Join Date: Feb 2019
Thanked 3 Times in 3 Posts
There is a fuel mixture screw on the carb, but it's for the pilot circuit so only really affects idle to about 1/8 throttle. Past that the needle is metering the majority of the fuel, so pilot screw adjustments for a mid-range problem will have very little effect. On most street legal carbureted bikes there in an anti-tamper plug over this screw due to emissions regulations. Drill a small hole in it and a small pick usually pops them out without too much hassle.
Stuttering to me most likely suggests a rich condition (lean is usually a bog/loss of power, rich is spits/sputters), and if it's in the mid range I'd probably look to lower the needle a bit. OEM needles usually aren't adjustable, and while you can raise/richen them with a shim, to lower them you will need to get an adjustable needle. Most jetting kits include an adjustable one.
I'm sure with enough fiddling around you could get it to run cleanly throughout the throttle range, but if you're not familiar with carburetor tuning it's going to be a huge amount of trial and error.