I recently installed a new Mikuni VM30 carb to replace my old VM28SH. The VM30 was prejetted by Sudco, the vendor I bought it from. The pilot jet was a #25 initially. With that pilot jet the bike would only run on full choke. Turning off the choke resulted in the RPMs rising momentarily before falling back down as the bike died.
The tech at Sudco said it was running leand and I needed a larger pilot jet. I ordered a spread of 5 jets, but they only sent 2. I guess they only have two in stock. Anyways I installed a #30. The results were exactly the opposite. It was running rich. It would only start with the choke off. If I turned the choke on, it would die, even when completely cold.
So I guess I need the jet in between these two, the #27.5. I am nervous that this carb will only work properly with one specific pilot jet installed. That seems overly finicky.
While I was working on the carb I also coated all the carb boot parts with liquid gasket.
I also installed a new K&N air filter, the RU-1700. This was the smallest air filter I could find with the right carb mouth diameter. This air filter barely fits. There is a support bar that you have to force the air filter underneath. Once installed the air filter is pushing on the battery on one side and the oil tank on the other. The new carb boot that came with the VM30 carb probably didnt help anything either. Regardless, this air filter is on, and I am sure flows much better than stock. Too bad I never saw the stock air filter courtesy of the previous owner.
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| air filter barely fits between battery and oil tank |