In fact, all the following steps for further tuning the scooter with your own hands will repeat the previous stage of boosting, only with the difference that it is necessary to use higher quality and more productive components of tuning kits. That is, instead of a regular sports CVT, it is strongly recommended to use Polini Evo or Malossi OverRange transmission tuning kits.

Tuning in this class allows you to develop dizzying dynamics and a hurricane maximum speed of over 100 km/h. In general, for normal use of a scooter in the city without too much investment in fuel and lubricants and consumables, this is the maximum possible tuning of the scooter. But such tuning allows you to enjoy real amazing dynamics and speed (this especially traumatizes the already unstable psyche of drivers of pseudo-sports cars, who for some reason underestimate the possibilities of tuning a scooter with their own hands and are perplexed when a “crazy stool” gives them heat from a traffic light as if they were standing , and often leaves them no chance for revenge ).

So we have reached the pinnacle of boosting - tuning a Hi-End . These are uncompromising solutions that allow you to increase the liter power of a scooter engine to a figure exceeding 300 (three hundred!) horsepower per liter of volume! And this is without the use of all sorts of turbines and other sophisticated solutions like nitrous oxide or special fuel!

There are not so many companies involved in such developments. The main players in this field are Malossi, Polini, Kunda, 2Fast, Fabrizi, MetraKit. These are elite components and a triumph of high technology.

With this tuning, engine speed comes close to 20,000 rpm! There can be no savings here, the work is only for the result - the task of such a motor is to work out two 15-minute sessions and several hours of training, after which it is sent for inspection and subsequent replacement of worn-out components. Even crankshaft bearings most often come in special series and can only be purchased from the tuning studios themselves (Malossi and Polini have their own special bearings that were developed and manufactured exclusively for them).

Installation of the crankshaft, CPG and other components requires a very serious modification of the engine crankcase and chassis of the scooter; the use of rotary ignition is mandatory (which allows you to spin the engine to insane speeds without losing spark power), which implies the absence of all electrics not related to the scooter’s ignition system . The ratio in the gearbox is left to the taste and wishes of the owner.

The best examples of fine-tuning scooters using components of this class allow achieving time at a completely “adult” distance of 402 meters within 12-14 seconds, and not everyone, even seriously “charged” cars, are capable of such “feats”.

In urban use, the service life before replacing the ring is expressed as a figure from 1500 to 4000 km, so if it is possible to “feed” such an engine with first-class 98 gasoline (not the kind that is poured at 99% of gas stations, but real) and very expensive oil, then you can and sometimes ride such a monster to scooter-moto parties and amaze the imagination of those passing by with shining sides and polished engine covers, and after the cool motorcycle racers stop nervously giggling from the chirping of a newly started engine, accompanied by a fair amount of smoke from the exhaust pipe (you will have to pour oil “by eye” and, preferably, and, naturally, in not the most optimal proportions), open the trigger fully and take out a couple of “purebred” (ZZR 400 =) sports bikes. So let someone after this say that scooters are consumption for children “under 16”...

This, in general terms, is all about tuning scooters with your own hands. But each scooter is unique, each scooterist has his own requirements, so each scooter should be prepared based on many conditions - budget, requirements and the feasibility of one or another modification, because it is not for nothing that there are so many “transitional” classes on the scooter tuning market that do not fit into the standard ones the framework of one or another forcing class.

The following is a list of tuning kits provided by various scooter parts manufacturers.

Scooter tuning - CPG tuning

The variety of tuning cylinders offered is quite large, including standard 50cc and more powerful 70cc. Standard 50 cc tuning cylinders provide an increase in scooter power due to the improved design of the cylinder itself, and 70 cc cylinders also due to a 40% increase in volume. In this case, the scooter becomes much faster than stock.

But comparing cylinders of the same displacement, it is clear that they all produce different results. This is due to the fact that different cylinders are designed for different operating speed ranges of the engine. Hence the differing effective power. Tuning cylinders for scooters are usually classified into Sport, Midrace (Racing) and Hi-End. The lifespan of the scooter's Sport cylinders is approximately equal to the lifespan of the standard ones, since these cylinders are adapted to the same engine speed.

In addition, these Sport class cylinders are usually no more expensive than similar standard parts

Different racing tuning piston class Racing 70cc differ from each other. These are such manufacturers of CPGs as Top Due Plus, Polini Corsa, Malossi MHR Replica, Hebo Manston Replica. For example, cylinders from Hebo and Malossi have high quality, wear resistance and power. These are aluminum CPGs with a very durable chrome-nickasil coating. Cast iron racing scooter cylinders from Top Performances and Polini are generally just as good. An aluminum cylinder undoubtedly has the best heat transfer. But if it is damaged, you will have to change both the piston with rings and the cylinder (this can happen from, for example, a lack of oil in the mixture, or when it is depleted). However, cast iron piston engines in such emergency situations can only get by by replacing the piston, and the surface of the cylinder should be polished. Racing cylinders have much higher compression and compression ratios (up to 14:1), as well as engine speed. All this requires mandatory strengthening of the crankshaft; it should be replaced with a tuned one from a racing kit.

