PTO cylinder runs rough

[upacreek]

Heres how it all started, I was idling around the the lake when the left engine died. I restarted the engine and ran it up to full throttle. It ran up to full speed and ran fine. After I brought it back to an idle it would run for a few minutes load up and die. It did this a few times then started to backfire thru the carb when accelerating. After checking the plugs it seams its the PTO cylinder that is not running properly. Here is what I have done:

Replaced spark plugs
checked compression 130 lbs on both cylinders
removed head and inspect cylinders- no scoring
removed exhaust manifold to muffler pipe- no obstruction
rebuilt carbs on the left engine
switched carbs from good running (right) engine to left engine
ran fuel line straight from fuel tank to carbs
removed spak plug boots and checked continuity
stripped ends of plug wires 1/2 inch to expose wire then reinstall plug boots
switched all wires from left ignition coil to right coil
unplugged voltage regulator
replaced cylinder head ( running out of ideas)

It will start and idle fine. When you accelerate it misses badly, once on plane ( right engine runs great) it trys to run on both cylinders , you can feel it kick in every now and then. Spark plugs show left engine pto cylinder is rich or not firing (black and wet). Sorry for the long post but I am at a loss. The engine is a 657x

 

[Dr Honda]

Well.....



Did you try switching the coils from the left to right engine?


Unfortunately... the next steps will require you to rip into the engine a little. You need to verify the rotory valve... and you need to verify the coils behind the flywheel.

 

[upacreek]

yes, I switched ignition coils and it ran the same. I thought about the rotary valve but it runs good on the front cylinder and idles good on both cylinders.
I,m starting to think something is bad with the stator. Can it run bad on one cylinder and good on the other with a bad stator ? I think it has a 5 wire stator but I'll have to look again.

 

[upacreek]

Took it out yesterday and it will idle good and run wide open good but anything inbetween it pops out of the pto cylinder carb. Think I'm going to pull the engine out after the weekend.