Post-Rebuild Help!

[phireboi]

Well I just rebuilt my 400ex, and put all new valves and piston/rings, gaskets and all and after I got it all back together and put oil and everything in it, I tried to start it up and it won't, I charged the battery to make sure that wasnt it, now every once in awhile trying to crank it, it'll just make a huge backfire but not attempt to start, Anyone have any ideas what my problem could be?, I thought it might be bad gas too but I put fresh gas in it too.

[Chanman420q]

well im assuming that it is cranking over....

First off, make sure your kill switch isnt over. Sounds stupid but even ive freaked out because my quad wouldnt start, just to relize the kill switch was on.

Then, id check to make sure your plug isnt fouled and the air filter is clean. If the plug isnt fouled, then make sure your getting spark.

If its still a no go, check your timing. That could be a problem. Hope u didnt bend a valve.

Last thing to check is, that gas is getting in the cylinder. if not, clean your carb out. Make sure your jetting is good too

[BLEEDRED]

Is it possible that you weren't at true TDC when you put it back together. Make sure that your cam isn't 180 degrees out. I've seen that happen before.