Cylinder-piston group.

Finally, the most effective improvement for any engine is replacing the CPG. But not just a replacement, but the installation of a new, larger piston. Fortunately, there are now many ready-made kits on the market; you don’t have to sharpen or adjust anything, as with Soviet equipment. Moreover, there is even a lot to choose from. For example, for various models with a volume of 50 cubic meters, they offer kits to increase to 63, 72, 82 and even 90+ cubic cm. In some cases, this is an almost double increase in power.

The situation is similar with larger engines, for example, for 125 cubic meters, sets of 150 or 170 cubic meters are sold. Some, in the process of tuning a scooter, manage to increase 150 cubic meters with their own hands to 225 cubic meters. Choosing the right part is not the most difficult thing, the most difficult thing is installing it. After all, this process involves almost complete disassembly of the engine. You will be faced with the need to have several special removable keys in your arsenal; you can ask them from friends or borrow them for the evening at auto repair shops. We strongly recommend studying the technical component in order to properly disassemble, replace the necessary elements and assemble the motor.

Alas, for some, increased power does not promise anything other than breakdowns or inadequate performance. This is because by significantly increasing power, you inevitably entail work on all other nodes. Let's imagine that we installed a new 92 cc CPG on an old 50 cc engine. The first thing to check is the condition of the connecting rod, crankshaft and bearings. Otherwise, they will fly first, followed by our new system of both cylinder and piston.

Great, we added new bearings to the CPG, an elbow with a connecting rod, now we can be sure of reliability. But the engine does not go faster, and we decide to purchase a new carburetor. Now the mixture is too rich, and we understand that the exhaust needs to be changed. After such modifications, the engine sounds loud, accelerates perfectly, but the maximum speed is slightly higher than before and the variator sounds strange. After installing a high-speed CVT, for example from the Italian manufacturer Polini, the engine will be able to fully realize its new power. The last stage is an inspection of the brake system; you don’t want to find out at a speed of 60 km/h that the brakes are now comparable to bicycle ones.

As a result, after replacing almost all the components, we got a very fast “flea” that can surprise your friends and experts in this technology. Over time, you can make changes to the chassis system, replace shock absorbers, and install more attractive wheels. Often, the modernization process does not stop there, and after tuning a scooter 50, 150 with your own hands, impressive improvements in appearance are made. The moped is repainted, panels are changed, new devices, lighting, and so on appear.

Scooter tuning - crankshaft tuning

Once you have decided on the cylinder, the next question is whether to change the crankshaft. The answer to this largely depends on the class of cylinder that you have chosen for yourself. When using Midrace and Hi-End class cylinders, replacing the crankshaft is mandatory! Installing cylinders of the indicated classes in combination with a standard crankshaft is a gross violation and an indicator of the unprofessionalism of the people involved in installing parts on the scooter.

In all the variety of tuning crankshafts, it is necessary to distinguish two groups. The first one is simply reinforced

. They replicate the corresponding standard crankshafts in all respects, but have greater strength (and therefore a longer service life), as well as improved heat removal from the piston pin. Reinforced crankshafts are great for use with Sport class piston when there is a need to replace the standard one.

The second group is racing crankshafts (the abbreviation HPC is often used - high primary compression). Such crankshafts significantly affect engine performance, as they provide an increase in the compression ratio in the engine crankcase. This significantly improves the efficiency of cylinder scavenging at high speeds, providing an increase in power. At the “lower” ranges, the efficiency of purging, on the contrary, suffers, but for forced engines this is not significant. Racing crankshafts are indispensable when it comes to tuning based on Racing class piston engines.

When replacing the crankshaft, it is recommended to replace the main bearings with oil seals.

Professional boosting of 50cc scooters

All 50cc scooters supplied to Europe are limited in speed to 50 km/h. This is achieved in the following ways:

Electronic - maximum engine speed is limited

Mechanical - limited increase in gear ratio in the variator

Using limiters on the exhaust and inlet - limiting the filling of the cylinder with the mixture

Of course, many manufacturers combine these methods to obtain better results. Before you start tuning your scooter in order to increase its speed and throttle response, you should completely remove all the limiters installed by the manufacturer.

The greatest trouble in this sense is caused by electronic limiters - they are usually hard-wired into the ignition system switch. Among other things, almost all modern commutators have a built-in engine speed limiter - to prevent excessive rotation of the engine when, for example, the variator belt breaks, the only difference is that for a conventional commutator this limiter is set to a level of 7000-7500 rpm, and for speed limit, the manufacturer changes the setting to ~6000 rpm. In any case, both types of limiter settings are unacceptable to force the scooter, so you should purchase and install a special sports switch. They come in two types - without a rev limiter at all and with an adjustable limiter (usually switchable in steps to levels 7000-9500-11500-13000). The second type is preferable - as it protects the motor from damage when the speed exceeds the permissible zone.

In fact, there are only four main areas of boosting a scooter (I will list them in the logical sequence of modifications made):

Exhaust system

Cylinder volume

Changing the transmission gear ratio

Improving the carburetor and intake So, let's do the tuning in order:

1. Exhaust system

There are several main types of exhaust systems (what is usually called a muffler) available on the market: Standard (factory) mufflers from “semi-sport” scooter models (such as the Suzuki Sepia ZZ or Honda Dio ZX). These mufflers provide some increase in engine power with virtually no increase in optimal engine speed, mainly due to improved filling of the cylinder with the mixture and sharpening of the torque characteristics of the engine.

Tuning mufflers that provide an increase of about 20% in power due to a slight increase in the optimal engine speed, which necessitates restructuring the variator to ensure high throttle response (using lighter weights and, sometimes, a stiffer return spring). A striking example of such a muffler is the LeoVinci SP3.

Tuning mufflers of the sports class, providing an increase of about 50% of power due to a significant increase in engine speed, and requiring, in order to ensure high throttle response, not only a restructuring of the variator (using lighter weights and, often, a stiffer return spring), but also a restructuring of the centrifugal clutch (using stiffer return springs or completely replacing the clutch with a tuning one). A striking example of such a muffler is the LeoVinci ZX (and indeed the entire series of LeoVinci sports mufflers).

Of course, an increase in engine speed causes an increase in the maximum speed of the scooter (without changing the gear ratio of the rear gearbox) in proportion to the increase in speed. In general, standard scooter engines have a maximum speed of about 7000 rpm. The SP3 muffler increases them by 750-1000 rpm, and the ZX muffler - by 1750-2000 rpm, as a result, if initially the Yamaha Jog ran 70 km/h, then with the SP3 muffler it will run at least 80 km/h, and with ZX - 90 km/h. At the same time, the acceleration dynamics of the scooter will significantly improve.

2. Cylinder volume

Many manufacturers of tuning kits - Malossi, Polini, DR, Eurocilindro - produce piston group kits of increased volume (cylinder, piston with rings and pin, often a new cylinder head) for 50cc scooters. The most popular sizes are 70cc and 85cc (about 68 and 84 cc), the most popular design is a steel cylinder with an aluminum head, although more advanced aluminum cylinders with Nicosil coating are sometimes available. Such kits are installed on a standard crankshaft with a connecting rod and provide a huge increase in power at nominal (or slightly above nominal) speed. Nicosil-coated cylinders can withstand higher rpm and provide more power and torque than steel cylinders, but their durability is highly dependent on the quality of their workmanship, and they are much more sensitive to overheating than steel ones.

Also available on the market are racing-type piston tuning kits (for example, Polini Kit Corsa), which provide very high engine power, but are practically unsuitable for use in normal road conditions due to capriciousness and the requirement for very frequent maintenance to maintain performance. In particular, standard piston rings, replaced on conventional cylinders after 10,000 km, on the Polini Kit Corsa 70cc cylinder become unusable after 2000-3000 km.

3. Rear gearbox

A feature of 50cc scooters with automatic transmission is that even with a significant increase in the power of their engine (especially due to an increase in its volume), their maximum speed increases slightly, since the device is overly strangled by the rear gearbox (its gear ratio is too high for the increased engine power) .

Therefore, the next step after increasing the cylinder volume should be the purchase of a tuning kit for the rear gearbox (the so-called Gear Kit). Typical Gear Kits reduce the rear gear ratio by 50-70%, increasing the maximum speed of your scooter by about the same amount (at the cost of slightly reducing throttle response) - of course, if you have enough engine power. With an 85cc road-class cylinder and Gear-Kit, a regular Yamaha Jog reaches speeds of 110-120 km/h, with a racing cylinder even higher.

4. Carburetor improvement

English and French tuning firms believe that even a 12mm carburetor is not the limiting element for a 50cc engine, much less the typical 14mm Teikei, Mikuni or Dell'Orto carburetor installed on almost all modern 50cc scooter models. However, after installing a cylinder with a volume of 70cc (and especially 80-85cc), increasing the size of the carburetor diffuser begins to significantly add power to the engine. Most 70cc and 85cc road cylinders will be fine with a 17mm or 18mm Dell'Orto carburetor, but a 70-85cc race cylinder may need a 22mm carburetor.

Typically, replacing a carburetor is accompanied by replacing the installation elements surrounding it - all sorts of holders, pipes, etc., and is also often accompanied by the installation of a new air filter with increased capacity. Actually, the sets of tuning carburetors Malossi and Polini consist of a carburetor with a set of similar installation parts.

