History of the 139QMB engine
The largest and most popular category is four-stroke engines, the most popular and famous among which is the 139QMB model. The first model of the 139QMB engine was developed in the 90s. Ten years later, the development was used by China for mass production of engines. The final version, after numerous modifications, has become one of the best engines for motor vehicles: today Japan is actively involved in its purchase and subsequent sale under the Honda brand.
Engine Features
The official manufacturer of the 139QMB scooter engine is Hongling Corporation, which equips motorcycles not only of its own brand, but also of other brands with this engine.
The corporation sells power units to other manufacturers. The motor itself is very recognizable: the design features of the 139QMB engine and its markings on the left side of the crankcase immediately make it clear what kind of heart beats the scooter.
The motor has no flaws, does not require special treatment and calmly tolerates minor negligence and negligence. The manufacturer provides a guarantee for its products that covers the first 5 thousand kilometers. This mileage is enough for the new 139QMB 4t scooter engine to fully run in and grind in all elements and components of the systems.
The total service life of the engine is about 20 thousand kilometers, with the exception of 5 thousand running-in at an average driving speed of 90 km/h. The technical characteristics of the 139QMB engine are not bad: its power is enough for a two-seater full-size scooter.
What are the most reliable scooters: what to look for
It is necessary to approach the choice of an “iron horse” with special responsibility. After all, by purchasing a low-quality product, you risk harming not only your health, but also the health of the people around you. In addition, riding a poorly assembled moped will not bring you proper pleasure.
The motor is the first thing you need to pay attention to. After all, almost everything depends on the choice of the type of internal combustion engine: from the durability of the device to its behavior on the road in dense traffic.
Power is also an important indicator, on which not only speed, but also the level of its maneuverability depends.
Analogues - engine 1P39QMB
Chinese developers have created an analogue of the Japanese 139QMB engine - a motor labeled 1P39QMB, which in appearance completely replicates the original. Despite all the similarities, you can still find differences: the valve clearances on the 1P39QMB are not adjustable. The situation is similar with the carburetor: before direct operation it requires thorough cleaning and correct adjustment. Chinese copies of 139QMB engines, of course, cope with their task, but their main purpose was to reduce the final cost of motor vehicles. Budget versions of scooters are equipped with exactly the same versions of engines that are good only for short trips at low speeds.
Before starting operation, be sure to carry out a full run-in of the 1P39QMB engine. The optimal operating mode of the engine begins only after 2 thousand kilometers, but after 10 thousand kilometers all its technical characteristics drop, and it loses dynamics and power.
Engines 157QMJ
In addition to the very popular model - the 139QMB engines - Hongling Corporation produces other versions of power units, one of which is the 157QMJ. It is installed on expensive scooter models of famous brands. In terms of its technical parameters and indicators of functionality and reliability, this version is a complete analogue of 139QMB. In addition, the design features of the model are strongly reminiscent of other mass-produced Japanese engines.
The advantage of the 157QMJ is its increased service life - about 25 thousand kilometers. The engine boasts powerful dynamics and a high top speed. However, it also has its downside - the price is too high compared to previous versions of the engines.
Which engine is better, 4-stroke or 2-stroke?
Let's start with a 4-stroke engine, I'll start with the fact that this engine is more reliable than a 2-stroke engine. Moreover, it works quieter than its counterpart, and is softer, that is, practically without vibration, such an engine can confidently travel at least ten thousand kilometers, I repeat, minimum, because it has a modern lubrication system like a car, where oil is poured directly into the engine
and lubricates better than a 2-stroke engine
Where the crankshaft bearings are literally bathed in oil, and the piston and rings are lubricated by an oil pump.
And such an engine is much more economical, but it has its disadvantages, and this
- 1: Expensive and difficult repairs
because there are many more parts in it, and it is structurally more complex
- 2: You need to monitor the oil level
because if there is no oil, the consequences will be bad, that is, the engine will simply seize
- 3: After a certain mileage you need to adjust the valve clearance.
- 4: Low power
such an engine is weaker than a 2-stroke engine, since all 4 strokes work there
Well, in my opinion, there are only four minuses now about the 2-stroke engine
So why does everyone love the 2-stroke engine so much? Well, of course, because of its powerful engine. The working cycle of a two-stroke engine occurs in one revolution of the crankshaft, which makes it possible to extract 1.5-1.7 times more power from the same displacement at the same engine speed. And of course its design simplicity, that is, disassembling such an engine will not be difficult.
Engine D1E41QMB
The D1E41QMB motor is the only two-stroke engine model made in China. A distinctive feature of this engine from other representatives of the category of power units is the presence of a chain reverse gear in the design. The uninterrupted operation of such an engine is ensured by mixing gasoline and oil in proportions of 40 to 1. The working life of the engine is about 10 thousand kilometers, after which the need for repairs arises. The disadvantage of the engine is the forced speed limit - no more than 50 km/h.
