If you were lucky enough to buy a 50cc scooter, you've probably already thought about how to get the most out of it. For almost every scooter rider, top speed remains a priority, and most models cannot boast of sufficient power. Considering the widespread availability of models with a capacity of 50 cubic meters and their limit of 60 km/h, the question of how to increase the speed of a scooter is quite reasonable. Naturally, there is a solution to this problem.
As practice shows, minor tuning can increase the top speed by 10-15, and in some cases, by 20 km/h. The main thing is to understand which motorcycle settings will be as convenient and simple as possible for independent implementation. You need to figure out how to increase the power of a 50cc scooter and get a real increase in speed, without unnecessary problems.
How to increase the power and speed of a moped
Many scooter owners, after a few months of riding, think about the question “How to increase the speed of the scooter?”
And no wonder! After all, the notorious 50 “cubes” are often not enough, and it is not possible to quickly raise money for new, more powerful equipment. That is why various tricks are used to increase the power of the moped, as well as its speed from the usual 60 km/h to 80 and above.
Safety is the main factor
If you decide to increase the power of your outboard motor , then do not forget that:
- additional forces do not always give a noticeable increase in speed;
- excessive engine power can make the boat not very stable, especially on sharp turns;
- it may become less manageable.
The motor power should not exceed the permissible power specified in the boat’s passport. And understand that by increasing power, you reduce the efficiency and service life of your boat.
Procedure
There are several effective ways to increase moped performance such as speed and power. The most popular of them should be described:
Under them you will find a belt responsible for transmitting speed to the rear wheel and both sprockets. Above this belt you will see a small metal washer (speed controller) that limits the belt to a larger radius.
You need to knock this puck down with a hammer, and then try to pick up speed. If your moped has an engine capacity of up to 75 cc. see I was able to accelerate to 70–75 km/h, which means you succeeded.
With proper modification of the scooter, you can increase the maximum speed of the vehicle to 120–140 km/h, however, for this you will need to attach a new washer, which will protect you and will not create difficulties during the technical inspection.
The higher the puck is, the higher the scooter's speed will be. Try to empirically find the position of the washer at which the max. the speed would be 95–100 km/h.
The only disadvantage of such actions will be a natural decrease in traction, as a result of which you will not be able to normally drive up hills with an inclination angle of 20 degrees or higher.
Motor assembly 157QMJ
Installation of gaskets and rings
The most important part of the assembly was making sure the spacers and rings were aligned correctly. Pay attention to the channel in the cylinder - install the gasket without blocking this channel, as it allows oil to lubricate the cylinder head. The gaskets were treated with a special Hylomar sealant, which provides a good seal and prevents engine oil leaks.
compression rings have a designation (T1 - upper, T2 - lower), with which they need to be installed towards the top. The bottom three rings (not marked) form the oil scraper ring, a wavy ring sandwiched between two metal rings. All three rings must be placed so that the gaps between them are at a distance of 120º. This can be achieved by conditionally dividing the piston into three even parts (approximately like the letter Y). The main thing is to ensure that none of the ring spaces coincide with one another, to prevent compression and oil leakage.
Now you need to carefully install the piston along with the rings into the cylinder. I advise you to lubricate the inner surface of the cylinder with a small amount of oil.
Lubricate the paper gasket with sealant 30 minutes before installation, align it with the holes and channels and install the cylinder on the studs. Make sure the piston is installed with the IN designation facing the intake manifold.
After the hole in the piston for the pin and the hole in the connecting rod coincide, we install one cotter pin in the piston, and on the other side we advance the piston pin until it rests against the lock ring. Then install the second cotter pin. You need to carefully check that the retaining rings are securely seated in the grooves on the piston - there is no need to take risks here! I recommend initially lubricating the piston pin with engine oil.
After making sure that everything is installed in accordance with the requirements described above, we push the timing chain through the window in the cylinder. While holding the cylinder, make sure that the piston moves in the cylinder freely and without jamming (to do this, rotate the crankshaft by hand using the generator bell). I advise you to set the piston to top dead center and see if the T mark on the generator bell matches the projection on the engine. If it doesn’t match, draw a new mark with a marker and use it in the future. In this case, the mark does not coincide with TDC.
