Jump to content
Sign in to follow this  

Jetting and/or Rev Limiter???

Recommended Posts

I thought I had a handle on jetting but the more I try the more I realize I don't know. I have been reading and searching this forum and the jetting forum. I have read almost all the jetting data base in this forum and still not having any luck sorting out my bike. I have a couple of problems. First, when at 3/4 to full throttle in lower gears (possibly higher gears also, don't have a long enough run to tell) my bike starts cutting out. It acts like a the rev limiter is kicking in, but I really don't know. I wouldn't think that it would happen at 3/4 throttle. I did run the bike up to the rev limiter while coasting to see if the sound was similar, it was. I have been careful while reassembling the carb trying to make sure there are no vacuum leaks. Currently have a 165 main jet and a plug reading looks as if it is lean. Does hitting the rev limiter cause a lean condition? Does anyone use a larger main jet than a 165?

Also, I have the off idle bog when I gag the throttle. It seems to have gotten slightly worse as I richen jetting trying to get rid of the high rpm cut out.

This is my current jetting along with what I have tried. This is a 2001 kicker model.

Altitude 500 ft. Aproximately 70 deg. F. stock air filter, Bel-Ray oiled.

165 Main Jet (Have used a 160 also)

200 Main Air Jet

JD Blue needle 4th clip from top (Have used the 3rd clip also)

38 Pilot Jet

72 Pilot Air Jet (Have used a 70 also)

2 Turns out on the Idle mixture screw (Have been from 2 1/2 to 1)

Coast Enrichner Removed

My version of the taffy mod (Cut the ap pump stroke >50%)

The bog is always there when the throttle is gagged. When riding in the woods, using proper gears, aggresive throttle control, and in the meat of the powerband, these troubles don't appear. But I do some riding in the flats where wide open throttle is a must. It is just the extremes that are giving me problems and just feel that these problems are correctable.

Thanks for any help. I may not be able to respond to any follow up question immediately do to having to go to work.

Share this post

Link to post
Share on other sites

No doubt you are into the rev limiter. If you want to know for sure, use a speedometer and calculate engine speed from the gear ratios vs the indicated speed. I would suggest a 158 main jet. No way to cure hitting the rev limiter - shift. Snapping the throttle open at too low an engine speed is something a carb is not designed to do. If it works good riding, it is good. That is the only way to evaluate.

Share this post

Link to post
Share on other sites

Thanks Noble, I will have to get a car to run besides me for the speed. I also forgot to state that I have the intake restriction off the airbox with an extra 1 1/2 inch hole drilled. Along with a FMF Q2 / Powerbomb exhaust.

Share this post

Link to post
Share on other sites

You can hit the rev limiter at 3/4 throttle no problem. I'm almost positive that's what it is.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

  • Similar Content

    • By Bignerd0100100
      Hey all, 
      I'm looking at buying a 2004 Suzuki DRZ400EK or at least I think it's an EK according to Vin lookup websites, but it does not appear to have a kickstarter. I was told the bike was owned by a motorcycle dealer and that it has a current green sticker, and a California license plate but has not been registered for the streets since 2011. I want this as a dual sport but am not clear if the fact that it already has a plate means I am good to register it or if maybe they took away the ability to register it after it was plated, California loves to do that kind of stuff. Since the bike was owned by a dealer I would think they were up on the latest regulations in California, but who knows. Can anyone add any insight as to what I should look for on the bike itself like the carburetor, model numbers etc? Or do I just try my luck at the DMV?
    • By smokey9lives
      I have a 2003 DRZ (actually a KLX400) and the head tube bearings are shot.  I ordered a new set to install but I'm wondering if anyone has any recommendations on other parts I should replace while I have the front disassembled.  I was thinking about new rubber fork protectors, but are there other things that wear out on the DRZ front ends that you can only get to when disassambled?
      I also broke off a replacement key that I got for the steering lock.  I must have been made of cheap pot-metal.  Should I just remove the whole lock mechanism?
      Any tips or tricks for getting the old bearings out and the new ones in would be welcome!
    • By antonyp
      Hey Guys,
      I recently bought a 2003 DRZ400S and thought it would be a good idea to check the valves clearance etc . I timed the engine on TDC with the magneto mark aligned as per the manual but I find the cam timing slightly odd. The arrows pointing upward are on the 1st and 15th pin as they should but with the magneto timing mark aligned they are not perfectly straight. Same goes for the arrows that should be parallel to the cylinder head casing. Is this normal or should they be absolutely perfect ?