has anybody tried that p-38 thing for the ac.pump cover ? does it work?

loads in the archives. just put the words in the box & read on!


Yes, I installed the P-38 in my 2000 426 and it has made a huge improvement. I find that it has performed exactly as claimed by Factory R&D. My 426 carburates as perfectly as any 426 out there. It starts easily whether hot or freezing cold, never fouls a plug, never hesitates, hiccups, spits, stalls, and the throttle response is INSTANT. I can wick the throttle wide open right off idle and the engine revs cleanly and super quickly. Can't ask for better that that.

I guess I should read the past post (I will). What does the P38 do? I thought I heard it provided a different accel pump stop. Does it provide more or less fuel? Is it the same part for 00 and 01 bikes?

Originally posted by mikeolichney:

What does the P38 do?

It changes the stroke of the acc. pump because the bottom is raised higher (so you are right about the pump stop). I suspect the ’01 FCR accomplishes the same thing with a diaphragm with a longer metal stopper in the insert but the new diaphragms aren’t available yet. But I also read that the pump stroke was altered by changing the cam or actuating arm at the throttle pull. At any rate all the diaphragms for ’01 are different PNs than ’00.

So I don’t know what the effect would be of installing the P-38 in conjunction with the ’01 diaphragm or if they will redesign the part for the ’01. As far as I know this part is identical for all applications (KTM, DRZ, & YZ/WR).

I’ve also read that the P-38 atomizes the fuel charge better due to a smaller outlet, but this doesn’t make sense because the final nozzle is integral to the carb body and should be the smallest orifice in the passage. James Dean called Factory R&D asking about the product and posted their responsehere on the WR side of Thumpertalk.

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