I have another bike Grubbe Skyhawk 66cc, with more problems :/

Redm777

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The bike is smooth, while going fast, but once I pull the clutch in it revs super high then low then high, and once I pull out the clutch at a stop sign, the motor revs super low and accelerates super slow, then eventually gets some speed. My chain also or something makes a terrible scraping and clicking sound when I hit the coaster brake, I know its nothing wrong with the bike because I took off the chain and no sound or anything happened. And as of now, the bike is not running either, it just stopped mid-ride.....
 

Cisco

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When you slow down or use the brakes, are you disengaging the clutch? Under deceleration, there is a lot of tension on the lower part of the chain. It will make a lot of noise as it rolls across the tensioner wheel. It's best not to use the engine to slow down (that's what the brakes are for). The inconsistent RPMs could be from an air leak. First check the carb and intake. Also check the crank seals. The magneto seal is often the culprit. Does the inside of the magneto case look oily?
 

Redm777

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When you slow down or use the brakes, are you disengaging the clutch? Under deceleration, there is a lot of tension on the lower part of the chain. It will make a lot of noise as it rolls across the tensioner wheel. It's best not to use the engine to slow down (that's what the brakes are for). The inconsistent RPMs could be from an air leak. First check the carb and intake. Also check the crank seals. The magneto seal is often the culprit. Does the inside of the magneto case look oily?
yes i do disengage the clutch and use brakes I have rear pads, and I use a coaster for a smooth stop. Also the carb, I have it on with no air leaks against the intake. I put high temp red gasket maker on the intake area and re rightened the studs and put it back on. Edit: I don't use chain tenioner and I have good clearance of chain also
 

DAMIEN1307

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I don't use chain tenioner and I have good clearance of chain also
Did you at least take out links on the chain for exact fit like the pic of my drive chain shown in pic ???

IMG_0352.jpg
 

Cisco

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The magneto seal is often the culprit. Does the inside of the magneto case look oily?
My PK80 had that runaway RPM problem. It wouldn't idle down, and would race and die. I notice oil on the garage floor leaking out of the magneto side of the engine. When I looked inside, I could see that the seal had come completely out. The seal on that side is only 3.8mm thick, easily comes unseated if not set properly to begin with.
https://motoredbikes.com/media/sealleak_01.114652/
https://motoredbikes.com/media/sealleak_02.114653/
 

weefek

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I'm at about 10 or 15 km with the same kit, I've noticed the same noises from the chain while going slow. I have a spring loaded tensioner that I've modified in order to work properly so it's easy to see what the chain is doing.

I've noticed the drive sprocket teeth on these engines are way too square. This is where the noise is coming from. Without the proper chain tension they are terrible. My chain was initially way too loose and the chain was insanely clicky on the drive sprocket. Now with proper tension its only clicky at low speeds but im hoping over the break in period the drive sprocket will wear in such a way to eliminate this otherwise I will either find a new one or reshape the teeth
 

Nickt919

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If you're sure the alignment is correct, then just put some miles on it. It should quiet down. Try a little more or less tension on the spring tensioner. I've found there's like a sweet spot on my spring load tensioner where the noise is less.
 
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