trouble with SATOH Bison

[bensonhurst]

Last summer I started to have some trouble with my Sato S650G; which I've had for about 26 years.
When under load (at full throttle) it would die of, what appeared to be, fuel starvation.
This is ONLY when under load, which for me meant, cutting the grass with a Woods RM600 mower deck.
After checking out all of the usual culprits I finally took the carburetor apart and found it very dirty, I cleaned it out; and that seemed to do the trick.
Over the winter I replaced ALL of the ignition parts (everything) and installed an electronic ignition which replaces the rotor, points and condenser.
Now I have the same fuel starvation problem, only under a load and after the motor has warmed to operating temperature and at full throttle.
I know it's NOT fuel starvation but it has all of the symptoms.
Full throttle without the PTO engaged is no problem.
The mower deck is NOT bound up and the blades turn easilly by hand.
Any ideas?

 

[Outlander]

If you used a carb kit and it had a float valve with a viton tip, it may well be sticking. Those rubber tips are nortorious stickers. If no kit you may have inadvertently (of course) bent the float arm and messed up the float level. Or maybe got a jet in the wrong hole? Sometimes the only difference in jets is the ID and not the OD. How sloppy is the throttle shaft? What do the plugs look like? Usually Jap carbs are pretty good unless some "expert" got in there and did the magic that only "experts" can do......Many older carbs go this route.

 

[PILOON]

Well, being a gas engine you have (not sure on tractor as mine is fuel) a distributor and and some sort of spark advance system.
Vacume and or mechanical.
If vacume could be an air leak?
If mechanical the small weights and mechanism could be crudded and or rusted limiting the advance.

The mechanical advance the 'guts' would be in the base of the distributor.

 

[mit]

there could be a miswired ignition system causing your problem.double check the wiring.

 

[bensonhurst]

DONE, FIXED.
I took the carburetor off and cleaned it out thinking, just maybe, there was some dirt I missed last year. When it came off, I noticed the gasket under the carb was cracked.
As the crack appeared to be tiny, and very minor, I put the carb back on without replacing the gasket.
It started right up but still wasn稚 running smoothly, so I took the carb off again and made a new gasket and voila everything was fixed.
It idles smoothly and runs at full throttle, under load perfectly.