XR650L Performance

Just purchased a 02 650 that has already had some mods. They include XR Only exhaust, gear change, smog block off and K-N air filter. When the air filter was installed they cut out part of the air box on the right side and part of the left cover. The bike runs great at high RPM's however at low speed the bike wants to lurch. I was thinking of adding duct tape over the holes added however it's raining today and expected to do so for a couple of days. I just joined the forum and wanted to run the issue by some experienced XR members. I can send photo's if needed. I also read the up-grade on drilling the carb and would do so if that would solve the issue.

Thanks in advance...

Not sure what you mean by lurch. The L has a lot of low end so when you hit the throttle, it def wants to jump or bring the front up. Mine does in the first 2 gears.

Personally, the KN is not the best real dirt bike filter, lets a lot of crap in. I'd go UNI.

If I assume you mean surge instead of lurch, then I'd say you need to verify the state of your carb. Did the guy rejet, dif needle? shim the needle, drill the slide, what did he do?

Is the XR's exhaust a slip on or full system? I did a Trapp but also removed the header and opend it up some. I gained almost .1" on each headpipe by removing weld flash.

Otherwise, mine runs perfect. No backfire, no surge, no hunting. If you can still talk to the guy, see what he did to the carb.

I just purchased the bike this weekend and the guy I purchased the bike from did not do the up-grades. We said that he purchased the bike at 1400 miles. The bike has 3300 miles at this point. I ask about the jetting and he only knew that he was told it was completed. The exhaust is a slip on system. I've read about a up-grade of cutting the air box on the R version. The bike has this mod and I'm not sure it needs it? I'm going to try cover the added holes and see how it performs. The lurching and or surging is, when the bike is operating at low speed only. If you roll on hard it seems ok however when taking off it appears to stumble with low speed. I will look at grinding the inside of the pipe this winter or a rainy weekend. Is there any adjustment to make on the out side of the carb to try without removing the carb.

If you roll on hard it seems ok however when taking off it appears to stumble with low speed.

Mine does this a little. I am convinced that it is lean at low speed. I have the WB E-series pipe on a stainless fat tube header without steps. I am not sure who made the fat tube header, but it has no provisions for a heat shield. The snorkel is also gone and it has a K&N filter.

I am pretty sure the carb mods will cure the "bog" or "stumble" in my case. :D

Sounds like you need to take the carb apart and baseline it with the std mods.

There is a nice writeup on this site regarding the drill, shim, and jet recommendations. I only had to redo the main on my bike once to get it spot on. Oddly enough I didn't have to go up much on the main. But once dialed in you will not get the surging or hunting. I think I went to sudco.com for all my jets. I got a couple of the short pilots and several mains. I'm running a 155 main I believe and a 52 or 55 pilot, don't remember for sure.

covering the airbox up is not the answer to your problem. You will just be putting a restriction back in to bring your lean mixture back to closer to optimum.

Thanks for the help! Sounds as if I'm going to remove the carb and see whats been done. I did see the write up on the carb up-grade that calls for drilling. I was thinking of adding a larger tank and this would be a good time to make the change. Looking forward to riding this new beast. I've been riding street bikes for the past 20 years and felt like a kid again last night riding this Big Red Machine! My girls both have small XR's and now Dad has a matching bike. Looking forward to the family fun!

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