5. Transmission: an unattainable compromise

I will not present now the details of the design of the variator and clutch, limiting myself to stating the main principle of operation of the automatic transmission of a scooter: the variator strives to keep the engine speed constant - at the optimal level for maximum engine power, changing the gear ratio in proportion to the load. Streamlining, in turn, allows the engine to reach rated speed before moving off, and disengages the engine from the wheel when the gas is suddenly released - to ensure coasting (at a moderate speed). }}

Since engine tuning changes its characteristics in terms of optimal speed, this requires reconfiguring the variator and clutch.

Even worse, the variator, designed to transmit the power of a standard 50cc engine, when working with the increased torque of powerful tuning engines (70cc and especially 85cc), begins to work with belt slippage, which reduces the speed and leads to very rapid wear of the variator belt and discs. The variator is especially prone to slipping when starting from a stop and at low speed - in these modes, the belt runs along a small radius of the drive disk (that is, its contact patch with the disks is minimal) and at the same time is the weakest tensioned (due to the maximum convergence of the drive disks). The only way to counter this is to increase the tension of the variator return spring (or, which is better, install a special, harder tuning variator).

The clutch also needs to be reconfigured - especially if you used tuning that sharpens the characteristics of the engine, because for a dynamic start from a standstill, it is necessary that by the time the clutch pads engage, the engine has managed to gain speed close to optimal power. In addition, the clutch is also not always able to withstand the increased torque of the engine without slipping - therefore, on cars with engines of 70cc and above, you should think about replacing it with a tuning three-pad Polini or Malossi.

Ready-made recipes

Professional tuning is a delicate thing, it does not come down to the stupid installation of tuning kits, this is only the first phase of work, and the second, which accounts for 80-90% of the labor intensity, is the adjustment of this entire economy to optimal parameters and just normal joint work, and the more radical tuning - the more difficult the second part of the work, the more highly qualified it requires.

However, I still dare to give some simple recipes:

For beginners, I would recommend buying a set of LeoVinci tuning muffler (SP3 is cheaper and less noisy, RS and ZX are more expensive and much louder), its kit includes weights for rebuilding the variator and springs for rebuilding the clutch - install all this, rebuild the standard carburetor and with that limit yourself. Of course, take the set exactly for your scooter model - otherwise the setup will not be optimal. In the future, you can buy a racing commutator (preferably a model with an adjustable rev limit). If you have done this tuning on cheap scooter models (such as Yamaha Jog, Honda Dio, Suzuki Sepia), then you should start tuning the suspension and frame, since they have characteristics unsuitable for increased speeds.

For qualified highway enthusiasts, you should purchase a LeoVinci muffler (TOURING if you don't want to scare everyone around with the roar, and RS or ZX if you do), a standard 70cc cylinder (from Polini or Malossi) and a Gear Kit. The maximum speed will be high, the throttle response will be acceptable, the service life of the engine and rings will not decrease significantly. In the future you can buy a 17-18mm carburetor. Tuning suspensions and frames becomes essential, unless, of course, you are the owner of a Yamaha Aerox or BW's Bump.

For road maniacs, you should purchase a LeoVinci ZX muffler, a standard 70-85cc cylinder (from Polini or Malossi), a 22mm carburetor, a tuning CVT and a Gear Kit from Polini. If you don’t replace the crankshaft with a tuning one, the standard one will fall apart very quickly. Tuning the frame and suspension is required.

For athletes, you should purchase a LeoVinci ZX muffler, a 70-85cc sports cylinder (KitCorsa Polini or MHR Malossi), a 22mm carburetor, a tuning variator, a clutch and Gear Kit from Polini, a tuning crankshaft from Polini or Malossi, as well as a special racing switch. Deep tuning of the frame and suspension is required.

Of course, these are just the basic ideas. All this requires precise adjustment to each other in order to obtain truly high performance and an acceptable service life of the entire unit and individual parts.

Scooter tuning - muffler tuning (exhaust system)

A good exhaust system can easily help you add horsepower to your scooter. The operating features of a two-stroke engine are such that a well-chosen exhaust system can increase power by up to 20%, which is a very significant amount. Moreover, modern scooters, forced to meet the most stringent environmental requirements, are equipped as standard with exhaust systems that have a detrimental effect on performance.

Exhaust systems, like cylinders, are divided into different classes, so you need to choose a system based on the piston system that will be used on the scooter. Sport class exhaust systems are quite versatile. Many of them show excellent results with both standard 50cc cylinders and 70cc Sport class cylinders. But not all, so you should be careful when choosing. Pipes from certain manufacturers have proven themselves to be extremely short-lived and fragile, so you should not buy the first pipe you come across.

Chrome-plated exhaust systems deserve special attention: they retain their appearance much better and are also protected from corrosion, which is very important in Russian operating conditions!

