Help: 2009 YZ450F

Alright guys I've got a problem with my bike bogging when landing from a jump at wide open throttle. The bike runs great and doesn't ever bog on the stand or anywhere else in the throttle range, only at full throttle when landing, when I'm pushing 100%. It doesn't happen every lap but about 10 times throughout the day. This gives me a very uneasy feeling and today I came very close to getting spit over the bars.

I've checked the obvious things like making sure all my carb lines are not plugged and that the gas tank vent is working. I also raised the float height .050 from what the manual calls for and raised the needle 1 clip. This did not help.

Any suggestions on how to eliminate this problem? I seen that Dicks Racing sells a deep well float bowl nut which is supposed to cure the problem. Anyone have expirence with these?

I've searched all over the internet but can't seem to find any answer about this problem. Everyone else has the bog when opening the throttle quickly.

Does it bog as the throttle is being opened, or stumble as the bike lands even after the engine has already responded?

It bogs on impact after the bike is revved out.

I never have any issues when opening the throttle quickly in any conditions.

That suggests a situation in which fuel is moving away from the main jet. This would be because the slosh control in the bowl is inadequate, or because the level is low for some reason, possibly due to a flow interruption caused by being momentarily weightless.

Things like the deeper bowl nut usually don't help because the jet isn't extended deeper into the new space. An aftermarket float bowl might help matters, though.

I have very limited knowledge on jetting but I have an 09 with a R&D Float bowl and I have not experienced any bog at all. But I also have a Dr D full exhaust. I bought it used with the goodies already on it so I can't comment on the before and after of the float bowl.

Edited by Hoosier-Daddy

Don't know where the icon came from. R and D float bowl

Thanks for the suggestions guys. I'm gonna try the deep well float bowl nut since I can get it for $20. If that doesn't work I'm gonna bite the bullet and try the R&D powerbowl. I had one on my 2012 YZ250F, I should have removed it before I sold the bike.

I searched the internet again today and it seems that this is a very common problem but I never read where there was a definitive fix. The only post I seen where it was fixed was with raising the float height but it's already higher than the factory setting. I may try to raise it again slightly before getting the R&D bowl. Is there any negative effect of raising the float bowl besides puking gas out of the overflow? I can still lean the bike way over before it comes out of the overflow after raising it the first time.

Update: Alright guys the rain finally stopped and I was able to get out and spin some laps on the bike yesterday, although I had to drive 6hrs to a track that was open. It was worth it though cause it was the legendary Monster Mountain!!!

The bike ran great with no bog on the jump landings or hiccups whatsoever. The changes that I made were an FMF Powercore 4 slip on and a Tokyo Mods deep well float bowl but.

I originally ordered a Dicks Racing float bowl nut but sent it back after I didn't like the way it was made when it arrived. After more searching I found the Tokyo Mods nut which in my opinion is made of much better quality. It has about 10 little holes below the threads to let fuel in and the Dicks had none. The factory nut has 2 holes.

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