Factory R&D P-38 Question

6 replies to this topic
  • rvanliere

Posted July 04, 2002 - 06:40 PM


I recently installed the Factory R&D P-38 Lighting assembly to my 01 YZ426F . I have stock jetting and a Thunder Alley pipe . I was out testing it out today and it seems as if I blip the throttle that it about kills the engine . I have to roll on the throttle slower . wasnt this mod supposed to improve my bottom end . I have no idea if I'm running the right jets . How does a guy know . I dont foul plugs . It rarely pops on deceleration . I know , I Know ( I should have done the BK Mod . Well I already had bought this thing From a Guy on E-Bay . So It should do what it claims right . Please anyone with experience on these things let me know what I am doing wrong . Besides spending $70 on a bolt on piece of junk. :D :D :D :D :) :D :D

  • Hick

Posted July 04, 2002 - 09:39 PM


Sometimes the accelerator pump can gloss over jetting problems at lower throttle positions. In theory, anyway, you should jet your bike at static (fixed, unchanging) throttle positions, which would mean the pump is off and not affecting things.

So what may be happening here is when you limit the pump via the P38 you are unmasking a lean spot as you go from pilot to needle.

If you were happy with how the bike ran before you could just remove the P38, but if you were then why would you buy the P38 to begin with?

First things first, if you are that interested in getting the most out of your bike you need to experiment/fine-tune the jetting first, and worry about your accelerator pump later. I actually disconnected the pump on my ’00 and rejetted the bike. It makes a huge difference.

Hope this helps.

  • themotoxguy

Posted July 05, 2002 - 01:19 AM


i have p-38 and it works great.you just have to play with jetting

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  • Guest_blatham489_*

Posted July 05, 2002 - 05:23 AM


Good luck regardless, but I did get a chuckle out of "it should do what it claims, right??"

  • Shawn_Mc

Posted July 05, 2002 - 08:13 AM


Make sure the accel. pump is functioning, then you may want to go up a size on the pilot and raise the needle in the carb one or two postions. Better yet, put that thing on ebay, and do the Bk mod for 13 cents.

  • Boit

Posted July 05, 2002 - 10:40 PM


My '00 had that damn annoying hesitation. I installed the P-38 and delayed the accelerator pump timing by 1/4 turn on the timing screw. What an incredible cure! By the way, this was before the BK mod was developed. You might get great results if you are willing to play around with the carb. Jetting might be the answer. Adjusting the timing screw might also be the answer. If you decide to adjust the timing screw, just make damn sure you know where you started so that you can go back to the original setting. I would try 1/4 turn increments and then test for at least 30 minutes. Good luck.

  • Cobra314

Posted July 06, 2002 - 07:53 AM


Like the motoxguy said...you just have to play with the jetting. I had a hell of a time getting mine right, but when I did it freakin rips!!

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