Piston doesn't reach top of new cylinder

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one_and_only_norton

New Member
Sep 16, 2024
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I just replaced my bike's cylinder, piston rings, and clutch pads and tightened everything down, but the bike doesn't work now. The compression is extremely weak, and the cylinder is probably the cause (piston rings were installed properly, clutch was re-adjusted). I think the cylinder is bad - am i right?

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This is at the piston's highest point. i'm holding the cylinder down
 

Tony01

Well-Known Member
Nov 28, 2012
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sf bay area
Sounds like an improper combination of parts as well as possibly many other problems. You give us no information on your setup. What did you start with? Did it run? Why did you start changing parts?
 

one_and_only_norton

New Member
Sep 16, 2024
3
0
1
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Sounds like an improper combination of parts as well as possibly many other problems. You give us no information on your setup. What did you start with? Did it run? Why did you start changing parts?
It's a regular generic 80cc amazon motor. I first put it on an old mtb and it was great (30mph on stock sprocket, idles, everything is good) but i heard that aluminum frames could suddenly snap so I moved the motor to a steel cruiser.

I got a new cylinder since I stripped a carburetor screw (my fault) and new cluch pads since I read that black & white ones are stronger than the stock "eraser" pads.