If the induction system is standard (std airbox, filter) then it would be running way too rich with 125's in the rear, may be contributing to your problem.

I see. I got my advice from Rick Oliver about which jets to use. The airbox has the flap cut off, the snorcle removed and a hrc style tray.

shokrabi wrote: The airbox has the flap cut off, the snorcle removed and a hrc style tray.

All of the induction mods will be your problem. Now that you've mentioned them I would say your bike is running lean!!

You could increase the jet size (size depends on what sort of filter you're running), but you'll always have a lean mid spot when you do with those mods.

Best to...

Return the airbox to standard (or get another one in your case), use a standard filter, standard flap, remove the hrc tray, and use 118/120 main jets and your problems will disappear...

ok, thanks for all the help.