jetting settup for mountains

5 replies to this topic
  • uw153

Posted May 12, 2003 - 03:28 AM


Good morning all, I am heading to the Missoula MT area in July, I think the mountains around there are in the 7-8000 ft range. I am from Iowa where of course I'm much lower. My question is I have me XR setup with the snorkel removed, K&N filter, 160 main, with needle in third position "K&N", using the stock pipe. Doesn't run perfect here but I would like to know what I may need to do up in MT? I am taking both my DR 650, and the XR650 so I figure I'll have to do the same to the suzuki. Looking forward to some sweet mountain riding in the Lolo area. For those of you in that area any suggestions??

  • AzMtnThumper

Posted May 16, 2003 - 03:50 AM


I ride at 6,000-8,000 feet most of the time in the summer. With the jetting I run at this elevation the bike will run OK down to about 4,500 - 5,000 or so feet before it gets to lean (popping on deceleration etc). I have been able to get by most of the time by just swapping the main and readjusting the idle mixture (easy enough to do on the trial). So I would suggest maybe getting two main jets leaner and maybe have a pilot that is one size leaner (I would lean it out a little at a time though). That should get you in the ballpark.

  • uw153

Posted May 16, 2003 - 07:06 AM


Right now I'm in Iowa which I think is 200-300ft above sea level. I am running a 160 main right now. What jet size do you recomend I take with me?

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  • smashinz2002

Posted May 16, 2003 - 07:34 PM


From 6,000' to 8,000' use the following jetting setup. I have done it and works well without overheating at low speeds on mountain trails and 4x4 roads in Colorado:
160main, needle in 3rd clip position, stock pilot. If you ride above 9,000 for extended periods consider a 155main, with other settings the same.
Please keep in mind these jetting changes are NOT for the stock intake and exhaust!! Intake should be 40mm boot, airbox baffle plate AND snorkel removed, and running either the 40mm exhaust tip OR the modified stock tip at 34mm or 36mm (drill-out mods).
DO NOT run the stock intake system and stock exhaust tip with the above jetting which I mentioned.
Jetted as mentioned, with the correct intake and exhaust tip changes, will result in fair power output and fairly easy starting, with no low speed overheating, at altitudes above 6,000'. Sputtering will occur with this setup above 10,000', which can be helped somewhat using the 155main if you are planning on riding that altitude for long periods. Whatever the case, be aware that no jetting changes will make the bike run as well in high altitude as it will in low altitude such as Iowa with a 175main and above intake and exhaust mods. Hope this helps!
I'm editing this for one last thought for you. In Iowa, the altitude is low enough that you should certainly be using the 175main jet, 40mm intake boot, 40mm exhaust tip, and airbox baffle plate and snorkel removed. I just noticed the setup you mentioned. That is incorrect. The bike with the stock exhaust tip is overly restricted and intended only for the stock jetting/intake system. Mis-matching intake/jetting/exhaust mods will not make the bike run as intended by the Honda engineers. Mod must be done correctly and all as one unit. Honda designed this bike to be widely tunable for power output, riding situations (such as dual sport, off-road, or all out racing), noise levels, and off-road legality depending on location. The XR650R is the most tunable bike for differing situations that I have ever seen. However, mechanical knowledge is necessary to tune it to your specific needs. If you have any questions at all concerning the bike, power output requirements, noise level requirements, or otherwise, please email me for information on this topic. It seems like the only mistake Honda makes is assuming that the general population will know how to properly tune the bike for any specific use that is required by the rider. I could get into depth on this topic, but space does not allow. Basically, it sounds like your bike is "mis-matched" on the intake/jetting/exhaust issue. Just run the 40mm intake/40mm exhaust/ 160main/ stock pilot/ airbox baffle plate and snorkel removed.. and you will like it in the mountains!! When you get back to Iowa, change the main jet to 175 and enjoy!

  • uw153

Posted May 18, 2003 - 04:40 PM


I think your talking about the 650R. I have the L. Would like to have an "R" model but for now I'd better stay with the ole air cooled dinosour. I don't believe I can get any different intake boots or exhaust inserts for the "L". I'f I'm wrong please let me know I sure would like to do more to this ole girl.

  • smashinz2002

Posted May 18, 2003 - 06:05 PM


Ah man I'm sorry about that, didn't notice you had the "L" model. My mistake. I wish I could help with the "L", but I'm not familiar with it. See if your owner's manual has a jetting chart maybe? I know the manual for the "R" model has a jetting chart, so who knows. Sorry I mistook your bike for the 650R!
'00 650R, powered-up, dual sport kit, and a "fear this" sticker, haha
'98 CR500R, completely stock and fun to scare yourself.
P.S. If you ever do get a 650R, and install the power-up kit, get ready for a wild ride! The bike is scary fast like a CR500, but the power is much easier to control. However, wicking it open will no doubt have you hanging onto your shorts, and most likely you will be shouting "holy sh**" at the same time. hahaha. Enjoy!

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