I have almost got my 650l dialed in. It was running entirely to rich. Plug was black after 200 miles. I pulled carb re jetted from 58 165 needle 3rd clip to 55 165 needle 2 1/2 clip(shimmed). Changed oil to syn, spark plug. Also while I was there I drilled my slide as per DAVES MODS. So now Dave mods are complete, with a full yoshi wrapped header/exhaust. I have no engine mods. It is so smooth and freakishly strong! No coughing/popping after dropping the hammer then decelerating, just at the verge of wanting to. So I now have the luxury of really dialing in the fuel mixture screw/and idle. My problem is that when I put the hammer down when the light turns green, then slam on the brakes at the red it wants to stall going from all out, to clutch in slamming on the brakes. WHY? Seems that I can turn up the idle a little, or increase mixture to stop the stall, just cant find the absolute perfect mix of the two.
Next item is the air box. I have de snorkeled but I got to wondering if it would help to cut the piece of plastic which comes down about 1 inch across the box at the opening of the air box. What is its purpose?
Next item is gratitude!! Thank all of you who post your info and help others. I have learned everything to do on my bike from you guys. Researching this forum can tell you almost anything you need to know. If you cant find it, then all you have to do is ask!! I will not take my bike to a shop anymore (until major motor overhaul) because of the info and resources here! Plus if you break down it really does pay to know your own beast so you can get home.
Now for all you smart ass sobs out there. I know I can purchase another much better, expensive after market carb. Not what I want to do right now(but if you want to help a brother out)!!

Thanks again

Turn your idle screw in a bit to speed up the idle! No?

Mmmm, sounds like you are using the dynojet needle and perhaps main jet, so I might be a little off, but you may do better with a 55 main jet.

How far out is your low-speed fuel screw?
Less than 2, pilot prob. too rich, more than 2.5, pilot too lean, but that dynojet main jet and needle are going to make it rough to peg the right combo ahead of time.

I think the plastic piece in the airbox won't make much airflow difference, but there is a secret dave-mod.

take off the left sideplate, and look under the seat, how the heck does any air get to the top of the airbox?
My seat has some holes in the cast-in bracing to get some more air under there.

Dave

My 162 main came in so I broke it down and re jetted again. Problem solved. It was just getting to much when giving full throttle then close it down. Was having to adjust idle screw to high to keep it running when slamming to a stop! Pulled me to 95 with no problems. It just wanted to pop, and occasionally would, but only going from full throttle, to closed at high rev deceleration. I believe I have nailed it at this point. I will drive for 4-500miles do a complete plug, oil change, and evaluate it then. If any correction is needed I believe I will only have to adjust needle slightly. Hope this info helps someone else!

Well I did about 400 miles and pulled the plug. Black again! Not as black, but black. I now re jetted down from 55 to 52, went up from 2 1/2 to 3 1/2 on the needle, down from 162 to 160. Thought for sure it would do nothing but pop and crackle. Ran well with power. Will try a couple more tanks. Then check mileage and plug again. At some point I will have to reach bottom. Cant imagine that it will go lower than 52 slow jet. Possibly could go down on needle and go to 158 main. Should get a hell of a lot better gas mileage!!

xr650l bum said:

For what it's worth I still have that same problem with the mikuni I put on last year. Plug is perfect,bike runs with more power. Just some thing I learned to except.

Any update on this issue on this thread? I am wondering because I have a 2008 with 2205 miles on it and have the same problem. Just wondering if there was an overall prefect setup that you have found? Thanks in advance for any help!

All stock jetting?

55/158 is a good place to start if you have a new silencer and a foam air filter.

OK so I've got this '94 650L with the stock carb that I recently reinstalled. I had an FCR 39 carb on it for a while but it was such a pain getting my jerry-rigged boot adapter to fit on the thing that I put the stock carb back on. It was jetted at 55/160 with Dave's mods. It ran like garbage. I opened up the airbox and that helped significantly, BTW, it's a stock exhaust with a UNI air filter.

It began to have a bad problem of hanging idle with stalling coming to a stop. I found an air leak at the cylinder head so I got a new o-ring. That fixed that problem for the most part. But it didn't fix it entirely. I got a dynojet kit and installed that. I didn't use the spring but I did use the needle. The main jets the kit came with were way too rich. I settled on a 158 main with the dynojet needle set at its leanest clip. But it still wasn't right. Power was better, but the bottom was off. I went to a 52, then a 50 and finally a 48 slow jet. The pilot is set around 1-1/2 turns out. The dynojet kit was expensive considering I only used the needle but that needle seems to be the hinge on which the rest of the jetting turns. I think it was worth it.

I always enjoyed riding the XR-had it just over 3 years now- but it was never impressive power-wise. Now it is. It's never had low end power before. I deliberately short-shift it now because the low end grunt is so intoxicating. It will now chug happily through deep sugar sand all the way to WFO without a hiccup.

Oh and my gas mileage was always crap around 32. Now it's around 42 mpg. Bonus.