Other options
In addition to the above method, you can increase the performance of a moped such as its power and speed using other tricks. For example, you can increase the power of your scooter by replacing the muffler, replacing it with a compatible resonant pipe, and tuning the transmission.
You can also choose a sports variator for your scooter and install a reinforced belt .
If you don't know how to further increase the power of your moped, try replacing the standard exhaust pipe with a sports one. With its help, you will increase the power of the scooter by up to 15%, increasing the maximum speed. Finally, replace regular brakes with disc brakes, standard brake pads with sports brake pads, and select brake hoses with reinforcement.
After all the work involved in trying to increase the speed and power of the scooter, do not forget about your safety and the safety of other road users. If you doubt the correctness of your modifications to the moped, contact the service, where they will give you practical advice or carry out a set of improvements yourself. Remember that your life may depend on the quality of work to increase the power and speed of equipment.
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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.
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:
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.
In fact, there are only four main areas of boosting a scooter (I will list them in the logical sequence of modifications made):
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).
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.
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) .
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.
Tuning of Chinese scooters 2t, 4t, 50cc, 150cc
Writing about tuning scooters is like ignoring Kozma Prutkov’s warning and trying to embrace the immensity. Therefore, in this material I will touch on a narrow and topical topic - tuning four-stroke “Chinese” ones.
First, I’ll warn you against possible reproaches, like Chinese technology cannot be tuned, it falls apart on its own, etc. So, in large letters: THE CHINESE MOTOR INDUSTRY, IN THE PERSON OF ITS BEST REPRESENTATIVES, HAS GROWED TO THE SOLUTION THAT ITS MOTORS DO NOT FALL UP AFTER THE TUNING PERFORMED ON IT. At least right away. Realistically, without joking, this is an achievement; if you had written like this a couple of years ago, they would have laughed at you. Another digression - a few lines of educational information, this is for those who are far from the topic, or have just embarked on this thorny path. Experienced tuners (or tuners - as you like, but not to be confused with toners and tuners) can skip this block without damage to themselves.
LIKBEZ Globally, scooter tuning can be divided into measures for: – increasing engine power , from removing standard “stranglers” (if any) to, first of all, increasing its cubic capacity; – transmission settings for changed engine parameters or when the manufacturers themselves “messed up” (that is, they did not properly adjust the variator). In both the first and second directions, the components and parts for tuning two-stroke and four-stroke engines are fundamentally different. What I mean is that it would be nice to know what it is.
Here is a short list of what they usually put their hands on when professionally tuning an engine: CPG, that is, the cylinder-piston group (it includes a piston with a cylinder, and the pin, rings, stoppers like them), cylinder head, carburetor, air filter, exhaust system and reed valve (for two-stroke engines), electronic ignition unit. In the transmission, the following are subject to tuning: the variator clutch assembly, weights, belt, rear half-pulleys, driven pulley spring, springs and the “bell” of the centrifugal clutch. In addition, they carry out tuning of the chassis (suspension, tires, brakes) and decorative tuning, also known as styling. And one more thing: it is impossible to achieve tangible results (except perhaps with a minus sign) by tuning one engine and without interfering with the operation of the transmission.
Now let's move on to what is on our market. I think I won’t discover America for anyone (but I can’t help but say this): all Chinese “air” four-stroke engines are practically the same. Their prototype was a Honda engine coded GY6. What is it?
Here it is, the original - the Honda GY6 engine.
As you know, Honda Motor Company improved the design of the scooter engine in the 1960s. Relying on that technology, the more advanced Honda GY6 engine was produced in the 1980s. It is four-stroke, single-cylinder, air or air-oil cooled, standard with two overhead valves. Power in the stock version of 125-150 cc models ranges from 7.8 hp. (5.8 kW) to 12.4 hp (9.2 kW). And forced engine modifications can develop up to 14 hp. at 12,000 rpm.
The GY6 engine is coupled with an automatic CVT transmission (variator). This engine was initially produced in capacities of 50, 125 and 150 cm3 and was installed on scooters of the (CH125/CH150) Elite and Spacey families.
The execution of “125” and “150” differs slightly from that of “fifty kopecks”.
Scooter of the CH125/CH150 Honda Elite family.
Today, Honda no longer uses these engines in their scooters (they have moved on - liquid cooling, fuel injection), but Chinese, Korean, and Taiwanese clones of this engine are produced in huge numbers. In China alone, where there are more than a hundred scooter companies, each has a copy of the GY6 in its arsenal. Because of this engine's widespread suitability and low cost, Asian ATV manufacturers began using GY6 clones in their children's ATVs and buggies (from road go-karts to off-road vehicles), 150cc youth quads, and even children's snowmobiles.
Due to the wide distribution of the engine in both older Honda models and new Asian imports, you can find a lot of information on the Internet about modifications, available components and parts. User forums such as buggy news go karts and off road buggy forum or scootdawg forum allow you to discuss the problems of these engines, repair methods and tuning (though for those who are fluent in English). Users on these forums have experienced many modifications from third party countries, such as four-valve heads with high compression ratios, big displacement kits, upgraded CVTs, CDI racing ignition units, carburetors, and exhaust kits.
I would like to express my respect to Chinese manufacturers: the country has introduced a clear standardization system in designations, and all manufacturers follow it. Otherwise there would be such confusion! Here are the basic types of Chinese scooter engines : 139QMB (bore x piston stroke 39x41.5 mm, displacement 49.6 cm3), 152QMI (52.4x57.8 mm, 124.6 cm3) and 157QMJ (57.2x57.8 mm, 148.5 cm3). As you can see, in their digital code, if you remove the one, the diameter of the cylinder is encrypted. Within each type, the main parts of the cylinder-piston group (CPG) are interchangeable, and with minimal tolerances. That is, you can safely install parts from one manufacturer on a unit from another. Thanks to this property, you don’t need to bother searching for parts (either for repair or for tuning) for any specific brand.
Lifanovsky clone 152QMI.
Now, perhaps, about the most important thing - who produces the desired sets and how accessible they are .
Previously, advanced scooter riders were familiar with tuning kits (they are also called “whales”, from the English Kit - set) of Italian (Polini) and “Malossi”. Their range is extensive, it includes not only repair kits and tuning kits for European two-stroke scooters, but also for common Japanese cars. However, all this tuning from “Malossi” is expensive, from “Polini” it is even cooler, despite the fact that the “whales” still sailed from China and Taiwan. And besides, today there are an order of magnitude more new “Chinese” on our roads than vehicles from Europe or Japan. It is not surprising, therefore, that “whales” began to sail to us from Asia directly, and not from Europe, bashfully covered up by famous European brands and at European prices. Let everyone know where the tuning drummers live - on the island of Taiwan. Why in Taiwan? There, the highest degree of scooterization of the population (21 million scooters per 25 million inhabitants) has given rise to a special attitude towards this technology, and Japanese and European technologies make it possible to maintain a high level of production. In addition, the lack of heating costs and people’s unpretentiousness in everyday life and food make the price of products humane even for such a poor country as Russia has become. Remember these brands Koso, CM Racing, YMS Racing, RPM, NHRC, perhaps they (or dozens of others) will soon surpass the “Italians” in popularity.
Cleaning the cylinder from carbon deposits and filing down the cylinder window
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).
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.
Safety
When making any independent reconfiguration of engines, you must not forget about basic safety rules:
- If the motor is overpowered, the boat can become very unstable.
- It will either capsize or simply throw passengers overboard during a sharp turn.
Therefore, if you decide to improve your purchase, you should not abuse modern innovations. You always need to compare the technical characteristics of the boat with the possible maximum permissible power.
Before each long-distance departure, do not forget to check the serviceability of all parts and the integrity of the boat itself, because the safety of passengers and the driver himself should always come first.
Chinese scooter tuning and prices
Scooters produced by foreign manufacturers have a number of design limitations. First of all, the restrictions relate to the speed and power of the engine. For European consumers, the scooter's speed is limited to 50 km/h. Scooter tuning is designed to remove these restrictions. For what? To break traffic rules? Not at all.
The factory-limited power helps the engine operate in a gentle mode. And, consequently, its service life increases, the mechanical load on components and mechanisms decreases. Tuning scooters or tuning a moped definitely reduces the reliability and life of the engine .
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.
