Rebuilding the top end on YZ250F

[Flybuy994]

Okay, I'm pretty desperate right now, I really need help! I'm rebuilding a buddies '03 YZ250F. The top and bottom end seized up because he ran it with no oil. Well, I had a bottom end off of a 2004 YZ250F laying around so I told him I would sell him that, install it, put on my '04 cylinder, install new Wiseco piston/rings, and use his cylinder head and valves.

Everything was going smooth until I tried to start it. The bike has perfect spark, and alot of compression. But, it is getting no gas. So I check to make sure I timed it right, perfect(I've timed a YZF before and had zero problems). I check the valve clearances, perfect. Try to start it again, still nothing. So I take the carburetor off and clean it, still no gas on the plug after a thousand kicks.

So I take off the carburetor and spray gas directly into the cylinder head with a squirt bottle. Well that works, it gets gas. So does this narrow it down to my problem being in the carburetor? I'm thinking that if the intake valves were not opening and I sprayed gas directly into the cylinder head, then it would still not get gas, right?

Please help!

[Flybuy994]

Also the carburetor actually sat around for 5 months before I got to it, so it keeps looking likely that it is the carburetor.

[avlnch]

Could the carb be gummed up?