low compression?

[Cray]

ok i just an 82 yz125 motor put back together and it aint hit a lick yet.. has excellent spark and fuel seems to be getting into cylinder.. but the cylinder is a hair out of round and the piston has to much side clearance, i mean way to much.. i put a compression gauge in the plug hole and held the throttle wide open while kicking and got about 87lbs of top end compression.. is this poor comp for a 125 or normal.? i would think it would at least fire but maybe run like crap with bad comp, but it wont even fire at all.. im goin to wynoka dunes this next week end and id really to get this thing goin long enough to take it.. any advice or tips would be apreciated..

 

[r_rider28]

87lbs? it will never run. 150-170 would be enough to get it going. Did you put the rings in it?

 

[Glitch]

Like r_rider said, it will never run. Take the cylinder off and get it bored by a shop and have them get a piston for it too. Hopefully you can find a shop that can do it it time and get the piston in time. If you take it to someplace on monday, have them order the piston that day and try to bore it asap, you should have everything at latest friday, hopefully.
Also, riding in dunes with a 125 is a bad idea. The engine will overheat from all the stress from trying to keep it going in the sand.

 

[Cray]

ya i figured that was probably the problem.. i bought another cylinder from ebay and it was shipped yesterday, was kinda hopin i could use it and just get it bored to fit this piston, its a new piston i paid 5$ bucks for.. but looks like its gonna have to wait.. i never been ridin in the sand before but i didnt really think it would bog a bike down that bad, so maybe i shouldnt be worried about gettin this thing runnin now anyway..
thanks