Yamaha Champ questions

Dale L /

I have a Yamaha Champ 50cc that I put 3 different jugs/pistons in, and still can't develop over 50 lbs compression. I put oil in the cylinder and can get 135 lb compression for about 5-6 revolutions, then back to 50lbs again.

Can anyone tell me the standard bore size, size of piston, and ring end-gap?

Any help would be appreciated to get this running. Thanks.

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