2. Install crankshaft engine at TDC compression stroke:
remove the plug from the viewing window in the engine cooling casing;
The direction of rotation of the motor is clockwise from the fan side. Scrolling not allowed crankshaft counterclockwise direction!
Rotating the crankshaft and combine the "T" mark (at different manufacturers in different ways) on the generator rotor with a ledge on the crankcase.
3. Using a feeler gauge, we measure the gap between the pusher and the valve stem. For 50-100 cc engines cm, valve clearances 0.03-0.07 mm.
4. Loosen the locknut of the pusher adjusting screw.
5. Rotate the adjusting screw with pliers while simultaneously controlling the gap with a feeler gauge. The gap is set correctly if the probe moves in it with resistance, but not freely and does not wedge between the valve and the pusher.
6. Holding the adjusting bolt with pliers in the set position, tighten the lock nut.
7. Once again we control the correctness of the gap setting.
8. Adjust the clearance at the second valve.
9. Install all removed parts in reverse order.
Next article.
When you need to make adjustments.
♦ The scooter does not start or starts with difficulty.
♦ Gaining momentum with difficulty.
♦ Constantly stalls.
♦ The motor makes a ringing noise.
Attention, not only improper valve adjustment can cause these problems. Description of common problems possible reasons occurrence and remedies will be published on our website.
Attention:
♦ Gap adjustment only ON A COLD ENGINE!
♦ Remove the seat carefully, the plastic is brittle, especially when low temperatures!
♦ It may be necessary to adjust the carburetor after adjusting the clearance.
♦ Before removing the cylinder head cover, it is advisable to wipe the engine. After removal, make sure that foreign objects do not get into the engine.
♦ For possible harm caused by incorrect adjustment, the author of the article does not bear any responsibility.
Required Tools:
♦ Pliers
♦ Phillips screwdriver
♦ 9 and 8 mm wrenches (heads)
♦ Feeler gauge for setting the valve clearance (we will need 0.05 and 0.1 mm)
Step 1. Preparatory work.
Prepare 3-4 jars or other containers for screws, nuts and other small parts. So we will not lose anything in the process of work.
Removing the seat. Here we need a 10 mm socket wrench and a screwdriver. IN luggage compartment there are 4 nuts that need to be unscrewed (two on the sides of the seat lock and two on the bottom). There are 2 screws under the rubber foot mat, which we also unscrew (see photo).
Step 2. Fan cover.
To adjust the valves, we must find the top dead center.
To do this, remove the plastic fan cover for the generator:
We unscrew 2 nuts (M8) and two screws and remove the lining:
Step 3. Cylinder head cover.
Removing the cylinder head cover:
To do this, unscrew 4 M10 bolts and 2 nuts (a metal tube is screwed with nuts). Now we remove the cover and see the following picture:
The arrows indicate the valves: at the top is the inlet, at the bottom is the outlet. Before we start setting the gap, we need to find the TDC (top dead center).
Step 4 Top Dead Center (TDC)
TDC is the point at which the piston in the cylinder occupies top position. In this article, I present a method for finding TDC using marks on the generator rotor. Of course, you can determine the TDC in another way, for example, by the position of the rocker arms. Attention: Four-stroke scooters have 2 TDC!
There are 3 holes on the camshaft sprocket. Their location shown in the photo corresponds to the TDC of the piston, at which both valves are closed (what we need).
On the flywheel of the generator, the risks are beaten: T (TDC) and F (ignition moment):
The T mark must be opposite the ledge marked with the number 1.
To align the protrusion and the TDC mark, use a socket wrench and rotate the fan CLOCKWISE until TDC is reached. To find out that this is really TDC, we gently move the key, while the valve rockers should not move. If they move, then this is not TDC, we turn the fan further, CLOCKWISE, until the risk and the ledge are combined.
Well, we have found the top dead center, now you can start adjusting the valves.
Step 5: Adjust/Check valve clearance.
To check the clearance, we take a 0.05 mm feeler gauge and try to stick it between the intake valve and the adjusting bolt.
If this fails (due to a lack or slight gap) or the gap is too large, then loosen the M9 locknut and turn the adjustment bolt with pliers or a suitable wrench. Clockwise - the gap decreases, counterclockwise - increases. At the same time, hold the probe between the valve and adjusting bolt.