Cleaning the cylinder from carbon deposits and filing down the cylinder window

Most production scooters offer enormous scope for tuning. And motor tuning is practically a national pastime: it’s rare that a scooter owner doesn’t want to show everyone who’s king on the road. And doing this is not at all as difficult as it seems - just work a little with a roller cutter.

After their first season of riding a scooter, many people have a desire to start upgrading the hardware. Some, having disassembled the engine and seeing that everything is in excellent condition, stop there. But if you look closely (especially in the case of a Chinese scooter), it is quite possible to detect casting defects in the exhaust channel and carbon deposits stuck to the rough surfaces (as happened in our case, see photo). In this case, it is simply necessary to polish and clean the cylinder (carbon deposits create resistance to the flow of exhaust gases, and therefore reduce power).

First you need to wash the cylinder of external dirt from the cylinder and free the exhaust window from carbon deposits . Please note: the round mark left by the gasket on the cylinder at its junction with the muffler shows the limit of the window expansion from the outside - otherwise (if you overdo it with the cutter) when you first start the engine you will hear the exhaust gases “siphoning” through the gap between the cylinder and the exhaust pipe.

Now we could proceed to the main thing - expanding the window. We grind off the cavities (see photo below) on the channel walls with a rolling cutter and cut off large casting defects - the window has expanded by 2 mm and added 1 mm “in height”. The outer part can be processed without much effort - it has little effect on the technical characteristics of the motor. But all irregularities inside the exhaust tract must be carefully “cut down”. The next step is to round the edges of the window with a file. You should be as careful as possible with them, otherwise the sharp edges will subsequently “chop” the piston rings.

Scooter tuning - carburetor tuning

You can get more complete output from a larger-volume piston by appropriately improving the operation of the power system. First of all, we are talking about the carburetor. Scooters come standard with carburetors from a variety of manufacturers, but they all have a common feature by which they can be classified - the size of the diffuser.

On standard 50cc engines there are carburetors with diffusers from 12 to 17.5mm. Tuning carburetors are also diverse: there are cases of installing even 28mm carburetors on 70cc tuning engines, but all this is already in the realm of experimentation. Carburetors with a diffuser diameter of more than 17.5 mm (19, 21, 24, etc.) are impractical to operate and require regular attention and reconfiguration. Of course, all this is not important if you are going to make a street rocket out of a scooter, sacrificing convenience and reliability.

A standard and proven recommendation for 70cc cylinders is to install a 17.5 carburetor, if one is not included in the standard equipment (for example, on the latest Piaggio HiPer2 engines).

The principle of operation of ignition in a 4-stroke scooter engine

Modern scooters are equipped with contactless systems. They are considered the most reliable and easy to use, do not require complex connections, and provide a constant good spark on time. However, the setting is still important; even the presence of a spark does not always allow the fuel mixture to ignite, since its power also plays a role.

The main reasons for the operation of the ignition system are quite simple: its task is to create a spark to detonate the fuel mixture. If this does not happen, you need to carefully examine each node and find out why the spark disappeared.

In order to check whether there is a spark at all, you need to unscrew the spark plug and apply it to the engine ground; this can be done using metal objects that are not covered with paint. You cannot hold it with your hand: if there is a spark, it can give you an electric shock, and the discharge reaches 40,000 volts, which the coil creates.

The functionality of the spark plug is checked in this simple way: you need to attach the spark plug to the metal body of the engine and turn the starter
If the spark plug does not produce a spark, it must be replaced with a new one; You can also check it using a special device that can be bought at a car store. It is inexpensive, it is a faster and safer way.
If the spark plug is working, but there is still no spark, you will have to use a multimeter, with which you can check the wiring of the scooter, find a break or a faulty element.
You also need to check the generator. It is an important element without which the scooter will not work. You will need to measure the resistance: to do this, you need to disconnect the ignition coil from the wiring, then measure the resistance between ground and the generator. This is usually a black wire with a red stripe. If the resistance is normal, it will be about 80-150 Ohms. If the device malfunctions, the resistance will be significantly less or absent altogether.
After this, you need to measure the resistance that the coil produces. To do this, a multimeter is connected to its terminals. One of the terminals is connected to the magnetic circuit. If there is no resistance, a coil malfunction is diagnosed. If it is there, but weak, it is worth checking the wiring or the place where the coil connects to it.
If everything is in order, but there is still no spark, you will need to check the wiring: to do this, you need to select two points to which the multimeter will be connected. One of the points should be the switch or ignition coil, the second should be the generator block. The wires may either be broken or there may be a short circuit between them. If the circuit is fully operational, check the ignition unit. It rarely fails, so it is dealt with last, when more likely causes of failure have been excluded.

Broken ignition is the cause of engine failure

An incorrectly configured or faulty ignition often causes engine failure. It would be wrong to immediately climb into the cylinder and examine the insides of the scooter, especially since this will not solve the problem. Before touching the ignition system, you need to check for other reasons why the scooter may not work.

