please help

[ironman250x]

I have a nearly stock 1992 250x and I just decided to get a little more out of it so I got an HMF Sport Series slip-on and a White Brothers head pipe. I reallized a backfiring on decelleration and the stock main jet is Keihen 122 so I ordered a Keihen jet kit with sizes 120, 122, 125, 128, and 130. First we put in the 125 and tried it out. It idled well but it still backfired on decelleration. So I stuck the 128 in and I realized a problem when I started it up. It was idleing at full rev and the head pipe was glowing red. So I stuck in the 130 jet and started it up. It then idled fine again but it was still backfiring on decelleration.

Please tell what I can do to fix this problem and if you can tell me what jet size I should be running for this set-up.

[Moto250X_Rider]

i have just about the same setup on my 250X....the 130 should do it ....u might want to clean your carb good

[Moto250X_Rider]

oh yeah did u take your carb off all the way when u put on the jets on?......if so u might have snagged your throttle like somewhere and thats why it was running at full when u started it
i'v done that already if it does it again put on the trottle cable a bit to free it up...just thaught of that....lol

[GPracer2500]

You'll need to adjust your pilot circuit to cure the pop on decel. The main jet has little to no affect when the throttle is closed.

http://www.exriders.com/vbb/showthread.php?s=&threadid=229923

[ironman250x]

I got a 132 main jet and stuck it in and it worked perfectly, no BACKFIRING and NO High rev idle. It runs like a brand new machine again.