Which is better: two-stroke or four-stroke internal combustion engine
When choosing this vehicle, the first thing you should pay attention to is the structure of the engine. It comes in two types: two-stroke and four-stroke. Recently, most scooters have been produced with a four-stroke internal combustion engine. Such machines are characterized by reduced consumption, quiet operation, and ease of operation. Also, such devices have an increased level of environmental friendliness. But they have one significant drawback that repels buyers - high cost of maintenance.
Two-stroke engines are unpretentious to fuel and operating conditions. Such scooters pick up speed faster, that is, they have increased unit power. In addition, they are much cheaper than mopeds with a 4-stroke internal combustion engine.
Cons of a two-stroke engine
The disadvantages of two-stroke internal combustion engines include:
increased fuel consumption;
unnecessary hassle when refueling (gasoline must be mixed with engine oil);
a large amount of exhaust gases.
Running in the engine
Incorrectly carried out running-in of the 139QMB engine in most cases leads to failure of the piston system. Friction occurs between the parts of the new CPG, which leads to an increase in engine temperature.
Running in the scooter motor is carried out as follows:
- The scooter is placed on the center stand.
- Within 5 minutes the engine starts at idle speed, the field of which cools down during the same time.
- Over the next 10 minutes, the engine also runs, after which it cools down for 15 minutes.
- The engine is restarted for 15 minutes, then turned off and left to cool for 15 minutes.
- The scooter is started again for 30 minutes, after which it is turned off and left for 20 minutes.
After carrying out such manipulations, you can run in the scooter itself. In the first 100 kilometers of the journey, you should not turn the throttle handle more than 1/3 of its full stroke. The maximum speed should not exceed 30 km/h. The speed can be increased by 15–20 km/h for the next 300 kilometers - during this time the engine should more or less reveal its potential.
After this break-in process, the oil must be changed.
Engine valves are adjusted every 500 kilometers.
Engine tuning
The first thing they try to change when tuning the 139QMB engine is the cubic capacity. For this purpose, the standard piston system is replaced with an 82cc one. At the same time, a new cylinder head with enlarged valves is installed. The piston system changes along with the camshaft, since a larger amount of fuel-air mixture is required for its correct operation. A new camshaft will help increase the volume of the incoming fuel mixture, but the carburetor will still need to be replaced.
Which scooter or moped is better for an adult to buy – Japanese or Chinese?
It is believed that the best motorbikes are new ones, and it does not matter in which country they were made. But many people will disagree with this statement. After all, a certain stereotype has long been established in the minds of Russians, according to which goods produced in China do not differ in special quality indicators.
Products from Japan are famous for their high reliability indicators. But there is a certain disadvantage - they are quite expensive. If we compare the products of these two countries, a new moped from China will cost about the same as a used Japanese one. Therefore, in this situation, the choice remains solely with the buyer: if he is 100% confident in the serviceability of the used Japanese car, then naturally the choice is obvious. Otherwise, it is best to take a Chinese one. As for repairs, it will be much cheaper for you to fix the latter.
Air filter
It is not recommended to completely remove the filter element or replace it with a zero-resistance filter - this can lead to contamination of the carburetor. Experts usually recommend removing the plug that is installed at the inlet of the air filter.
Many reviews that affected the assembly of the 139QMB engine after tuning talk about installing a zero-resistance air filter. Despite the fact that this solution is one of the most popular, it is not always appropriate and justified.
The reason lies in the fact that installing such a filter leads to rapid contamination of the carburetor. The main reason for using a zero resistance filter is the need for a richer fuel mixture after installing a larger piston. However, this can be avoided by installing a new camshaft and replacing the jets in the carburetor.
Separately, it is worth noting that a standard carburetor equipped with a 16 mm diffuser is installed together with a 62–72cc piston system, while the 82cc piston system is equipped with a carburetor with an 18 mm diffuser.
For replacement, it is advisable to purchase a set of jets, since several different options may be needed to adjust the carburetor.
Which Chinese motorbike is better to choose?
Those who do not have the opportunity to buy an expensive unit from the land of the rising sun can choose a scooter from cheaper Chinese products. But it is very unlikely that it will serve you for very long.
SYM is a fairly common technique. Among other brands, China is distinguished by its durability and level of reliability.
KEEWAY is an inexpensive representative of the Chinese motorcycle industry. The key to long-term operation lies in choosing good fuel.
Irbis is a bike with an aggressive, sporty design. Inexpensive to maintain.
Why you shouldn’t choose 2t mopeds from China
As mentioned above, Chinese bikes do not have a high level of build quality. Therefore, during their operation, mopedists constantly encounter problems. In addition, there are several factors that will constantly haunt you when using such products:
almost complete lack of engine thrust;
increased fuel consumption;
constant need to clean and replace spark plugs;
reduced overall resource of the internal combustion engine.
Variable speed drive
It is possible to increase the efficiency of a standard scooter variator and use its full potential only after installing an enlarged belt. At the same time, a set of new weights is purchased - they should all differ in weight. For a CVT, the required weight of the weights is selected extremely carefully and painstakingly, since the maximum speed of the motor vehicle and the dynamics of its acceleration depend on them.
