My Brother and I bought a mid 90's LT 80 for our boys to learn to ride on. The bike lookes clean and the guy I bought it from was an honest man. Supposedly the engine had been rebuilt once since the oil pump went out on it and fried the piston. He had been mixiing his own fuel at 40:1 with good oil ever since the rebuild. The quad ran strong when we first bought it and over the next few months seemed to lose more and more power. We wrote it off as a carb issue and as the bike started to run worse we just put it up as it was spring and they were tearing up the yard anyway. Now we got it back out and cleaned up the carb and it will not run. It gets great spark, the carb is getting fuel and it will not pop at all even with a shot of ehter to help it along. We pulled the plug and did a compression check and if the testor is right we got about 60psi which is terrible. How has this bike been running on such low compression or is there anything aside from the pistons being worn out that would cause the low compression. Right now I'm thinking we need to rebuild the quad but I want to check other avenues first before I head down that road. Calling the LT80 guru. I know you are on here. There are some young boys out there that would greatly appreciate some sage advice.

Thanks for the help guys you got an awesome resource here!

 

Welcome to the forums.
Only thing that could affect comp that much would be a blown head gasket.
If that is fine, then it's just wore out I guess.
Take the head off and see how the gasket is and how the piston and cylinder look.
Look for a .5 on the top of the piston. I'm guessing that is what it was bored to.
How did it run?? lol I've got machines in here that ran, and I could put the next size piston in w/o boring. They seem to run forever.
I'm wondering if they put the piston in backwards. It seems to happen alot. Arrow toward exhaust.
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It ran great as far as I can tell. I rode it for 20 minutes before I bought it. Up hills through fields crossing creeks. It ran about 30 mph with me on it going down a gravel road. I bet it only has about 6 tanks if gas through it since that day 4 months ago and now it won't run at all. I'll double check the compression numbers and pull the head if there is no change and inspect the gasket. Thanks for your time guys I'll keep you posted.