yz250f hard start after rebuild

before the rebuild i could start this bike with two kicks when it was cold, now it takes me forever to start it and it wont idle worth a damn. all i replaced was the piston, cylinder, and clutch. the timing was dead on when i put it all back together. never touched the valves. but i just pulled the spark plug out and its very brown, (to much oil i think) what do you guys think i should do? or check?

Did you overfill the oil??

1.5 quarts. but I've gone threw two oil changes.

Touch the valves this time.

Change your pilot jet

It sounds like the jetting needs to be changed. After the rebuld, that can be normal.

IF it was starting fine before the rebuild, and you didn't change jetting, I'd suspect something else. Replace spark plug, check valve clearance.......... .

Leak down test to check that you put all of your gaskets are sealing properly

Try a larger pilot....

Hows it ruin once it starts?

You know, I'm going through the same thing right now. I just got through a new top end, and had some similar issues, but I think I'm getting it resolved. In my situation, I think it's jetting. Previous to my new top end, I couldn't even touch the throttle when I kicked it. After the new top end, I actually have to give it a little throttle when I kick it. When I do, it usually starts within 2 kicks. Every 4 stroke I've owned has had little "starting tricks". After the new top end, it's kind of like I'm learning the bike all over again.

I also replaced the pilot jet and fuel screw. That seemed to help some.

Good luck.

what size pilot jet should i get? and i have a fuel mixture screw if you think that would help if i adjust it? how do i perform a leak down test?

I just got back from the track (1st time out since the top end). I put a 45 pilot jet in mine with an aftermarket fuel screw. Ran decent, but I think I have a little more work to do with the fuel screw.

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