HELP !! 08 yz 450 f

Got to the track. Bike started 2nd kick, as usual. took off on track. Hit the first jump. Felt like a bog on take off. Almost like something was blocking the exhaust pipe . 1/2 a lap, coasted in. Bike died. I changed plug. Plenty of fire. Tore down carb(3 times:bonk: ) Nothing. Bike wont start at all. I checked timing, by looking at the mark on the cam and it was TDC. ANY CLUE? Any where to start? What about the sensor for the carb? I am new to Yamaha and I am not sure if they have a notorious issue or not Any ideas before I start tearing it dow? Thanks

Do you have spark?

spark would be good to start with?

sounds to me like the valves

you either have a major or radical change in valve spec

tear the top off and check them

Spark is good

If the spark is good, and the timing and compression are good, then it's a fuel issue.

Yeah, could be a fuel flow issue. Check your tank breather valve, could be malfunctioning

Checked the fuel breather line and the gas cap(just in case). I would think if it was a valve issue, it would make some sort of noise, don't ya think? That dang honda would make a noise if the valves were out by .001!

I appreciate you guys taking the time to try to help me. If I ever get to the bottom of it, I will let you know.

Thank you again


check float level in carb

that'll make it bog and not start

also check ur jets one may be clocked with a small chunk of dirt that'll do it also

is the gas on?

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