Hello all, I just moved from so cal desert to Idaho so looking forward to a little different riding. I was messing with the 400 today and trying to get the jetting perfect and I have a question. I have the mikuni carb and a pipe with a uni filter, my bike is hard to start hot and I still have a flat spot, I turned the fuel screw in untill it started to sputer then went out with the screw and it never died. I must have been 5-6 out, does that mean pilot is to lean. I think it is the 15 in there now. The carb came with a 17.5 also and the 12.5. I'm about 4000 feet. Thanks all anyone in boise to ride with. Dan

With the engine running while making the adjustments, turning the screw in(Leaner) will eventually make the engine die, but if you're expecting it to die as you come out with it(richer) nearly all the way, don't hold your breath. Don't use the fact that it doesn't die at the end of the screws useful travel out, as a sign that it needs a bigger pilot. The "too rich" signs can be more subtle than that. Engine idle will drop and become rougher but not necessarily make the engine die. Throttle response off idle will be worse too.

The 15 pilot for 4K should be good. What pipe are you running? Snorkle out?

Make sure you have the pump come on screw set all the way in so the pump comes on late as possible. If you have it set so the pump comes on right off idle, it's gonna sputter and hesitate.

I am running a xr's only muffler, my stock carb was 155,55. when the bike is hot a have to kick 4-5-6 times to start, is'nt that a sign of lean pilot? anyway went to the 17 today rode it around the block seamed pritty snappy, started right back up, going out next weekend so I'll see how it runs on the trail, thanks all.

Ok one more problem, I put a 17.5 from a 15 pilot in the pumper carb,(had problems starting it when hot). 4000 ft no snorkle. went out riding today, bike started first kick to get going and ran great, if I stoped for a short time to let some people catch up it would be anywere from 1 kick to 6 kicks to start it, anyone know why. then later in the day clouds rolled in and it started to rain and the bike would not idle, could I be to rich or still to lean on the pilot. Thanks all for giving me direction to go.

Make sure too that you're not running your idle too low. XRs don't like a slow idle when it comes to starting.

With the Mikuni, for restarting, what I've found works best is to kick from TDC just like always, but at the bottom of the kick, crack the throttle.

Where do you have your fuel screw set with that 17.5? I still bet you're rich on the pilot.

I think you are too rich. I know when I ride in higher elevations that I have to lean my main out or it will pop out of the exhaust on decaleration. Most of the time I ride from 1000 to 2000 feet and run a 130 but when I ride 3500 to 6000 I drop the size down. Last time I ran a 120 main, and my bike ran good. If I leave it at the 130 it is hard to start and pops alot. I first tried to go up to 135 main and it was worse, then I dropped to 125 and it was better but still there. My pilot is still 15.