Mikuni piston gets stuck

[michaelks]

I was cleaning my carb and while checking i found the piston was getting slightly stuck in its closed position.

There was in fact a dozen cotton tips' worth of an oily goo at the bottom of the grooves the piston slides in (the nooks right above and below the needle hole) , which surely was why i was experiencing a jerkiness at the throttle, since i suppose there would have to be a vacuum buildup to free the piston, and then a surge would follow. Now it's much better, very smooth acceleration.

 

[Motor7]

Congealed ethanol would be my bet...the stuff is insidious.