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1976 Yamaha GT80

01 Apr 2020 06:39
mmmmsass4
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1976 Yamaha GT80 #1
My GT80 bogs badly and is impossible to start. There is very little resistance on the kickstarter and compression is low. I want to do top end and replace piston & rings plus replace all gaskets on motor. My piston is stamped with "50" on dome, I don't see any other markings. Can someone with more knowledge than me assist with what size piston I should buy or point me to a supplier?
THANKS!

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01 Apr 2020 07:53
Gr8uncleal
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1976 Yamaha GT80 #2
Welcome!

50 usually means 0.5mm oversize. For Yamahas that (again, usually!) means second oversize.

Check out your bike on Partzilla or CMSNL to see what oversize Yamaha produced for that model. However, before ordering anything, get your engineer/reborer to have a look at it in case it needs to go two more sizes up.
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