Results 1 to 10 of 10

Thread: CRF Jetting and setup

  1. #1
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default CRF Jetting and setup

    Ok i nosed around with the search and didn't find what i was looking for.

    Took my CRF100F out to the track with GAMRA today, for my first trackday. What a blast. I did however find out that I need to do a bit of work. I encountered some oddball fueling.

    What I got was some really heavy stuttering on rapid throttle transitions. this was where it was most noticeable. Additionally I was getting some stutter at full throttle. Low rpm throttling is fine as long as I was rolling the throttle smoothly. Quick changes weren't rewarded.

    Bike starts up fine and warms quickly.

    I'm going to pull the carb and give it a good cleaning first and foremost. (along with a new plug and oil change)

    I'd like to get rid of the airbox and replace with a pod filter. I haven't been able to find any specifics regarding this.

    Anyone here ditch the airbox on a 100? What kind of jetting and pod filter did you use?

    Thanks!

    On another note, anyone know of a rear brake pedal that's longer. Or Perhaps I mean wider? I have to really turn my toe in to get to the rear brake...
    Last edited by ACDNate; 05-08-2010 at 05:14 PM.

  2. #2
    Join Date
    Aug 2005
    Location
    Concord,CA
    Posts
    1,254

    Default

    Bend the brake pedal out.
    • '08 Ducati Hypermotard 1100S
      '07 CRF150R Expert #888 SMUSA
      '06 CRF100F
    • '03 XR100R #888 SMUSA

  3. #3
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default

    Ha! The simplest answers always seem to allude me.

    Good call!

    Anything on the jetting???

  4. #4
    Join Date
    Aug 2005
    Location
    Concord,CA
    Posts
    1,254

    Default

    I run the stock airbox, but I have opened mine up. I removed the snorkel, cutout the top, drilled and installed the round filter vents on the front and side, and removed the backfire screen from the filter cage. I rejetted for the exhaust and bigbore kit to a 107.5 main and moved the clip down one notch. Maybe this will give you a base to start with. You might just take a day at the track to dial in your jetting. Just bring some main jets ranging from 102 to 110 and experiment. It is not that difficult.
    • '08 Ducati Hypermotard 1100S
      '07 CRF150R Expert #888 SMUSA
      '06 CRF100F
    • '03 XR100R #888 SMUSA

  5. #5
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default

    Any memory of what your stock jets were?

    I've searched here and thumpertalk and found differing opinions

  6. #6
    Join Date
    Aug 2005
    Location
    Concord,CA
    Posts
    1,254

    Default

    Stock is #98 main and #35 slow jet
    • '08 Ducati Hypermotard 1100S
      '07 CRF150R Expert #888 SMUSA
      '06 CRF100F
    • '03 XR100R #888 SMUSA

  7. #7
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default

    So I pulled apart the carb to give it a cleaning. This is what I found

    Factory settings as I have found searching other forums and from the factory service manual:

    35 Pilot
    98 Main
    3rd notch on the needle
    2 3/8 turns out on the pilot screw (add 1/2 turn for low altitude)

    What i actually had in the carb:

    38 Pilot
    98 Main
    5th notch on the needle
    3.5 turns out on the pilot screw

    The pilot and main jets were both clogged up pretty well. I cleared them and gave the whole carb a really good cleaning. It all went back together and started up with no drama.

    The issue I'm encountering is how to go about adjusting the pilot and idle. The manual states that the two should be set in sequence to each other. The manual states to use a tachometer and view the difference in idle speed while adjusting the pilot at a previously set idle.

    Is there any easy way to do this w/o a tach or do I just need to find one of those guys who can do it by ear?

    I set the idle to a range that sort of sounded right and gave it a ride around the neighborhood. It didn't stutter as much but still had something a bit odd going on.

  8. #8
    Join Date
    Aug 2005
    Location
    Concord,CA
    Posts
    1,254

    Default

    Try a test run with the airbox cover off. Make sure that you have a clean air filter. This can tell you if you are running too rich or lean. If it runs better without the cover, too rich.
    • '08 Ducati Hypermotard 1100S
      '07 CRF150R Expert #888 SMUSA
      '06 CRF100F
    • '03 XR100R #888 SMUSA

  9. #9
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default

    Fresh factory filter put in last wed...

  10. #10
    Join Date
    Aug 2009
    Location
    Gulfport, MS
    Posts
    330

    Default

    So I wandered into Harbor Frieght (conveinently located next door to my office) and found a Multimeter with inductive tachometer.

    http://www.harborfreight.com/3-1-2-h...kit-95670.html



    Taking a look at the manual the inductive tach feature has settings for 3, 4, 5, 6 and 8 cylinder engines, utilizing the black clamp (in the pic above) on the spark plug wire. As I understand inductive tach's they count the firing of the spark plug for measurement.

    Does anyone know if there is a logical method for using this on a single cylinder engine? Like dividing the readout by 4 when set on 4cylinder etc???

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •