P-38 Lightning

It is a replacement bottom to the APJ housing, with a raised bump stop to restrict the movement of the diaphragm and hence the amount of fuel "Squirted" into the carb when you open the throttle.

There are various mods around that acheive the same result, for a LOT less coin, with a LOT more ajustability,

I dont know which mod applies to which year apart from the "Taffy Mod" for the 99's

There is the BK and the KL mod, do searches on these and a lot of questions should be answered :)


The P38 and/or the BK mod used to be almost mandatory for 400s and early 426s. The accelerator pumps were way too aggressive. They don't improve a bike with a reasonable AP squirt volume and duration, which your 2002 is likely to have. Only if you have an AP problem would you look into these on a new bike.

Good luck,


Will the P-38 Lightning do anything for a 2002 WR426? Is it a waste of money? Is it even designed for the 2002?

it works good on my 98 wr

what is it?

Freestyle 111

Did you change jetting as well when you installed the P38?

The Taffy mod and KL mod are the same and apply to 98/99's. This is where you limit the travel of the AP rod by using a RC airplane wheel, axle collar. The collar will only allow the rod to move appx .024-.030" before it hits the AP housing. You can find the collar at most hobby type stores. Cost $1.39 for four collars and a wrench.

The BK mod is for the 2000 and later bikes and uses a screw tappen into the bottom of the AP housing to limit pump rod travel.

The P-38 does the same thing and is $40ish???



I found the collars. They called them duralock collars. My question is when this collar is installed it only allows for .024-.030 of movement or do you have to set it for .024-,030 of movement? A picture is worth a thousand words :) I plan on installing the collar and finishing my Taffy jetting next weekend. How have your results been?


yes, had to change jetting.as a matter of fact it was a pain in butt to get carb dial in with p38.but now that it is i must say it was worth it.current jetting at sea level 185mj,48pj,dvp needle 4th clip,pilotscrew 2 1//4 out. bill,try $80ishh

[ May 20, 2002: Message edited by: freestyle111 ]

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