Results 1 to 2 of 2

Thread: Jetting Carbs Redux (1998 YZF750R)

  1. #1
    Member BushyAR15's Avatar
    Join Date
    Mar 2011
    Location
    S/E Aurora
    Posts
    307

    Jetting Carbs Redux (1998 YZF750R)

    The continuing saga of restoring my '98 YZF750R...

    Did a search on this forum and saw/read some helpful information. I initially thought it might be an overly rich condition, but reading through some of those posts it sounds like the carbs can be tuned too lean on the bottom to too rich on top so it needs an entire tune.

    The bike is running pretty good. However, the carbs need to be rejetted (tuned) due to our altitude. What I notice is if the bike idles for a long period of time the carbs load up. So taking off from a light the bike is very slow to move until the carbs clear up. Seems holding the throttle at 1/4 throttle open and above it runs fine. Seems to only be an issue of loading up when idling. If I roll on the throttle after it is has cleared the loading up meaning quick and steady roll on to WFO, it runs pretty good.

    So what I'd like to do get rid of that initial bog.

    Its been years since I worked on carbs and I've forgotten some of it. I'm thinking it might be the pilots and/or the air screw mixtures? Not the mains or the needles since it seems to go well when rolling on the throttle?

    Wondering if I should pick up a dynojet stage 1-3 kit and fit that... But I remember playing with those, they usually have you drill out things, replace the main jets, replace the needles, on and on. I guess I'm wondering if I should get the Dynojet kit but concerned its just going to cause more work issues, than trying to figure out the low-end/idle bog...

    Thoughts?
    2016 Honda Africa Twin
    2015 Ducati Monster 1200s Stripe
    And Freakin' Old

  2. #2
    Senior Member TFOGGuys's Avatar
    Join Date
    Jan 2003
    Location
    What am I doing in this handbasket?
    Posts
    3,838

    Re: Jetting Carbs Redux (1998 YZF750R)

    Float level needs to be set precisely on those particular carbs. You also need to look closely at the needle jets, as they have a horrible reputation for ovaling out, sometimes as low as 10K miles. They're about 13 bucks each from Yamaha.
    Thanks, Jim
    TFOG Wheelsports, LLC
    www.tfogracing.com
    303-216-2400

    Calling an illegal alien an "undocumented immigrant" is like calling a drug dealer an "undocumented pharmacist"



Similar Threads

  1. Someone to sync my carbs
    By B_Ott in forum Bike Tech
    Replies: 5
    Last Post: Thu Jun 25th, 2009, 05:07 PM
  2. Tuning/Jetting a 1998 R1
    By Repsol a095 in forum Bike Tech
    Replies: 10
    Last Post: Wed Mar 28th, 2007, 07:53 PM
  3. Carbs, Jet Kit and A/F Mixture Help
    By JustSomeDude in forum Bike Tech
    Replies: 8
    Last Post: Wed Mar 14th, 2007, 11:20 PM
  4. EX 500 running like crap....Redux
    By vw143 in forum Bike Tech
    Replies: 8
    Last Post: Sun Mar 20th, 2005, 08:57 AM

Posting Permissions

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