runs fine at low rpm, high rpm no power bogs down

[mjc1279]

Its a 2000 jac 1110 hauler with a robin 350, compression @ 160, valves adjusted. This things sounds great at low rpm, but once the throttle gets to certain point it bogs down, i have tried adjusting valves, adjusting throttle linkage and swapping clutches. I am about to give up any help would be appreciated, anybody have a diagram for the governor and throttle cable, am wondering if it isn't a timing issue. any help would be appreciated.

[ruredy]

Have you adjusted the governor any?

[mjc1279]

Yes I have tried, it seemed to make a light difference. Before adjustment it would completely die, after adjustment it would just bog down but would continue to run. So can you have good compression and fire and still have an internal problem with the connecting rod or valves.

[ruredy]

Does it help if you pull the choke out when it starts to bog down?

[mjc1279]

nope choke kills it.

[ruredy]

It sounds to me as if every thing works great until you reach a certain rpm. Maybe the muffler is clogged up not letting the engine go faster.

[mjc1279]

i actually have a spare muffler, and have swapped them out, i guess its possible that they both are clogged, i'll try running it with no muffler.

[mjc1279]

ran with no muffler, still bogfs down. could problem possibly be pulsar coil or primary coil, don't know much about these, is there any way to test either of these.

[mjc1279]

last night i checked compression again and it was around 165, replaced all vac lines, cleaned carb, changed plugs, removed muffler and it was still bogging down, it appears to be a slapping sound and bogging down, choke doesn't help, i'm out of possiblities unless it could be the pulsar coil, definitely seems like a timing issue. thanks for the replies

[mjc1279]

put spark tester on it and the spark seems to weaken as the accelerator is applied. Do these coils get weak before the go out? or could it be the pulsar coil.