High altitude jetting for 650R?

I'll be doing a ride from Denver to Telluride CO. in a few months. We should top 12,000 ft. altitude so will need significant changes from sea level jetting. Any Colorado residents who can share their jetting specs for an uncorked but otherwise stock 650R?

Last year I rode from 9,500 to 12,000 ft. I changed from a 68s pilot jet to the original 65. I put the factory needle/seat back in and lowered it one clip position (2nd slot from top). I changed the main jet from a 175 to 160. My pilot adjustment screw was stuck and couldn't be adjusted so I never got it to run really clean on bottom but it ran clean from 1/4 throttle to wide open. I was using the factory exhaust tip drilled out to 2". No holes in side cover. I couldn't get the bike started with the low altitude jetting. There is a substantial loss in power at high altitude.

I'll be back up there in 2 weeks with 2 XR650R's. I purchased an Edelbrock QS the day after I got back last year just so I wouldn't have to rejet. I will prepare my spare carb to put on the other bike for when we get there. It will be jetted as above.

hey, a few months? that would be late october, you may need a snomobile at 12k feet. i have a 650r with a drilled airbox and i left the cork in (i dont like the sound). i live at 10k in Leadville and ride mostly above that, you should be fine if you just bring down the main into the mid 160's maybe even 160, you can change the pilot and the clip but it's a pain in the ass and you'll never get the low bog out of it anyway. the common mistake is to lean the pilot circuit at altitude, you have to richen the pilot circuit because the air density is low and off the bottom you wont get enough fuel because of the lack of air sucking it into the system. keep in mind it will be cold by then and the whole thing will run leaner anyway. if you're running roads mostly then change the main and have fun, if your gonna do some tight trees and single track it may be worth it to move the pilot up to a 72 or 75. Denver to Telluride sounds like a blast, whats your route? how long will you be out? if you make it near Leadville stop by for a beer. have fun!!

Just got back from Colorado and rode from 8,500 to near 13,000 ft. One bike had stock carb with 2" hole saw modified spark arrestor, no holes in side cover. This bike normally runs a 68s pilot, B53E needle and seat and 175 main jet at 900 ft. altitude. I setup my spare carb with 65s pilot jet (stock), B53F (stock) needle and seat on 2nd clip position from top, 160 main jet, fuel screw was 1-1/2 turns outs. This bike ran very good jetted this way. The only problem it had was the float level was set a little bit low and it would leak gas when leaned over or on a steep incline. My bike was running an Edelbrock quicksilver with 2" hole saw modded spark arrestor with holes in the side cover. I ran this bike with the needle that came in it. I'm pretty sure its the 18e. It was adjusted from 12 clicks out to 16 clicks out. This was from fully screwed in clockwise and then backed out counterclockwise. This seemed to be backwards from what I would have envisioned lowering the needle would have been. This bike ran great as well. We rode one loop that covered 73 miles and we never went on reserve with stock tanks. Never checked the plugs but the exhaust tips looked like jetting was spot on. Temperatures ranged from 37 degrees to 80 degrees F.

That's good to know, thanks for the info. :D

I reside in Colorado and ride from 6,500 to around 10,000. My pilot is the stock 65s, the needle is stock in the stock position, the main was brought to a 160, and of course the bike is uncorked with the HRC tip. No real problems. At higher altitudes starting seems touchy at times.

Thanks for the great info. Averaging out what I read here and elsewhere, the stock 65 pilot works for everyone but the chart shown here http://www.xr650r.us/jetting/ says a 62 might better for 10000+ and a hot day. I might also do Pikes Peak to (14000+), so I'm installing a 65 but bringing a 62 with me. Hopefully just twiddling with the air screw with a 65 pilot will get me by?

The 160 main jet is a good compromise and I don't think its too critical. Except for a friendly drag race or two, we'll never be on the main jet. The charts suggest leaner yet for extreme altitudes and warm temps but a cool morning in Denver would need a 170. 160 looks like a good compromise and its Ok if it runs a little fat at 12k on a warm afternoon.

There's more choices with the needle. Stock B53F needle, second groove down seems to work fine for everyone. I also read somewhere else? that the B53E needle used for uncorking may be the better choice but would use a different groove? Its probably a subtle difference and I can't remember where I read about it? we may jet two bikes the same except for the needle and see who's runs best?