The simplest thing is the lack of gasoline in the tank. Quite often, owners forget to refuel their vehicle, and such a trivial reason can be overlooked.
The carburetor may be clogged, which prevents the formation of a mixture suitable for driving.
The carburetor needs to be cleaned regularly, so it doesn't hurt to check whether fuel is flowing from it into the cylinder. It is possible that the fuel pipe is clogged. The jets and other parts of the device may become clogged with debris, which causes little fuel to flow or, conversely, the engine does not have enough air, and therefore it does not start.
The scooter may also refuse to start if the fault is caused by spark plugs. They may be wet or not produce a normal spark. It is advisable to have a spare set and check with it. In any case, the spark plug needs to be unscrewed and inspected.

This way you can visually determine the condition of the spark plug on the scooter.
If, after checking all the components, you are convinced that they are in order, you can check the ignition system in the manner indicated above and proceed to setting it up if everything is in order with the technical part.

Scooter tuning - air filter tuning

To properly power the engine, you need not only gasoline, but also air. Excess gasoline will do nothing for your engine unless it is enriched with enough air. To improve the air supply to the cylinder, special air filters are used. The most universal and balanced solution is to use a more efficient filter element, for example, Malossi Red Sponge, instead of a standard filter element. It is installed in the standard air filter box.

Another type of tuning air filters is the so-called zero-resistance filters (or simply - FNS). When installing them, the standard box is completely removed, and in its place is a small filter element, usually either cylindrical or cone-shaped. It has less resistance, which improves cylinder power at high speeds. However, firstly, these filters are almost not protected from external influences of dust, dirt and water, and secondly, unlike standard air boxes, they do not have a resonance effect. As a result, installing such a filter requires a thorough and precise reconfiguration of the carburetor, which only a few specialists can handle. If the service center tells you that they can “simplely” and “easily” set up a carburetor to work with the Federal Tax Service, most likely the qualifications of the workers there are below average. Leave and never come back!

How to increase the power of a moped

Over time, your favorite moped begins to lack power and you want the moped to go faster. Of course, you can sell your old one and buy a new, more powerful moped, but if you don’t want to say goodbye to your beloved two-wheeled friend, then you can slightly modernize the moped and add a little power to it so that it goes faster.

How to increase the power of a moped engine?

First, remove the plugs from the engine that were installed by the moped manufacturer. If you have a moped of Japanese origin, then first change the switch, it is where the main plug is located. A modified, tuned switch will remove restrictions and allow the engine to gain maximum speed. Before replacing the commutator, check the engine for wear on the crankshaft and cylinder-piston group bearings. On new models, special limiters in the muffler are often used; you can see how to remove the limiter from the muffler

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Scooter tuning - intake pipe tuning

The gasoline-air mixture prepared by the carburetor then flows into the crankcase through the inlet pipe. This part is sometimes mistakenly called a manifold, which is incorrect, since this pipe does not collect anything, but only directs the mixture into the crankcase. It is important that the flow area of this part is no less than the size of the carburetor, otherwise there is no point in installing a carburetor!

The flow area of the standard pipes on most scooters is such that you can easily use a 17.5 mm carburetor instead of the standard one. The same cannot be said about 19 mm carburetors! What can we say about such scooters, subjected to grief tuning with the help of 21 or even more carburetors without replacing the intake pipe!? Through tears, we call these “scooters named after the 19th carb”... An anecdote comes to mind: Stirlitz gave the dog gasoline and let him go. The dog ran 5 meters and fell. “The gasoline has run out,” thought Stirlitz.

Dismantling the engine 157qmj 150 cc

As you remember, I set myself the goal of disassembling the 157qmj piston engine without removing the power unit itself from the scooter.

So, we remove the carpet, the seat, the trunk (toilet), the plastic near the seat, and then the exhaust pipe, leaving the muffler in place.

I advise you to tighten all the bolts in place, since some of them are of different lengths, and it is simply impossible to remember the location of each of them!

Now remove the air filter assembly and carburetor. By the way, we will also replace the filter, since its throughput will be insufficient for a 170cc cubic capacity. Instead we will install a red 38mm UniFilter.

Removing the 157 QMJ carburetor is easy, just release the fuel hoses from the clamps, disconnect the throttle cable and the starter enrichment wires. We are also replacing the stock carburetor with a 24mm intake pipe.

The QMJ 157 engine is covered with plastic casings - this allows additional circulation of the cooling air flow and protects the engine from dirt. By unscrewing a few screws we can easily remove the plastic. I advise you to throw old rags on the floor, which would absorb drops of oil from the engine and also prevent dust from rising. The workplace must be clean!

