Problem with my engine

Petter

Member
Oct 4, 2020
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So I did some riding today, I have now put 9 km on the bike, it’s running fine but it got some small issues. First of all the chain bounces up and down when I ride, (I don’t know if it’s normal but it is shaking a lot up and down with a distance of maybe 2 cm), however when I go fast (30 km/h) it runs in a nice line. I don’t know if it it’s either normal or a problem, but it seems odd.

Secondly, the oil leak haven’t stopped. It’s a lot better now that I have reduced the oil percentage, but it’s still spitting out oil around the cylinder exit (this might be because the gasket ripped and I’m using a old thin metal one).

Third of all, the tank haven’t completely stopped leaking. I put some paper around it last night and today it was pink, indicating the leakage. It’s only leaking from around the exit part of the tank, but I drips and hits the wires and runs down to the carb. This is annoying as I’m loosing fuel, and it’s making the bike dirty and wet.

The last problem is very weird. I have now experienced it three times, and don’t know what’s causing it. Sometimes when I ride it simply just goes full throttle and I can’t stop it. Even if I pull the throttle back and fourth it’s just sitting there at max rpm. I then have to shut it off with the killswitch. When I start riding again it’s fine. This is very weird and can be problematic as it gets loud if it’s just idling and can just take off all of a sudden.

I hope you can help me out with any of these problems.
 

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Davideo

Active Member
Feb 25, 2020
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Thanks for the tip, I am happy with 30 km/h but I have seen other bikes go faster so I was just wondering if there was something wrong.
I am sure that after the engine has properly run in things will free up, the compression will gradually increase and it will begin running smoother and faster. The thing to remember at this point is to avoid over revving or running too long at the same speed, but vary the speed up and down. It is also important to avoid disassembling or disturbing the components such as the piston and cylinder head, the quality of fit is improving during the running in period, even carbon build up will help improve compression.
After you are finished the running in phase you may get better performance by playing with the needle valve.
 

Petter

Member
Oct 4, 2020
33
16
8
18
I am sure that after the engine has properly run in things will free up, the compression will gradually increase and it will begin running smoother and faster. The thing to remember at this point is to avoid over revving or running too long at the same speed, but vary the speed up and down. It is also important to avoid disassembling or disturbing the components such as the piston and cylinder head, the quality of fit is improving during the running in period, even carbon build up will help improve compression.
After you are finished the running in phase you may get better performance by playing with the needle valve.
Cool, thanks for the Information. Did you see my post about the issues? If so, you got any tips?
 

Davideo

Active Member
Feb 25, 2020
166
148
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83
If it's reving on its on it has a vacuum leak.
I have experienced this overrevving myself and I discovered that it is due to fuel starvation. The engine is burning fuel at a faster rate than the it is being delivered to the carburetor. In my case the problem was getting enough fuel through the petcock and filter to the carburetor. The flow rate has improved slightly but I am starting to suspect the Ethanol fuel that I have been using.
 

Davideo

Active Member
Feb 25, 2020
166
148
43
83
So I did some riding today, I have now put 9 km on the bike, it’s running fine but it got some small issues. First of all the chain bounces up and down when I ride, (I don’t know if it’s normal but it is shaking a lot up and down with a distance of maybe 2 cm), however when I go fast (30 km/h) it runs in a nice line. I don’t know if it it’s either normal or a problem, but it seems odd.

Secondly, the oil leak haven’t stopped. It’s a lot better now that I have reduced the oil percentage, but it’s still spitting out oil around the cylinder exit (this might be because the gasket ripped and I’m using a old thin metal one).

Third of all, the tank haven’t completely stopped leaking. I put some paper around it last night and today it was pink, indicating the leakage. It’s only leaking from around the exit part of the tank, but I drips and hits the wires and runs down to the carb. This is annoying as I’m loosing fuel, and it’s making the bike dirty and wet.

The last problem is very weird. I have now experienced it three times, and don’t know what’s causing it. Sometimes when I ride it simply just goes full throttle and I can’t stop it. Even if I pull the throttle back and fourth it’s just sitting there at max rpm. I then have to shut it off with the killswitch. When I start riding again it’s fine. This is very weird and can be problematic as it gets loud if it’s just idling and can just take off all of a sudden.

I hope you can help me out with any of these problems.
Addressing the problems from top to bottom:
Petter said (I don’t know if it’s normal but it is shaking a lot up and down with a distance of maybe 2 cm)
This is due to slack chain which is not constant because the rear sprocket is not perfectly concentric, that is why I prefer a spring loaded tensioner which is capable of maintaining constant chain tension.
In your case the shaking stops because at 30 km per hour the centrifugal force of the chain riding on the sprocket tightens the chain and removed the slack. This is why every thing smooths out at high speed .

Secondly, the oil leak haven’t stopped
It probably will never stop completely but soon it will be so small that you wont worry about it.
The thing you have to resolve quickly is the fuel tank leak. find out where it is coming from and seal it or drain the tank and get another one.

The last one I already talked about.
 
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Davideo

Active Member
Feb 25, 2020
166
148
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I bent a wheel avoiding our dog, I had to whip the bike sharply, It was either wheel repair or hitting a 80lb Lab and doctor/vet bills.
Sorry to hear of your accident. Dogs and bikes are usually an accident waiting to happen. I hope you escaped without hurting yourself or your Lab.