Pilot circit jetting, help!!!!



2 replies to this topic
  • Phile

Posted September 25, 2002 - 07:53 AM

#1

The carb on the WR400 and Drz 400 kick is the same carb. I am rejetting my yellow pig and need your help. Specifically the pilot jet circuit is what needs attention on my bike. I know that if I keep the ratio correct between the pj and paj then many combinations will work. I also know that some are running as low as 35 pj / 65 paj and some as high as high as 40pj /100paj, with 38pj / 72paj being in the middle. I am going to start at the low point of 35pj / 65paj and go up from there. My motor is full Yoshi (cam, ignition, header, muffler, w/ opened up air box) and I ride at 2,000 – 5,000 feet. Also, have Taffy mod, EMM, and a 158 main.

Question - If the pilot circuit is low (35/65) what will the bike be doing? How will it idle? Will it over heat? Will it pop and backfire on decelleration? What characteristics will the bike exhibit? Will it be harder to start or easier? How will I know to go up to, let’s say 38pj / 70paj or 40/75? And if the ratios get high like 45/100 what will the bike be exhibiting as far as how will it be acting? Same questions above. My concern is that I will start testing, like the way it feels, and not know what to change next to make it even better. Thanks for your input!

[ September 25, 2002, 11:02 AM: Message edited by: Phile ]

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  • Phile

Posted October 03, 2002 - 03:45 PM

#2

Anyone? :)

  • Hick

Posted October 03, 2002 - 03:59 PM

#3

I think the best approach would be this:

Install whatever PAJ you think should work with the size pilot you are trying. Ride the bike and pay attention to lower throttle positions and how it runs. IMO it is fairly easy to determine the best pilot just by going on a few rides and trying different things. Just look for best low throttle, low to mid rpm response.

Then look for holes in your PAJ jetting. If the bike pops a bit during high rpm, low or no throttle (like decel-engine braking) then the PAJ is too large. Likewise if the bike surges at constant throttle, high rpm, like a simulated freeway commute (low throttle, mid to high rpms) it is too large. Too small and it won’t be as crisp.

As I understand it the PAJ’s affect on the pilot circuit is most pronounced at higher rpms. Once I’ve settled on a pilot size I’ve never gone back and changed that, even after changing the PAJ considerably, which I did when trying to jet my pal’s KTM when he changed exhausts.

Hope this helps.




 
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