Noah

they are the idele mix screws also known as low end or low speed needle, counter-clockwise will unscrew it so the fine tip pulls out of a small hole makeing it bigger so more full can flow, this is richening the mix, which in turn should help with your high rpm idle which is a sign of a lean idle mix, if you have a problem with bucking, sputtering or some other fuel issue at high rpm you need to adjust the high speed needle screw on each carb, good luck. from what I can tell not a long and short screw rather a small redesign of the carb where they resesed the needle screw rather then having it open.

is your tank alittle loose and vibrating with the rough idle? I don't see how the petcok being on RES would effect it other then the slightest in wieght transfer, you may also want to pull the tank off and check the rubber/foam under it, not sure what they used on this bike if anything at all, if they did it could have degraded over time if not then it's a good idea to add some so the tank and frame don't bump and rub, I had an issue on my YZ80 as a kid cause the clutch cable also ran between the tank and frame and would rub.

I would have to agree, it seems like a fuel mix issue, sounds like she runs fine then something heats up and starves her for fuel causeing the reving, you should definatly richen up the high speed needle, if you can easily get at it I would put a screwdriver in your pocket and take her out when she revs pull over and richen by 1/8th turn at a time till reving stops and she idles good again then ride some more if she revs again repeat, if this is obviously not working check for air leaks around the carbs, clogged fuel filter, degradded vacume line. as for the petcok leave it on PRI it will function normaly if not get a new one or rebuild it, rebuild kits are $25usd, could also be the vacume line to the petcok has a small air leak causing the problem, do not just open the petcok this is for draining fuel without removing the tank, in a bind it's okay to get you home but just leaving it there is a bad idea and you will soon figure that out for yourself when you go to get on the bike and realize that your tank contents are on the ground below the bike.

can you help me with where to get a carb rebuild kit for the mikuni bs34 carbs, I've been looking and can't find a rebuild kit anywhere, I did find a place that does full rebuilds http://www.wgcarbs.com/index.php?option=com_content&task=view&id=14&Itemid=29 but they are expensive, I just want a kit that has all the O-rings, gaskets, needles and floats. or some where I can piece together my own kit, thank you.