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KX450 won't start

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I just finished rebuilding the top end on my new '07 KX450f. I've rebuilt a crf450 a couple times before but this is the first time I've done a KX.

Just put in a new cam chain, piston/rings, SS intake and exhaust valves with springs. I lapped the valves and the intake's sealed up perfectly. The exhaust had a very slight leak (slowly got wet when filled with carb cleaner). It feels like there's good compression when I kick it but I don't have a compression tester that fits the hole.  All 4 valve clearances are within spec but all on the tightest setting. I triple checked timing of cams and they're perfect.

It's got spark but when I spray starting fluid down the spark plug hole, it doesn't come close to starting.

Suggestions?  I really don't know where to start

Thanks in advance

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3 hours ago, Scottwr12345 said:

Air boot blocked? Carb clean? Thats where id start

I cleaned the pilot and main jet. I didn't dissassemble the carb though.

But it wouldn't start when it is sparking and I put starting fluid in so it has to be a compression issue, right?


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So I decided to take apart the carb and clean everything. I found a broken piece that connects to the accelerator pump. IMG_1589.jpg

Also the o-ring around the air/fuel screw was shredded. I wouldn't think that either of those things would prevent it from starting but of course I ordered one ones.

Jetting was 180 main, 42 pilot, 70 (not sure what that jet is called), and the needle was in the 4th clip from top. The whole bottom part of the carb and accelerator pump (the bowl?) is red and stamped "R&D". Not sure if the needle is stock or R&D.

With the carb off, I sprayed starting fluid into the intake on the head and kicked it several times and it wouldn't act like it wanted to start.

Is that normal?? I would think it should fire up like a banshee....

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