apache snow-FSO wrote on 04/16/13 at 05:05:26:I am getting 60 mpg with about 1/2 in town and 1/2 running 55.
I have a stock muffler, a K&N drop in filter, 147.5 main, 55 pilot with the screw turned out 1 & 3/4 turns, and I raised the needle up .030. I am at around 500 sea level.
I tried to keep the stock 52.5 pilot but it was just too lean. I wonder if the 52.5 pilot with the bleed holes would be better.
The bleed holes don't do anything on our carbs. The bleed holes operate on carbs that have an "air screw" to adjust idle air iinstead of idle fuel. I have tried both with and without bleed holes on my carb, and with an O2 sensor in my exhaust so I could read the difference, and there is none. On our carbs the only metering is through the size of the small hole at the tapered end of the jet.......the bleed holes don't do a thing as they are surrounded by the aluminum carb body and there is nothing that can flow into or out of those bleed holes.
On the third page of the following link - there is a diagram that shows how the pilot jet has both fuel flowing in the bottom, and air from the air bleed screw is mixed through in the Pilot Jet. There is also a description of this on the section that talks about the low speed operation in Section 3.1.
http://www.mikuni.com/pdf/vmmanual.pdf