The probe should fit snugly between them so that the probe can be moved, but should not be scratched when moving. Tighten the locknut while holding the adjustment bolt with a wrench or pliers. After tightening, check the gap again.
So we set up the intake valve.
Do the same with the release valve. Access with a probe to it is difficult, but possible. The gap here should be 0.1 mm.
Done with valve adjustment. We assemble in reverse order, put all the parts in place. (head cover, fan cover, seat).
Let's see if we haven't forgotten anything. All screws, bolts, nuts are tightened accordingly. We work with plastic carefully! May break, especially at low temperatures.
Well, everything is ready, fair wind to you!
Tool:
Pliers, Phillips and minus screwdrivers, open-end wrenches for 8, 9, 10, 11, 12 and (heads) as well as 13, 14 probe for setting the valve clearance - Inlet valve 0.05
And Exhaust valve 0.10 mm.
Valve clearance adjustment- the procedure for a new scooter is mandatory, and this must be done as soon as possible after purchase. Then about every 2500 - 3000 km. But if a characteristic clicking sound, similar to a clatter, is heard from the cylinder head earlier, you should not wait for routine maintenance. If possible, for the first time, adjust the gaps together with someone who has already done this more than once. But this is optional. ATTENTION! Adjusting the valve clearances of the scooter is done only on a COLD engine, since these clearances are thermal.
So, let's begin.
To begin with, we will free access from the cylinder head cover. To do this, remove the seat (toilet). You should get a picture, as in the picture. At low ambient temperatures, plastic must be handled with care as it becomes brittle.
Now unscrew the screws (1) securing valve cover(2). If there is a tube, we dismantle it.
Now you have such a picture in front of you - valve cams, rocker arms, camshaft, camshaft sprocket.
Now to adjust the valve clearances you need set top dead center (TDC) piston, i.e. catch the moment when the piston is in the upper limit position. It is not difficult. But be careful: four-stroke engines have two TDC, at the beginning of bars 1 and 3. We need a 3rd beat.
To find the TDC, remove the fan cover for the generator. Turn the key to 13 clockwise hexagon on the generator cooling impeller until the risk on the generator flywheel with the “T” mark matches the protrusion on the side of the flywheel.
Now look at the camshaft sprocket. Two small (1) and one large (2) holes should be positioned as shown. In this case, the valves must be closed, and with a slight oscillation of the generator flywheel, they must not move. The so-called position of the "3rd measure", or rather, the beginning of this measure.
Now you can proceed directly to adjusting the gaps. First you need to check the gaps. Using a 0.05 mm probe, we check the inlet (upper) valve - we insert the probe between the adjusting bolt and the valve. With a normal setting, the probe should enter with little difficulty, and you need to move it in the gap with a little effort, but so that it does not leave scratches on it.
If adjustment is required, loosen the locknut ("outside"). Then you can change the gap by rotating the adjustment bolt (“inside”) - less in h / s, more against h / s. Then, without releasing the adjusting bolt, tighten the locknut. Here you need to be careful - after tightening the locknut, the gap may change. Therefore, we recheck the clearance.
Do the same with the release valve. Only access to it is more difficult, and the gap is 0.10 mm.
All. Now we collect everything in the reverse order.
Sources - the book "Repair and maintenance of Hongling scooters", A. Velichko, T. Beremtsev; some photos: china-scooter.com
During work four-stroke engine air cooling(such engines are on most Chinese scooters and motorcycles) the cylinder head (hereinafter referred to as the cylinder head) can heat up to 260 degrees. This is of course not working temperature, but the peak is often just that.
The valves that are located directly in the cylinder head itself heat up in the same way as the head, with the only difference being that the intake valve heats up a little less as it cools working mixture, and she is an ordinary atmospheric air saturated with gasoline vapours, and Exhaust valve heats up a lot more. Since the flow of exhaust gases passes through the exhaust valve, the temperature of which can reach 600 degrees.
The problem is that metal parts expand when heated. Valves are no exception: during operation, the valve heats up and becomes a little longer. And when the valve becomes longer, it simply rests against the gas distribution mechanism and opens a little, or rather it does not close completely (clamped) due to which gases under high pressure seeping through leaks melt the working edges of the valve and its sockets.