I'll be there in 3 weeks and hope the temps don't change much. 37-80 is quite a spread,.. add the possibility of rain and it makes it tricky deciding on riding gear. We need to carry gear for 4 days but will be using motels. I can't wait!!

The B53E is a richer taper. I'm not sure that even on the top notch it would be lean enough. I tried it the year before and it was on the 3rd notch and the bike would barely run it was so rich. When I tore it down to change it, I just put the original needle back in. I think the pilot adjustment on the stock carb is referred to as a fuel screw since it isn't on the air side.

The Edelbrock was sure nice to have. I thought that turning the adjuster clockwise would lean it out but after about 6 clicks in, it was so rich it would barely run and you could see gas in the exhaust. I have read where some people can adjust them without removing the tank. They must have little baby hands, because I sure can't. It was still an easy adjustment after going the right way. Also didn't have to turn the gas off at every stop on an incline like we did with the stock carb. It took 2 years but I can set them up before I leave next year and have them run perfect.

I feel sorry for the people that have to ride at this altitude all the time. They don't realize how much power they are missing on the BRP. Its hard to keep the front end up any length of time up there.

Your right, I'm all screwed up,.. its a fuel screw not an air screw. I'm now hearing the B53E is a different taper and richer at the tip? It comes with a matching orifice seat, did you switch that back to stock too? There may be some perfect "mix and match" combo of those parts but I'm feeling lazy and will just go back to stock needle and seat.

I had my CRF450 up there in the past and you're right about the power loss. A 250 would run like a moped in the thin air. I thought I had a turbo when I got home. Lots of funny stuff with the thin air, you get way better gas mileage, the bikes kick easier (low compression?) and they are quieter. Grocery stores are funny too, all the potato chip bags look like baloons ready to blow. I thought my head would explode too for a day or who.

I thought about rushing there a day early and riding up Pikes Peak but going from sea level to 14000+ft. that fast might be uncomfortable??

Any advice about a higher pressure radiator cap? some of us overheated on the last trip. Anyone know of part numbers from the auto parts store so I don't have to pay $33.00 from SRC?

The needle and seat are supposed to be changed as a set. I changed both. I don't run a higher pressure radiator cap as I don't want the additional strain on hoses and radiator. I use Evans coolant in both bikes. Its been in there for over 3 years now. I installed RTDs in the oil dipstick tube and monitored the oil temps when I first changed over. Neither bike ever got above 230 degrees F oil temp. I measured an air-cooled 1996 XR600R and it consistantly ran hotter. I was very skeptical of the Evans at first but it works and there is no pressure on the cooling system.

Texas beer sure gets foamy at high altitude :D

A lot of people are saying the new cap is a bad idea and it does make sense. I've never had cooling issues because I never sit and idle,.. just keep moving. I've used engine ice with good success and wouldn't mind trying Evans if I could find some before I leave.

Is there anything I could drink that would give me more red blood cells. Those altitude headaches are nasty.

Just stay hydrated on the way up not just water as it will flush out the electrolytes. I am rarely effected by the altitude but have friends that are. It sometimes takes them a couple of days to adjust. It can be a real problem for some people and is serious. Do some research and take the necessary precautions. Some people have to carry oxygen to cope. Yes even at 10,000 ft.

Most people don't take it seriously but I suffered with headaches for a few days the last time. I did some research and they say you should take a day for every 1000ft above 8000. The mountain climbers are a lot more aggressive but still careful. Pilots are required to wear oxygen above 10,000 but dirt bikers are allowed to slide around blind turns going up Pikes Peak at 14,000,... go figure?? :D

One itinerary would have taken me from seal level to 14000 (Pikes Peak) in less than 3 days but I decided to get there early and camp a few days around 8000ft. They say your body produces more red blood cells quickly. I like the water/electrolyte idea and I have some special juice for running that would be perfect. Gotta look for some portable oxygen now so I don't get like this :D

Doing a little research for my High altitude settings. Which needle and position are you running? and how many turns out is your air screw?



Stock needle in the stock position works very well for an uncorked 650R at alt. I'm at 6,500 and typically ride from there up to around 10,000.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now