CRF100F jetting help
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    Kiwi
    Posts: 363
    Joined: Thu Sep 25, 2008 12:22 pm

    CRF100F jetting help

    by Kiwi » Thu Jul 18, 2013 9:28 am

    I looked through many past posts but found no definitive info on jetting for a CRF100F. Most stock bikes are jetted lean from the factory thus requiring a re-jet. Add to the mix that the 2007 CRF100F I just bought for my son has an FMF pipe/muffler ... and the engine will be even leaner. Thus, does anyone have any jetting advice?

    So far this is what I have learned.

    Stock main jet = 98 (99101-GHB-0980)
    Stock slow jet = 35 (99104-KN4-0350)
    Stock needle = non-adjustable clip height (16012-KSJ-A01)
    Stock air bleed = 1.5 turns out from seated (16016-KSJ-A01)

    Internet research shows that others are running:

    Main jet = 102 to 115 (that's a pretty wide range!)
    Slow jet = 37 to 40 (again, that's a fairly wide range)
    Needle = no info on a different (better) needle
    Air bleed = some say to go 2.5 turns out

    Thus, if I average all the numbers it would indicate a ballpark setup of:

    Main jet = around 108 (99101-GHB-1080)
    Slow jet = around 38 (99103-KA9-0380)
    Air bleed = around 1.75-2 turns out (16016-KN4-L10; adjustable screw from 2004 CRF100F)

    However, does anyone have any more tried and true jetting info to offer ... especially for a CRF100F with aftermarket exhaust?
    2007 CRF450X with modified airbox, Uni filter w/no backfire screen, NCVS needle on 4th, 172 main, CRFs fuel screw at 2, Boyesen QS3, stock smog, 450R cam, FMF Megabomb header, Pro Circuit T-4 muffler, Pro Taper Evo bars, AS suspension
  • User avatar
    Kiwi
    Posts: 363
    Joined: Thu Sep 25, 2008 12:22 pm

    by Kiwi » Fri Jul 26, 2013 12:24 pm

    Based on the total lack of response to my original post, I went ahead and installed the carb parts that ball-parked on size/model/etc. which are:

    Main jet = stock 98 was replaced with a 108 (99101-GHB-1080)
    Slow jet = stock 35 was replaced with a 38 (99103-KA9-0380)
    Air bleed = stock non-adjustable air bleed was replaced with an adjustable air bleed (16016-KN4-L10) from a 2004 CRF100F and then set to 1.75 turns out

    The result is ... [insert drum roll here] ... the bike runs great! It not only has much better power, but gone are the jinky throttle tip-in issues and off-throttle pops out the exhaust.
    2007 CRF450X with modified airbox, Uni filter w/no backfire screen, NCVS needle on 4th, 172 main, CRFs fuel screw at 2, Boyesen QS3, stock smog, 450R cam, FMF Megabomb header, Pro Circuit T-4 muffler, Pro Taper Evo bars, AS suspension
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    crfsonly
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    by crfsonly » Mon Jul 29, 2013 5:37 pm

    excellent follow up! anyone else running this set up?
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  • Garandman
    Posts: 1
    Joined: Sun Jul 06, 2014 2:36 am

    by Garandman » Sun Jul 06, 2014 3:13 am

    We have a stock 2008 and I am planning on these changes as the bike will not idle well with the choke off and we get the non uniform throttle response and popping as well.

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