The edges of the burnt valves look something like this.
By the way, not only the valves burn out, but also the sockets in which they sit
And this is how the working edges of valves and seats look like after repair.
As you can see, it makes little sense to regulate what has been burnt out for a long time. A burnt valve will no longer hold compression. And if you find that one of the valves has been clamped, then feel free to remove the head, grind the valves, otherwise there will be no sense.
gaps
Here is the combustion chamber of the engine of an ordinary Chinese scooter.
During engine operation, the valves heat up to significant values. And in order to compensate for the expansion coefficient of the valve and the entire timing as a whole, there is a small gap between the valve and its opening mechanism. called thermal.
In our case, the gap that we will adjust is between the valve and the rocker arm adjusting bolt. By tightening the adjusting bolt within the required limits, we can adjust the thermal gap as much as we need.
But do not forget that the gap should not be very large - otherwise the mechanism will work with a shock load and quickly fail. And very small: the valve will heat up, rest against the rocker and burn out.
Preparation
From the foregoing, you probably understood that the thermal gap exists in order to compensate for the thermal expansion of the timing parts. From this follows the most important rule: You can adjust the thermal gap only on a cold engine. If you start adjusting the heat when hot, then simply increase it, since the initial gap will go to expansion. And when the engine cools down, the gap adjusted in this way will double. I hope this is clear.
Tools
- Small pliers or special wrench
- Open-end wrench for 9
- 14 socket wrench or socket
- socket wrench 8
- A set of measuring probes preferably with a pitch of 0.02 mm
We release access to the cylinder head: depending on the model of the scooter, we remove the hood or the seatpost. We look for the valve cover there, unscrew the four bolts by 8 and remove it from the engine.
The valve cover looks like this. In my case, to get to it, I had to remove the hood, saddle and seatpost capacity.
- we remove it. If you are too lazy to remove it, we only remove the plug from it. The plug is located in the upper part of the housing and is removed with a conventional screwdriver. Through the plug we will control the position of the marks on the rotor.
We insert a socket wrench into the center of the generator casing by 14 and turn the engine (clockwise) until the “T” mark (from the English “Top” means top, in our case the position of the piston at TDC) on the generator rotor is exactly opposite the ledge.
After the mark on the generator coincides with the ledge on the engine crankcase, we check in what position it has become camshaft. The camshaft should be in a position where both valves are closed. And he becomes in this position every second revolution of the crankshaft, since it rotates twice as slowly.
Correct position camshaft identified by its asterisk. The sprocket should become a large hole upwards, and the small holes and the risks that are knocked out near them should become parallel to the plane of the valve cover connector.
This is ideally, but in practice the asterisk rarely becomes the way we need it. And the chain is often to blame for this - and the camshaft begins to slightly catch up with the crankshaft. If your asterisk has become a little crooked, then by and large - this is nonsense. But if you don’t understand how it has become, then this problem needs to be solved very quickly - otherwise sooner or later the valves will bend.
Once again, we control that the “T” mark on the generator rotor is opposite the protrusion, and the camshaft sprocket occupies correct position. We unscrew the locknuts on the adjusting bolts.
We unscrew the adjusting bolts a little, insert a measuring probe between the valve and the adjusting bolt and without removing it - tighten the adjusting bolt with our fingers, clamp the adjusting bolt with pliers and fix it with a lock nut.
After tightening the locknut, check how easily the feeler gauge moves. Ideally, the feeler gauge between the valve and the bolt should move with barely perceptible force.
- If the probe moves without effort, loosen the locknut and tighten the bolt a little.
- If the probe moves with difficulty or is pinched, loosen the bolt.
Gap size
What I don't like about Chinese scooters so it is that they do not have any adjustment data. There is information on the Internet about this, but it is not always reliable.
You have the right to believe me or not, but for my clients I adjust the gaps within the following limits:
- On engines of the 139QMB series (ordinary Chinese eighties), I put a gap of 0.05 mm - both on the intake and on the exhaust valve - the same.
- On engines of the 157 QMJ series (ordinary Chinese hundred and fifty), I put 0.05 mm on the intake, and 0.07 mm on the exhaust
Periodicity
It is advisable to make the first adjustment immediately after buying a scooter, both new and used. The remaining adjustments should be made after 3000 - 4000 km of run.
Introduction.
From time to time for 4 stroke scooters the valves need to be adjusted. To do it yourself or in the service, everyone decides for himself. I would like to note that adjusting the valves on a scooter is not such a difficult thing, anyone who knows how to turn the nuts can handle it ... This process will take 20-30 minutes in time. All you need is attention and care.
When you need to make adjustments.
- After the first 500 km of run, then - according to the table indicated in the instruction manual of your scooter.
Most often, a reduced or increased valve clearance leads to the fact that:
- The scooter does not start or starts with difficulty.
- The engine is slowly picking up speed.
Also, the engine keeps stalling.
- The motor makes a ringing noise around the head.
Attention:
- Valve clearances are only adjusted ON A COLD ENGINE!
- When removing the seat, be careful, the plastic on scooters is very fragile, especially at low temperatures.
- It may be necessary to adjust after adjusting the gap.
- Before starting to remove the valve cover, it is advisable to wash the engine with water in the area (cylinder head) and wipe it dry. After removal, make sure that foreign objects do not get into the engine.
Required tools:
- Pliers
- Crosshead screwdriver
- Keys 9 and 8 mm (heads)
- A feeler gauge for setting the valve clearance (we need 0.05 and 0.1 mm). The dipstick can be purchased at any auto shop. It is best to have a similar set in your garage, as shown in the photo below.
This is what the valve gauge looks like.
To adjust the valves, we must find the top dead center (T.D.C.) of the piston. To do this, remove the plastic lining of the generator fan:
We unscrew 2 nuts (M8) and two screws and remove the lining:
Step 2. Cylinder head cover.
Remove the cylinder head valve cover:
To do this, unscrew 4 nuts M10 and 2 nuts (the tube is screwed with nuts crankcase gases). Now we remove the cover and see the following picture:
The arrows indicate the valves: inlet at the top, exhaust at the bottom. Before we start setting the gap, we need to find the T.D.T. (top dead center).
Step 3 Top Dead Center
V.M.T is the point at which it occupies the upper position in the cylinder. This article discusses the method of searching for V.M.T. using marks on the rotor a. Four-stroke scooters have two MTs! (upper and lower)
There are 3 holes on the camshaft sprocket. Their location shown in the photo corresponds to the T.M.T of the piston, in which both valves are completely closed (what we need).
On the flywheel of the generator are marked risks: T(V.M.T) and F(ignition moment):
Risk T should be opposite the ledge indicated in the figure by the number 1.
To align the protrusion and the T risk, it is necessary to turn the engine CLOCKWISE using a socket wrench. To find out that this is really V.M.T, we gently move the key, while the valve rockers should not move. If they move, then this is not V.M.T, we turn the fan further, CLOCKWISE, until the risk and the protrusion are combined.
Well, the top dead center has been found, now you can start adjusting the valves.
Step 4: Adjust/Check valve clearance.
To check the clearance, we take a 0.05 mm feeler gauge and try to stick it between the intake valve and the adjusting bolt.
If this fails (due to the absence or too small gap) or the gap is too large, then loosen the M9 lock nut and turn the adjustment bolt with pliers or a suitable wrench. Clockwise - the gap decreases, counterclockwise - increases. At the same time, we hold the probe between the valve and the adjusting bolt.
The feeler gauge should sit snugly between them so that the feeler can be moved, but the feeler should not wedge when moving (i.e. the feeler should be slightly pressed by the adjusting bolt). Tighten the locknut while holding the adjustment bolt with a wrench or pliers. After tightening, check the gap again.
Inlet valve - adjusted.
We do the same with the release valve. Access with a probe to it is difficult, but possible. The gap here should be 0.1 mm.
Valve adjustment is complete. We assemble in the reverse order, put all the parts in their place (head cover, fan lining and the rest of the plastic).
ATTENTION!
It should be remembered that the clearances given in this article (taste 0.05mm and release 0.10mm) are applicable for Chinese engines with a volume of 50-80cc (cube). For scooters with a 125-150cc (cc) engine, other clearances are provided for inlet valve 0.07mm, and for graduation 0.10mm.
