Engine Rebuild

[RamboHollow]

Tore the engine down and the seals where shot: You guys were right.
Have 90 PSI compression. Going to go on & replace rings & piston. Jug is going to have to be bored. Its hard to tell how munch it is going to take to clean it up. I know 1.0 MM over size will clean up. A .5 mm might.
Any draw backs with just going with the 1.0 mm?

Also any specs someone can give me or a copy of a G1 repair manual would be helpful.

Thanks for everyones help

[chuddly]

i gotta get my seals replaced as well (at least im pretty sure they are the problem) my cart is getting less and less throttle responce and its needing the choke more and more

[chompy]

I usually find that .25 oversize cleans up most cylinders unless there is extensive damage from broken rings. 1.0 is the largest you can go with OEM 2 stroke pistons (if that is what we are talking about here) so you might want to try something smaller in case you ever need to bore again. OEM oversize pistons on Yamis from G14s down meausre out on t 1/4 millimeter where's aftermarket pistons measure slightly smaller.

[sho305]

Chompy is right and not like you are going to see a power increase from that tiny amount of displacement. Messing with the porting and decking the head/etc....well that is the perfect time to do that if you want to.

[RamboHollow]

Its hard to measure. The guy thats going to bore it wants the piston before he bores: If I go with a 1.0 I'm sure it willl clean up. Its a G1 most likely will not rebuild again>

[sho305]

I was told a .25 would clean up a good looking used bore and .5 would clean up all but the worst. The G9 I'm working on they said .25 would be fine, the bore looks good but the oil ring let go and its got a lot of hours on it. But, we put a clone motor in it instead. I always put the piston at the top (if its ok) and move it around, if it moves a lot to and from the exhaust and not side to side, its egged out and will need more to get it round. Most of the time the bore is not bad even scratched due to the alum piston being much softer unless a ring tore it up or other parts got in there.