We remove the cover with the rubber gasket of the 157 qmj gy6 cylinder head by unscrewing four 8 mm bolts. The breather hose that was originally connected to the air filter will now be connected to the new oil trap (more on that later).

We unscrew the four nuts (12 mm) securing the camshaft bed, cylinder head and cylinder. Carefully remove the upper part of the camshaft bed, holding it.

Before removing the camshaft, unscrew the chain tensioner adjustment cap and loosen the tensioner itself (with a small flat-head screwdriver clockwise) and remove the timing chain from the camshaft sprocket.

Unscrew the two bolts and remove the tensioner.

In order to remove the 157QMJ cylinder head, you need to unscrew two more 8 mm bolts. Carefully remove the cylinder head.

Remove the cylinder from the studs. The metal gasket cannot be reused.

Using thin pliers, remove the piston pin retaining ring and separate the piston and connecting rod.

Due to the greater height of the 4-valve cylinder head, it is necessary to replace the 4 studs on which the CPG and cylinder head are twisted.

How to correctly install the studs of a 157qmj cylinder? The original studs are unscrewed using two nuts screwed onto the stud. You need to unscrew the bottom nut counterclockwise. When screwing in new studs, lubricate the threads with blue thread sealant. The two bolts on the right side of the engine that secure the cylinder do not need to be replaced.

Scooter tuning - reed valve tuning

As a rule, a reed valve is installed directly at the inlet of the crankcase, also known as a “house” for its traditionally angular shape. However, not all reed valves have the characteristic “house” shape. The following engines use single reed valves as standard:

vertical Honda engines (primarily AF18)
almost all Peugeot engines (Trekker, Speedfight, Vivacity)
vertical Minarelli motors (Yamaha BWS, Slider)
as well as Morini (Aprilia SR 2000, Italjet Formula, Malaguti Crosser, Suzuki Sepia, Address)

It is these scooters that, first of all, require a tuning flapper valve, even when tuning the Sport class. In many other cases, you can easily use a standard valve, but with carbon petals. Of course, if we are talking about tuning of the Racing class and above, a tuning valve is required!

Modification of a Chinese scooter, a little about spare parts

Many scooter owners already after the first season have a desire to start modifying their pet . Tuning in our country has long become almost a national pastime. Owners of Chinese cars are no exception to the general rule. They try to increase their power, reduce weight, and improve other performance indicators of their pets. To do this, they equip their equipment with various additional parts. In addition, tuning can also include replacing standard components and mechanisms with better ones.

Basically, spare parts and components for Chinese scooters and other motorcycles are currently produced in Taiwan. In this country, scooters are treated with special love. Surprisingly, almost every Taiwanese has a scooter. In the production of spare parts and accessories for tuning, the Taiwanese use the best American and European technologies. Therefore, they are distinguished by a high degree of reliability and quality.

Almost all Chinese-made scooters are equipped with a 139QMB engine, an analogue of the Japanese Honda engine. All modifications are quite similar. Therefore, when tuning, there are usually no problems with installing various standard parts.

Scooter tuning - CVT tuning

Despite the fact that a variator is essentially the entire scooter transmission system, including 2 pulleys and a belt, in the world of scooter tuning the term “variator” is assigned to only part of this system - the moving (internal) part of the drive pulley. As a rule, installing any tuning part, for example a muffler, is quite simple, but often after installation new tuners are perplexed...

Why did the scooter start to ride worse? The answer is simple - the scooter is not configured. But even when more than a dozen tuning configurations made from weights and springs have been tried, it is not always possible to achieve smooth acceleration at constant speeds. This is where the tuning CVT comes to the rescue. By smoothing out failures in the transmission, it allows you to configure it optimally. Sometimes you can easily do without a tuning variator, but sometimes it is simply irreplaceable!!

Installing music

For a more fun and interesting ride, it is possible to install musical equipment, such as the option of installing speakers in the front panel or under the seat. Nowadays, it is not at all necessary to use a car radio; thanks to the development of electronics, it is possible to deliver a wide range of playback sources.

As an option: connecting the converter to the on-board battery and receiving a current of 220 volts. This allows you to expand your connection options even further. You can even use tuning accessories such as regular computer speakers that connect to any mp3 player via a 3.5 connector. And if they have the means, many deliver the amplifier. Everything is mounted depending on the design of the scooter, depending on where there is free space.

It is also possible to provide additional luggage compartment specifically for musical equipment or the transport of any small cargo.

Scooter tuning - impeller tuning

If on one side the belt in the drive pulley rests against the variator, then on the other it rests against the impeller. The impeller got its name for the additional function it has - transmission cooling. Tuning impellers have larger blades, allowing them to operate with greater productivity. Considering the low price of this part, we can safely recommend it for purchase. Sometimes, when installed with an appropriate variator, the impeller allows for a larger operating radius of the drive pulley, for example in the case of the Polini kit for the Honda X8R scooter.

