650L carb modification jetting info

5 replies to this topic
  • dabeyta3

Posted April 28, 2005 - 01:49 AM


I have been observing many people who are doing the Carb mods by Dave. I did them and they really work well. But I think many people are over jetting the bikes. I see some people are putting in 165 main and 62 pilots, with very few intake/exhaust mods. I am almost at sea level (1000)FT and have a full White Brothers exhaust, K&N filter, and de-smog done on my bike. I run a 160 main and a 55 pilot. I started richer a 160 main and a 58 pilot and the bike wouldn't idle to well, smoked, and needed gas to start. Everyone told me the bike was to lean. So I enriched the mixture screw, and there was no change. Upset, I decided to walk away and eat dinner. After dinner I thought maybe it could be to rich. So I turned in the mixture screw almost all the way to lean it way out and the idle changed for the better, and less smoke. So that told me it was to rich. Went and bought a 158 main and 55 pilot. All problems solved immediately. Rode the bike for a while, checked the plug and some white was visible. Put 160 main back in and now it's golden brown. The bike idles perfect, more power, and starts perfect. My main concern is that a lot of people see "rich" signs as being to lean. A lean pilot will cause the engine to die after hard gassing. A lean main will cause the bike to overheat. A rich pilot will cause a bad idle, gradual shut down and hard warm starting (BETTER COLD STARTING). Always after doing any re jetting CHECK THE PLUG. A white plug means to much heat (to lean), while a black plug means to rich. Golden brown is what you want. And last but not least the mixture screw should be between 2 and 2 1/2 turns out. The jets are 99% of the mixture. After finding the right spot, the mixture screw should only be used when riding at different elevations. If going up lean out, and going down richen up. Adding a pipe, richen up etc.....Please give me opinions if you agree on the overjetting problem I speak of.

  • ghoti

Posted April 28, 2005 - 02:50 AM


If I recall Dave's formula is 158/55. I happen to run 160/55 do here in muggy Texas. I had some high speed knock that this seemed to help. A note on plug color, if you do a lot of high speed droning, i.e. freeway riding, the plugmay still appear lean. The manual even recommends going one plug colder. If I were to err, it would be on the rich side.

  • thumper447

Posted April 28, 2005 - 04:46 PM


What does Dave say about the jetting on the 650r?

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  • zooboy

Posted April 28, 2005 - 05:19 PM


I am waiting for the new jets from Baja Designs 158/55. I will post when completed. I do not know about the 650R, as I am pretty sure it is a totally diff carb. Keep searching this site I am sure you will find what you need, or just make a post and ask.


  • XR650L_Dave

Posted April 28, 2005 - 06:25 PM


Yeah, R is whole different critter.


  • XR Dude

Posted April 29, 2005 - 05:31 AM


I totally agree, one thing I've noticed though is some people get confused between the dynojet #'s and the keihen #'s. For instance a 160 main keihen is not the same size as a 160 dynojet. I see some crossover on the posts as one person recommending a certain jet size and not identifying the company so the other person gets the opposite companies jet and is confused, then its Dave or someone else to the rescue to explain it, which is the great thing about this site. Just my .02. Ride on my friends.

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