Problem with my engine

Petter

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Oct 4, 2020
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I am having trouble with my engine and cant get it to run. I have bought the 80/66cc engine. I can’t really figure out the problem and I hope you can help me out. The thing is I can’t manage to keep it running. Every once in a while when I spin up the rear wheel the engine starts for a couple seconds but can’t seem to manage staying on. It seems like it can’t get anymore fuel after it has burned up the gas between the cylinder and the carburettor. I have tried several things, I have tried putting the engine in different angles so the jet can reach the fuel properly, I have tried tying up the bolts, and swapped spark plug. I am sure the carburettor gets fuel because I have drained it several times, and I’m sure the spark works as it can run for 3-4 seconds every once in a while. The clutch is also working perfectly, the piston is always moving when engaged. I have tried blowing through the jet and it is not clogged, also the black thing that moves when throttling up is usually moist so I think the fuel is getting there from the carburettor, but maybe not reaching into the cylinder. I have also tried removing the air filter to make sure it is getting air. I have tried spinning the wheel slowly and I can hear a slight “ssss” type sound. I hope its just the compression and think it is normal. I have even tried removing the exhaust and putting it back on but it doesent seem to make a different, as expected. I would just see if maybe the recistanse could be a factor.Do you have any ideas on what I can do, or look for? I would appreciate your help and I really want to get it to run properly. Here is a video. Thank you.
 
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Davideo

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Feb 25, 2020
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Try removing the spark plug and attach the high tension lead to it while grounding the threads on the cylinder head spin the back wheel you should see a strong spark jump across the plug's gap every time the engine makes a revolution. The last person with a problem like yours discovered that the coil was weak and not producing a strong enough spark to keep his engine running. A new coil solved his problem. Just a suggestion.
 

Davideo

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Feb 25, 2020
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After watching your video I have the impression that the engine could be flooding. Is there fuel spitting from the exhaust port? Try shutting of the fuel at the tank's petcock and get rid of the excess fuel in the engine by flipping it over with the spark removed.
 
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Petter

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Oct 4, 2020
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Hi, there is not necessarily fuel spitting out, but if I remove the sparkplug and look from a low angle I can see a small amount of gas that kind of looks like mist coming out of the cylinder. I also removed the exhaust after trying to start it for a while and there was a bit of oil in there. Does this give you any clues?
 

Davideo

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Feb 25, 2020
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Hi, there is not necessarily fuel spitting out, but if I remove the sparkplug and look from a low angle I can see a small amount of gas that kind of looks like mist coming out of the cylinder. I also removed the exhaust after trying to start it for a while and there was a bit of oil in there. Does this give you any clues?
The oil in the exhaust port suggests to me that either, the plug is not igniting the mixture because it is too rich (too much fuel and not enough air), or the spark is too weak to support combustion. Do the test for a strong spark as I suggested earlier and if there is a strong spark, shut off the fuel and keep turning over the engine until it starts.
 

Petter

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Oct 4, 2020
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Okay, but if this is the case how do i sort out
These problems? How do reduce the amount of fuel coming in to the cylinder? Is it the c-clip in the throttle? And how do I make sure the spark plug gives a more powerful spark? Thank you for your detailed and helpful responses.
 

Davideo

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Feb 25, 2020
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Okay, but if this is the case how do i sort out
These problems? How do reduce the amount of fuel coming in to the cylinder? Is it the c-clip in the throttle? And how do I make sure the spark plug gives a more powerful spark? Thank you for your detailed and helpful responses.
The mist you referred to earlier is normal, but if does not start immediately it will quickly flood the engine. In answer to your question about the mixture control, yes the position of the C clip on the needle determines it. The higher the clip the leaner the mixture, but the engine should run with the position set by the manufacturer. The answer is to eliminate the factors one at a time, first the spark and then the fuel. I will try to make a video later today demonstrating what a hot spark looks like.
 

Petter

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Oct 4, 2020
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Hi, i have made a video going through most of the bike as it might be easier to help me out. First of all excuse my English, it’s not my first language. Let me know if you spot the problem or simply want me to record something more/answer anything. Thank you.
 
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Davideo

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Feb 25, 2020
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Hi, i have made a video going through most of the bike as it might be easier to help me out. First of all excuse my English, it’s not my first language. Let me know if you spot the problem or simply want me to record something more/answer anything. Thank you.
Petter, first of all I found that the spark looks to be strong enough to support combustion and keep your engine running strong. The hissing sound suggests there is an air leak somewhere and it has to be fixed before the engine will run correctly. It could be the head is not tightened down correctly or simply the plug is not screwed tight enough into the head. You should also check that the carburetor is snuggly tightened on the manifold so that there is no air leak at that joint. The tank will be ok mounted on the parcel carrier as long as the fuel level is above the center of the carburetor. The spark plug is too clean it should be black with soot with a little grey area near the gap where the spark happens if the engine is running correctly. I am also wondering if there is enough air getting into the cylinder. Would you take a picture looking straight into the air intake. I want to know if there are any restrictions like a partially closed choke. My engine was loosing power the other day and I discovered that the choke lever was loose and was closing automatically. I used an elastic band to keep it open while running. Now it is running strong and producing lots of power as you can see in my video.
 
