Off idle stumble/flat spot.

I got the bike sounding like a sewing machine at idle. However, if I bring it down to idle speed in 1 st gear and hit the throttle theres a stumble then sputtering performance then normal accelleration all within a 500 rpm window. What do I need to do to get it smooth? The plugs are white only on the surface parallell to the top of the piston+ 1/16" up the side. Mixture screws are all 3.25 to 3.5 turns out. I blocked off each tail pipe with a rag so I could hear which side the sloppy idle was comming from. I then adjusted, without a tailpipe blocked, the carbs on the bad running side. I noticed one side is louder than the other but got it to run smooth.

 

Float levels can cause issues with off idle. I would check float levels and did you go through a whole tune up , valve clearance check and carb cleaning, carb sync. (Note: throttle shaft seals that are hard as rocks will leak vacuum and cause problems also)

MN

 

I've got the same thing I'm trying to diagnose right now. I've fully rebuilt the carbs with all new seals/needles/seats. I was thinking float level too because I had a severe PITA setting them on the bench because I'm a dumb monkey sometimes. I have yet to do a plug chop at all, I'll be puting in new plugs tonight and doing a few plug chops all over the range to see what my mix is looking like. The only thing I haven't done is a synch....don't have gauges for it right now. Let me know what you find if you figure it out first.

 

Ill check the float levels again. I set them once and it ran great. Tore the carbs down a bunch of times trying to find out why it would not cold start. My guess was too lean mixture setting but I try to turn out the screws and it starts to run rough.