Strange XR650R issue!?

I have an 03 XR650R that has been uncorked, has an open air box w/ a Unifilter and is running a edelbrock carb. I'm in Colorado and ride around 6000 to 10,000 ft. It's geared at 15/48.

The bike runs great at all speeds and rpms except for at top speed. Once the bike hits about 85mph it cuts out, almost as if the cdi is cutting out or I am running out of gas. I should be getting at least 90/100 mph out of it. If I roll off the throttle a few mph then everything goes back to normal.

Any ideas?

Thanks Dan

Sounds like you might have the usual edelbrock topend tuning issues, if you tune this carb to be spot on midrange and off idle,this will result in being very rich up top and no topend power. That's why I went back to stock.

Did you ever get it to 100mph with the eddy? Mine with the eddy would hit about 96(gps), but again was pretty weak on top compared to stock.

I also have that problem on my 650l! I have pulled the plug and noticed it is running rich. I am running the 16 needle. I am going to drop to the 15 needle and give it lots of clicks on the adjuster. Hopefully this tunes it correctly. I am at sea level.

I have the same setup, and the same problem. I've posted about it here and tried different carb settings, but nothing helped. Somewhere in the low '90s my bike starts sputtering like it's running out of gas. Runs fine with no issues otherwise.

Are you guys running the right needle for the elevation? I have the Quicksilver on my 650R and haven't ever had a top end related issue and normally ride from 7000 feet up. Have hit 100+ with it.

My suggestion is to get your information together (needle taper, how many clicks in from full rich, etc) and call Rob Barnum and see if he can help out with your carb. He's the guy that set mine up when I was in Cali last year.

Whats your base set up?

Whats your base set up?

I don't remember what taper needle I have, but I'll check it later today if I get it running for you on how many clicks in from full rich I am.

I ran into the same thing at 8000 feet in Kennedy Meadows, CA on my uncorked stock bike. The bike has a B53E Needle (3rd Clip), 172 Main, 68s Pilot. It was running rich all day and I think I should have gone down to a 168 main.

I got the exact same cut-out on the top end but also had the delayed response bottom end. It was running rich everywhere.


I'm currently running the 17E needle @ 14 clicks. I staretd @ 10 clicks and it did the same thing so I leaned it out an other 4 clicks. I'm afraid of going too lean and running too hot. Right now the plug looks good.

I think Barnum recommends 17E @ 8-12 clicks for 8000 feet.

Up here at altitude a needle with the least amount of taper and a thicker tip would be ideal if I understand this carb right.

At full throttle the needle is the only thing that determines fuel. So to lean out the top end, you must drop needle size.

Wouldn't the engine need more fuel at top speed rather than less.

Seems to me that to go faster the bike would need to suck in more air and more fuel?

I had my bike rebuilt by Rob last November ---Eddie, 680 motor....II cam , and the eddie is tuned perfect, call him, he is good and is willing to help.The eddie adjusts w/ the red knob on the top, I have to toy w/ it when I go from sea level to High Dez, due to popping, the top end is fine.........

I have the biggest needle in mine...650R, and I have pulled 98.5 mph and never had any cutting out! nor w/ the stock when I was still running it... I am at near sea level, I am sure its not enough elevation to make a difference. I also ride the Hatfield McCoy trails, and never make any changes to my carb setting to ride there... not sure what the elevation is there!

Are you sure your not just banging the rev limiter???:thumbsup:

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