97 XR650l not quite running right

I was hoping someone can help me. I hang out mostly on the XR250 board but have just bought a XR650l and am having some problems with it. I haven't gotten to tear into her yet so I have somewhat limited information but figured I would post anyway and maybe someone would be bored and could help me out. First here are the mods to it emissions crap gone, Wiseco piston kit, Mikuni flatslide pumper carb, XR's Only stage1 cam, a K&N pod filter, and a WB E2 exhaust. Now here is the problems. It pops on decel which I am guessing is b/c I am lean but the real thing is that it is hard to start and stay running. After it is pretty warmed up and I take off it dies when I pull in the clutch for a stop. It is pretty frustrating. Also sometimes at idle it makes a gasping sound and then dies and the whole time it is idling it just doesn't feel smooth, if that makes sense. I am guessing that when I rip into the carb and look at the jetting it might help but I was wondering if anyone else had any ideas.


Check valve lash.

should it be 4 and 5 thou even with the stage 1 cam?

Dunno about the lash adjustment with stage I cam? Someone here can tell you that has one installed.

Check for vacuum leaks....Valve lash..carb jetting...Spark plug OK...


Can someone explain the operation of a pumper carb. the only hose that i have on it is the big fuel hose, am I suppossed to have anything else on there. Also the brass looking screw on the side, is that for idle or something else. If it is not then where is the idle screw located. Thanks for the info so far, hopefully today or tommorrow i can really start digging into it.

I just wanted to update and get some more info. Well I was able to dig into the carb and valves and here is what I have so far. The valves were all a little loose so I tightened them up, still runs like crap. Next I took the carb apart and took a look inside, no problems. So know I am stumped. Here is what I can tell you for sure. The plug was a light gray color, the carb is a mikuni flatslide 38 and the main jet is a 250 and the pilot is a 22.5. the air/fuel screw is 2 turns out. I am guessing that the jet is off but I am not sure where to go. Also when I get it started and running, the idle is rough and it will die, but when I get it running finally and it is just sitting there out of the blue it will make this long PEEONG sound and die. Can someone help me out. Also just to add on it has a WB E2 and a K&N pod filter vice the air box.

Sounds like when its idling the engine 'kicks back' and the noise you hear is the starter and decompressor mechanisms engaging as the engine turns backwards.

Kicking back at idle- pre-ignition? But at idle?


Is there any way that I could check this or how would I go about fixing it. New starter maybe, I am out of ideas for it and it has me pulling my hair out.

Sounds like you are lean or have an intake leak. An intake leak has the most effect at idle. Leaks cause a lean condition. It will also cause a surging idle. To check for a leak you need to have it idleing, so if it doesn't idle it is hard to test. At idle spray carb cleaner on the ends of the rubber boot beween the carb and the engine. When you hit a leak the idle will change.

It is also possible that you are just too lean on the idle. Try increasing the size of the pilot 2 or 3 sizes larger. This is relatively cheap and easy.

Just looking in the bowl doesn't mean the rest of the carb is clean. Crud can get trapped inside the little passages. The ones that go to the idle screw are the hardest to get clean. Use the little tube on the carb cleaner and make sure it flows through all the passages. Put it in one side and make sure you can see it comming out the other of the passages.

I really doubt that a new starter motor will make any difference.

Is there any way that I could check this or how would I go about fixing it. New starter maybe, I am out of ideas for it and it has me pulling my hair out.

Its not caused by the starter, its just something that happens when you rotate the engine in reverse.


I had similar issues with idle on my '94. Turns out it was the idle mixture screw being too lean. half a turn fixed it right up. Idles smooth now. Having an intake leak like Cleonard mentioned could do the same thing if your setting is correct.

Same problem on 2000 xr650 run rough, won't run at all without the choke on. Seems to get hot real fast. Checked carb out has the right jet clean also. I think it is a fuel or air leak on this one just need to figure it out. did you ever figure out your problem. Thanks

Same problem on 2000 xr650 run rough, won't run at all without the choke on. Seems to get hot real fast. Checked carb out has the right jet clean also. I think it is a fuel or air leak on this one just need to figure it out. did you ever figure out your problem. Thanks

This problem sounds like your pilot jet (aka slow jet) not the main jet, is restricted or completely plugged. For some reason this year I have had problems with my son's bike, and my two generators. Gas was only left in each for less than a month. I now drain the bowls everytime after use. I only use so called good quality high octane pump gas and it gums up fast.

Well I hate to resurect a semi dead thread but I am still having issues. I have changed the pilot to a 17.5 and that seemed to help for a minute or 2 and then poof it dies. I have been doing some searching on here and am beginning to think that this is maybe a stator or cdi problem but I am not sure. Here are the 2 biggest symptoms. One day I was riding in about 2nd or 3rd gear and went to pass a car and poof it just died so I had to stop and pull over and then it started up again. Also the other thing is when I start it and idle it it will idle for a minute or 2 then it just has a very violent shutoff and makes a loud noise from the right side of the case. Any thoughts to this would be great.

I would not worry about the noise when it dies or stalls thats normal. And it seems you went leaner on the pilot jet, would think you need richer! Does not sound like an ignition control module. Sounds like an air leak with the popping and backfires an deceleration, or cam timing has it ran like this since you had it? Being hard to start and rough idle sounds as if the cam timing is too far advanced initially. Mikuni flatslide is not a pumper carb, though mikuni does make a pumper, and all that means is that it has an accellorator pump, much like a holley 4 barrel for your old car, you twist the throttle and it gives an extra squirt of gas to get things going. Also are you sure it was a 250 main jet, that sounds way rich, but the 22.5 pilot (slow) jet sounds right.

Yeah, it has ran like this since I have owned it. And I also have found out about the Mikuni, it doesn't seem like the best choice of carb for the 650 but what are you gonna do. I bought it in October and it has never really run that good. I have been doing a lot of research on it and still can't seem to figure it out. I have looked all over for air leaks and nothing, I have checked and double checked the valves and still nothing. The only thing I have found in searches is the CDI or stator. I have a 1999 XR250 and it doesn't act like this at all. I was thinking also sometimes when I can't get it to crank and try to bump start it I can't, it is impossible so I don't know if that would have anything to do with it. Any other tidbits of advice would be greatly appreciated.

Oh, bye the way welcome to TT! Next do you have a manual? I would say its got to be cam timing, you can check it with a timing light, or pull the rocker cover and left side cover and check the timing marks. If you really suspect the ignition you can ohm everything from stator to coil. Goes back to the question do you have a manual?

Yeah I have a manual. I will give it a go this weekend. This has been so frustrating but I guess thats part of the fun in owning a bike. Thanks for your help and I will post up with the results later this weekend.

When you get frustrated, STOP. wait, then try again, take your time, and be methodic! But remember these bikes were designed so that a 10 year old japanese could work on them, but still a manual and a few proper tools helps. Good luck!

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