Exhaust pipe

I would also like to note the options with changing the design of the exhaust pipe. Due to this, it is possible to achieve an increase in power and a change in the sound quality of the engine. There are two types of exhaust pipes: direct flow and resonator. Tuned models of exhaust pipes cost a lot of money, so some craftsmen, focusing on drawings from manufacturers, cook them themselves.

Also, in connection with tuning this element of the scooter, you will undoubtedly think about the design of the turbocharger. Read more about it here. You should also immediately deal with turbocharging. You can find this information in this article.

Scooter tuning - belt tuning

The role of the belt in the transmission of a scooter cannot be overestimated. By connecting the drive and driven pulleys, it is the belt that transmits torque from the crankshaft to the gearbox mechanism. As you know, the belt on a scooter is a consumable item and wears out quite quickly. When tuning, the load on it increases, so the wear process accelerates. A variety of manufacturers, right up to the tire giant Continental, offer samples that are more wear-resistant than the standard one.

Rigid Kevlar belts are not recommended for use with a standard CVT to avoid premature wear of the latter. The choice of belt should be approached very carefully, since according to the tests carried out, different belts can work completely differently in the same transmission. And sometimes, without appropriate settings, they can only worsen the dynamic and speed performance of the scooter.

Setting the valve timing ch2 (in collective farm style - ignition)

Without knocking the piston off from TDC, we orient the camshaft so that the large hole and marks on its sprocket become as shown in the photo and, while putting on the chain, install the camshaft in bed.

Ideally, the marks on the sprocket should be strictly parallel to the plane of the valve cover connector. In practice, unfortunately, such accuracy is difficult to achieve. And this is mainly due to the stretching of the timing chain. And there’s nothing you can do about it - either change the timing chain to a new one or catch the phase by switching the teeth, but this method of setting the valve timing is not acceptable to me personally.

Scooter tuning - gearbox tuning

What scooterists often complain about, even after a little tuning, is that they cannot reach the maximum speed. After all, when tuning the Sport class, the maximum engine speed increases quite slightly, which means that there is simply nowhere to get a significant increase in the maximum speed. However, the increased volume gives the motor more traction, which allows you to overcome hills at maximum speed, which previously could not be done without slowing down.

A new gearbox, or rather, gearbox gears, will help turn this increase in traction into additional km/h on a straight line. With their help, you can change the transmission ratio, thus increasing the maximum speed. Of course, the engine’s thrust reserve is not infinite, so you won’t be able to increase the maximum speed endlessly!

Scooter tuning - clutch tuning

The centrifugal clutch, installed on the shaft of the variator driven pulley, gives the scooter the ability to move away independently as the engine speed increases. Often, when tuning, the scooter receives a fundamentally new character of the engine and, in order to fully realize its capabilities, the clutch must operate at higher speeds. Sometimes this can be achieved by replacing only the clutch springs, but sometimes (as a rule, starting with the Midrace tuning and higher) you have to change the entire clutch. Tuning clutches have pads made of more advanced material, and also often offer more options for tuning - it all depends on the class of the selected product.

When tuning Midrace and above, the load on the clutch assembly is sometimes so high that in order to avoid overheating it is wise to replace the clutch complete with a bell, which is also offered by various tuning manufacturers.

We remove the engine.

Specialists, experts or garage technicians begin tuning a scooter with their own hands by dismantling the factory limiters. They are necessary to, firstly, keep the equipment within the established speed limits (Japanese models), and also to increase the service life of the motor. The problem is that you can find this element only after studying your engine model on various forums. The reason for this is the different locations of these same limiters, it could be a blind fork in the exhaust, an electronic limiter installed on the variator or even in the carburetor.

Plug in the variator. In this case, the part is a special plate mounted on the side of the weights. It prevents the belt from reaching its maximum radius, which means it is impossible to achieve the maximum possible speed. If you have such a part, then by removing it you can significantly increase the maximum speed.
Limiter in the variator. Sometimes the limiter is the lip on the bushing itself; here you cannot do without the work of a turner. By loosening the limiting edge of the variator, you can increase the speed. Also for many models a ready-made, bored part is sold.
Carburetor. In this assembly, the plug looks like a valve. With a significant increase in pressure, it opens, thereby preventing the full entry of the air-fuel mixture into the combustion chamber. This can all be treated as in previous options - by dismantling the element or replacing the entire part.
Exhaust. An interesting restriction system is located in the exhaust. It represents a branch where one of the channels is a dead end. Thus, turbulence and internal pressure in the exhaust increase, which prevents high-quality purging of the combustion chamber. The problem can be solved by brewing dead-end branches.
Electronic system. Finally, the switch limiter can be considered the most advanced by modern standards. Some Chinese and Italian models can be deceived by cutting the limiter wire, for this you will have to study a lot of literature on electrical engineering. Other models get rid of the problem by simply replacing the unit.