Best Year 450 Carb for a 1999 400F???

Hello all! I'm looking to update the carburetor on my old '99 400F with a carb possibly from a 450. Is there a carburetor from a particular year that lends itself to a good fit with the 400? Anybody with recent experience who can give me an idea would be greatly appreciated. Thanks for any help in advance:thumbsup:

The best ones are the latest ones. The '05 and later are the most sophisticated FCR's yet. Try to get throttle cables and the hot start cable/plunger with it. These are a direct bolt-up fit to a 426, but some have said that the 450 carb is slightly shorter front to rear than the 400, and that made it necessary to stretch the air boot a little to get it into place.

Otherwise, you will need to plug the vacuum port on the head that serves the 400 hot start system, and that's it.

the one on the left is off a YZ426F, the other one is off a 07 YZ450F

yz426_yz450_carbs.jpg

I haven't noticed any difference when getting the airbox boot on the 07

You didn't read what I said. The reports of air boot misfit were for a 400. I just said the 450 carb bolts directly up to a 426.

You didn't read what I said. The reports of air boot misfit were for a 400. I just said the 450 carb bolts directly up to a 426.

Confirm that. I'm running an 05 carb on my 99 WR400 and the boot need to be stretched to fit.

Thanks for the advice Gray as always, you're a lot of help. Currently I am looking into a Carburetor from an 08 model. SXP, is there anytime the boot has worked its way off since it has to be stretched on, or is this not really a big deal? Did you just transfer the jets from one carb to the other or was there a need to rejet all over again? I heard that some jets are different in the newer carbs. Is there anything else I need to swap other than the cables, such as the throttle handle? Sorry for all the questions, just wanted to see if you could offer any first hand advice. Thanks again, I appreciate it all:worthy:

Did you just transfer the jets from one carb to the other or was there a need to rejet all over again? I heard that some jets are different in the newer carbs. Is there anything else I need to swap other than the cables, such as the throttle handle?
The hot start on the 450 carbs is cable operated, and integrated into the carb. Try to get the complete plunger, cable, lever, etc. along with it. If you can't get the lever. you can buy a used lever set from a 450, or buy and aftermarket hot start lever, or the pieces to convert yours to the late style.

The throttle cables are different, but they fit the old twist grip just fine.

As far as jetting goes, the jets are different because of differences in the carburetors, not the motorcycles. You may have to rejet, but start with what comes in the carb as a baseline. The '06 carb I sold to a guy here had 100% stone stock OEM jetting in it, and he dropped it on the bike and siad it had never run as well as that, ever.

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