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Greg58

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Peter if you can move the tank back to the rear rack it will be easier to start if you can pedal it, as long as the fuel level in the tank is slightly above the carb the location is fine. Take the bike outside and pedal up to cruising speed before releasing the clutch, you may have to try different choke setting till it starts.
 

Davideo

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Feb 25, 2020
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Petter, first of all I found that the spark looks to be strong enough to support combustion and keep your engine running strong. The hissing sound suggests there is an air leak somewhere and it has to be fixed before the engine will run correctly. It could be the head is not tightened down correctly or simply the plug is not screwed tight enough into the head. You should also check that the carburetor is snuggly tightened on the manifold so that there is no air leak at that joint. The tank will be ok mounted on the parcel carrier as long as the fuel level is above the center of the carburetor. The spark plug is too clean it should be black with soot with a little grey area near the gap where the spark happens if the engine is running correctly. I am also wondering if there is enough air getting into the cylinder. Would you take a picture looking straight into the air intake. I want to know if there are any restrictions like a partially closed choke. My engine was loosing power the other day and I discovered that the choke lever was loose and was closing automatically. I used an elastic band to keep it open while running. Now it is running strong and producing lots of power as you can see in my video.
Petter, New engines like yours have some compression leakage because the piston rings are not fully sealed, that comes later during the running in phase. As Greg says you should not release the clutch until the bike reaches 10-15 kilometers per hour, then release it quickly. This is what I am doing in my video. If the engine is cold apply lots of choke and be prepared to remove after the engine begins to run; it only takes a few seconds of running for the engine to reach running temperature. These little engines require higher RPM before they develop their full power.
 
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Petter

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Oct 4, 2020
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Okay, thanks for the tip. I have made another video where i go through the carburator and cylinder head. At the end of the video I try to start it once again. Do you recommend trying to go faster and choking the the engine? The choke is at 50%. Aldo i want to add that i cant disengage the clutch. I have tightened it a lot as it was slipping, this have made it impossible to disengage the power. If I try to loosen it up it’s unable to connect fully with the piston. Does this affect the engine when I try to start it as I have to slowly speed up the rpm?
 
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Davideo

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Feb 25, 2020
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Okay, thanks for the tip. I have made another video where i go through the carburator and cylinder head. At the end of the video I try to start it once again. Do you recommend trying to go faster and choking the the engine? The choke is at 50%. Aldo i want to add that i cant disengage the clutch. I have tightened it a lot as it was slipping, this have made it impossible to disengage the power. If I try to loosen it up it’s unable to connect fully with the piston. Does this affect the engine when I try to start it as I have to slowly speed up the rpm?
Every thing looked good with your carburetor. The head on my bike is mounted the same way as yours, so no need to rotate it. You will have to adjust the clutch so that I can be disengaged with the hand lever. Maybe if you disengaged it during your starting run it would have run on its own There are many YouTube videos on clutch adjustment. I did notice one thing in your video that the tank outlet was above the fuel level within the tank so, if any duel was getting to the engine it was not very much so that could be another reason why you could not start it (fuel starvation). Lower the front end of the tank so the fuel can run out. Keep up the good work, it will eventually reward you with success.
 

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Petter

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Thanks for the tip, however the clutch is in horrible condition and can’t be fixed. The wire is as tight as it gets, and the screw on the clutch it self is tightened to the max, and it is still slipping. Therefore I have put some rubber between the screw and the clutch so it’s more pressure. This gets the engine at least engaged, but can’t disengage it. However, it’s a better solution than not getting it engaged at all. I have watched several YouTube videos on it and they all say I should just tighten the screw, but mine is already at max without the rubber. To me the fact that I can’t disengage the engine is not to important, but I still can’t get it started.
 

Davideo

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Feb 25, 2020
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Thanks for the tip, however the clutch is in horrible condition and can’t be fixed. The wire is as tight as it gets, and the screw on the clutch it self is tightened to the max, and it is still slipping. Therefore I have put some rubber between the screw and the clutch so it’s more pressure. This gets the engine at least engaged, but can’t disengage it. However, it’s a better solution than not getting it engaged at all. I have watched several YouTube videos on it and they all say I should just tighten the screw, but mine is already at max without the rubber. To me the fact that I can’t disengage the engine is not to important, but I still can’t get it started.
How will you stop your bike if it does happen to start and I am sure it is going to go if you get the right fuel air mixture. I do not know what screw you are referring to. Adjustment is accomplished with the (Flower Nut) while the hand lever is pulled in and held with the safety lock that holds the handle in that position. Did you reposition the tank so fuel can get to the engine (the fuel filter should be filled with fuel). Your video showed it practically empty.
 

Petter

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Oct 4, 2020
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Okay, I will make a video about it tomorrow explaining it a bit more detailed. I will sort out the tank problem, and also show you the problem with the flower nut. But check this out! I tried starting it in a pretty steep hill and I could clearly hear it fire. What do you think?
 
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