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need to know asap
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Posted by: exrider12

i need help jetting my bike

mods
hmf full system
uni airfilter

elevation
1000-1200ft

symptoms
blue header
backfiring on decel

it has a dynojet kit in it with a 96 main with the needle and e clip and stuff like that

Posted by: mx825

check the FAQ.

96 main is way lean.

Posted by: tedwilley

96 is near stock. I have the HMF full system with a K&N, outerwear, Dynojet kit and no airbox lid at about your elevation.
I'm running 112 main with the needle clip on the third slot, and the mixture screw out 2 1/2 turns, with great results so far.
BTW all stainless exhausts discolor with heat.
The only definitive way (without an exhaust gas analyzer) to know whether your air to fuel mixture is correct is to 'read' the plug. Search on reading spark plugs for instructions.
But, a good rule of thumb is to go up or down one size until your backfiring stops on decel. Just don't start at 96!
Start with the recommendations in the FAQ for your setup, then experiment. After the first time changing your jets, it becomes a ten minute procedure you can do anywhere.

Posted by: exrider12

so should i go with a 102 or 105.did you use the instructions in the dynojet kit?

Posted by: tedwilley

Well, from my setup results I would start with the 105. And yes, if you have the instructions from Dynojet they are pretty good for starters.
If you start with larger than you think you will need, the only bad result will bogging and eventually missing from a fouled plug. This could take awhile to happen if you are close to the right size. If you are paying attention you can go down a size or two and try it again. A lightly fouled plug from being too rich will generally clear up rather quickly with some riding .
Same goes for too lean; PAY attention and correct your jetting right away and you won't have any real problems. Go too rich for too long and you will need a new plug (and you won't be able to ride for very long with a really fouled plug). Go too lean for too long and you could overheat, burn an exhaust valve or both.
Just be diligent about changing the jetting until you get the right results!

Posted by: ryanh250ex

OK i don't like to use dynojet but here goes

try a 105 or 108 main, e-clip in the 4th slot, 38 pilot, and screw 2.5 turns out.

Posted by: exrider12

105 is to big i was think 100-102.mine also comes with a size 42 pilot jet (06). im also gonna play with the screw a lil bit to get rid of the popping

Posted by: tedwilley

The fuel mixture screw only adjust the mixture to the idle jet. The idle jet rarely needs to be changed without major engine mods.
The most likely causes of you running lean is the main (popping after a full WOT run) and the needle (popping on almost all decelerations). The needle controls fuel from 1/4 to 3/4 throttle, the main from 3/4 to WOT.
Unless you are at a higher elevation than you indicated, I believe you will find that the 102 main will still be too lean.
The HMF full system moves a LOT more exhaust gas out and fresh air in than the stock exhaust.
I am running my main at 108, needle at three, from 150 to 3000 feet and it still occasionally pops on decel at the lower elevation.
With a 112 main, needle at four, it ran great all the time.
BTW, I went down in size to troubleshoot a problem with a Rev Box and am going back to 112 if Big Gun cannot fix the issue.