2000 yz125 rebuild

[DoghouseCR250]

Just put the top end back on my yz125 and am getting nothing. Haven't cheked compression but it feels good. Never had this prob. before, and am clueless as to what happened. Any ideas?

[twostroker]

did you put the piston is backwards?

[DoghouseCR250]

Nope. That's one of the things I'm always mindful about.

[TUK101]

Well man, gas spark and compression are what is needed to fire her off. Which one of those things are missing? If you have all 3 then you need to start thinking about timing, fuel delivery (jetting, reeds), clean air filter, crankshaft seals, etc. One other thing to think about, did you get the power valve hooked back up right? I dont know if that would keep it from firing, but it might? How about the wires to the carb, are all of those hooked up?

[DoghouseCR250]

I know I've got spark and fuel, gotta get my compression gauge tomorrow from my shop... That's the only thing left really. I guess I'll know after that. If it's not compression though, I haven't a clue.

[DoghouseCR250]

I'm officially an idiot. The brand new spark plug I put in yesterday apparently was bad. It would fire when held to the side of the case but not under compression apparently! Put the old one back in today and started on first kick.

[The Baron]

Good news!