Quote:
Originally Posted by Weldangrind
The 30mm Mikuni that I'm familiar with has the pilot mixture screw just under the transition from the carb to the intake tube. When the screw is in that position, it controls fuel.
On a typical two-stroke, the screw is at the air filter end of the carb, and it controls air.
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I'm still sorting out my pilot size, after making 4-5 orders (still not satisfied with size) I decided to order every pilot jet (and Main Jet) in even 10s up to the max size Jets-R-Us sells so I don't have to keep placing orders except to fine tune. It appears that this fuel or air screw in question is actually an air screw. The typical Mikuni (not that this VM26 PZ30 is really a Mikuni) that has the pilot screw in the rear near the manifold makes the pilot screw an air screw. It meters air to mix with fuel in the pilot jet. I've had my "air" screw unscrewed to allow more air in and it did make it lean and start to cough, and when I screwed it in, it went rich and loaded up. Even the UFO instructions refer to this being an air screw on the VM type round slide carbs. I believe Mikuni makes carbs with both air and fuel screws on different models. From my understanding is if the screw is in the back of the carb near intake manifold (cylinder head side) then it meters air and if its located on the air filter side it meters fuel. I know the Keihen carbs have fuel screws because that is what I purchased that actually fit the Mikuni but as a fuel screw. Weird hybrid Chinese copy. I'll go back out shortly and try the screw in near full in and check plug and also at near full open and check plug and see if I can absolutely confirm this. I've been getting a lot of conflicting feedback from the carb, jets, plug reading, running conditions.