four strokeing at mid throttle

[mike carter 2]

hey yal,let me first tell about the bike.gt 80 engine,reed valves,transfers port matched,ported piston,exaust and intake port matched,1979 suziki rm 60 chamber with fred c header.sill has stock jets in carb. all on a shwinn blackwell frame.the bike will do 40 + ,and gets there pretty quick.o yea,about 12 13 hundred hard miles on it.heres my problem,it has a hesatation around mid throttle.ive reset the needle more times than i have fingers,both up and down,the fuel mixture screw is set at about 3/4 turn out from bottom.thats where it runs best.any other fuel mix no good.the hesatation is worse when its cold.but almost clears up when warmed up. i just posted some pics on the high proformance thread . thanks

 

[Greg58]

Mike if it is running rich the spark plug should be dark color, it should be light brown on the porcelain. Have you made a test run without the air cleaner? If it runs better you need a smaller jet.