Originally Posted By: 01rangerxl
How do the gaskets look between the carb and engine?
Try holding the throttle at the same position when it starts surging and see what happens. If the engine runs fine when the throttle is held in place, it's a governor problem. If not, it's a fuel/air mix problem.
If the carb is clean and adjusted, the fuel is fresh, and there are no air leaks between the carb and engine, then it pretty much has to be a governor related problem.
+1.
In addition to that: you have to do your usual due dilligence by doing the following:
(1) check the throttle plate shaft to body clearance, if it's deemed excessive, you need to replace your carb (small carbs tend not to be over'bored to oversize throttle shaft, not too economical).
(2) check to see if there's any nooks and crannies within your carb: e.g. assuming that there's no hidden rubber o-rings, etc. try dunk it into carb dunking solutions and then clean it afterwards.
(3) carb float maybe off a bit. As carb becomes old, float goes out of adjustment. Need to replace the carb float + needle +seat in order to restore that part.
(4) need to do idle adjustment again. Don't assume that the just because it was working fine before that it shouldn't be adjusted now, for it may be off by just that little bit.
(5) always start by a fresh new air filter (esp. paper filter type of engine). If the filter is slightly clogged (but still passes light test), you still gonna throw your idle air mixture ratio off...
6) whenever you take apart a carb, always consider using a fresh new gasket kit/set. Don't recycle old parts for you'll get into more trouble down the road (e.g. mysterious air leaks of all sorts).
Just my thought on carb rebuild subject.
Q.