High Altitude Jetting ????

2 replies to this topic
  • MtnDoo

Posted March 15, 2003 - 10:33 AM



I have a 2000 XR650r.
Can anyone suggest jetting specs for 8500-11,000 ft?



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  • smashinz2002

Posted March 15, 2003 - 07:31 PM


Hi. Yes, I can give you some tips on high altitude jetting above 8000ft. I have a place high up in Colorado, and have learned what works on the 650R from experience. So..If you are running stock, forget it, it can't be jetted right. The bike will always run too hot, especially at low speeds. Boil over will probably occur. Don't play around with higher pressure radiator caps to cure this, it's not a good idea, it places undue stress on the radiator hoses.
Install the Honda Power-Up kit, and install it correctly, including removing the airbox restrictors. Then; if you run the modified stock exhaust tip (34mm), then set the jet needle to 3rd position if you have the competition needle, or 4th position if you have the stock jet needle. I suggest getting the competition needle and setting it to the 3rd position. Now, install a 160 or 165 main jet. It will run fairly rich, but for slower high elev. tough trails or 4x4 roads, the richer setting will prevent overheating at the low up hill speeds. When I say low speeds, I mean anything lower than a steady 30mph. Also, the thin air does not cool as well. This is the reason so many people jet too lean, and then the bike boils over. I know from experience, I have done engineer's pass, as well as many other high passes in Colorado, and know these settings work for the 34mm exhaust tip.
If you are using the power-up kit and the 40mm tip (competition tip), you can also set your jet needle to 3rd position (competition needle), and use a 165 main jet, or 170 for below 5000ft. Don't worry, you won't foul the plug. If you are using aftermarket headers and silencer, then it depends on how restrictive the pipes are. Less restrictive=richer settings.
The main point to remember when jetting the bike, is that high performance 4-strokes require fairly rich settings in order to produce good power without overheating. Also, keep in mind that some people jet overly lean thinking that since they are going to go to 12,000ft, that they need very lean settings. However, they forget that the bottom of the trail will be much lower, and lean setting could cause a boil over. Hope this all helps out.
2000 XR650R, Power-Up Kit, Dual Sport Kit, speedo, lots of goodies.

  • Big_D

Posted March 17, 2003 - 07:21 AM


Hold on SMASH. Getting an XR650R to run like a scalded cat at altitude is NOT that hard. I LIVE in Denver and do ALL of my riding at 4800' (Pueblo in the winter) and UP.

Here is what I have done to my '01. Take the stock 49 state bike (no smog crap). Pull the airbox snorkle and block off plate. Open up the intake manafold (or by the power-up piece). Replace the stock exhaust tip with the HRC power-up tip. Now you have a bike that is "uncorked" without spending a grand on the full power-up kit (which does add even more power).

Details for this with part numbers are found at http://www.XR650R.net under "Making the XR650R run right (un-corking it)" on the left side.

Now to jet the beast. Let's start with the hot setup at Sea level with the mods above as a baseline. 175 Main Jet, Stock Needle with Clip in 3rd spot (Some people change the needle with the HRC) and 68S Pilot Jet. Now to correct these settings for about 7000' which is a good Mountian setting for Colorado especially if you are in the Denver area and ride Rampart Range. The correction factor would be about .91. This number is from the jetting chart in the Honda Service Manual. Using .91 the Main jet will be a 160 (175 x .91 = 159.25 fudging on the rich side is 160) The manual also states that if the correction factor is below .95 that you should RAISE the needle one position. So when the sea level guys drop the clip one spot and we raise it back up, so you can leave the needle alone. I also left the leaner 65 pilot jet in my bike which works just fine.

So after a long explination I would just pull the restrictors from the airbox, get rid of the intake manafold restrictor, open up the exhaust with either a hole saw or a HRC tip, and swap the main jet for a 160 or so. The only other thing that I had to do was play with the air bleed screw to get the bike to come off idle better. My setting is 2 1/4 turns out.

You can make a stock bike run great in Colorado for about $10. $5 for a main jet, and $5 more for a cheap hole saw.

Hope this helps!

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