This has me stumped.

[David Wayne]

My mower has a Kawasaki FH680V +- 1400 hrs. Lost power ran rough- no spark on right side.
I replaced both coils and plugs and thought it was fixed runs smooth as silk, but at anything above about half throttle and it loses the left cyl. I have checked spark to ground and it throws a strong half inch spark, set valve lash on both sides, cleaned carb, swapped coils and plugs side to side, confirmed the choke is not closing, tested compression 80lbs on right its the good running side, and 90lbs on the left. I don't know what to do next short of a complete teardown and I never was confident in rebuilt small engines. Any ideas ?

Thanks,
David

 

[dodge man]

A problem with the valves or cam? Just a wild guess. You might switch coils and plugs side to side to make sure the new coils and plugs are good.

 

[oldnslo]

Does that model have both coils and igniter for each cylinder? If yes have you checked or replaced the igniter?

NOTE: Not 100% positive igniter is correct term but it is what sends signal for spark for each cylinder.

 

[MossRoad]

My mower has a Kawasaki FH680V +- 1400 hrs. Lost power ran rough- no spark on right side.
I replaced both coils and plugs and thought it was fixed runs smooth as silk, but at anything above about half throttle and it loses the left cyl. I have checked spark to ground and it throws a strong half inch spark, set valve lash on both sides, cleaned carb, swapped coils and plugs side to side, confirmed the choke is not closing, tested compression 80lbs on right its the good running side, and 90lbs on the left. I don't know what to do next short of a complete teardown and I never was confident in rebuilt small engines. Any ideas ?

Thanks,
David

If you swapped coils and plugs and that right side is still not working correctly, you can eliminate those as the problem for now.


Here's a link to the electrical on that engine. Maybe it'll help you out.

https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/kawasaki/4-stroke-engine/fh680v/fh680v-as23-4-stroke-engine-fh680v/electric-equipment

You might take a look at the 59031 charging coil.

https://www.jackssmallengines.com/jacks-parts-lookup/part/kawasaki/590317009

It could have a break in it that opens up at high RPM/temps. I had a chainsaw that would do that.

 

[David Wayne]

I did swap side to side, and before I did that I put the old coil back on that side, it didn't help so went back to new coil. Yes it is two coils and the trigger when the magnet on the flywheel passes them.

 

[David Wayne]

Wouldn't the charging coil effect both sides?

 

[MossRoad]

Wouldn't the charging coil affect both sides?

You'd think so. But if you think about it, it's keyed to the crankshaft. So a bad portion could be going past the bad cylinder's coil on every ignition stroke.

Anyhow, since you've changed everything else, what's left?

 

[zzvyb6]

Fouled spark plug from excess oil contamination. Change brand of plugs. Been reported as poor quality.

 

[WinterDeere]

If your Kawi v-twin is like mine, they are somewhat sensitive to flywheel/coil gap, so obviously make sure that's right. You rmanual should have the number, and it's an exercise is moving the magnet under the coil and pushing it down onto a feeler gauge while you torque the mounting bolts. Simple but tedious.

If a dual spring model, obviously make sure your inner valve spring isn't cracked, causing valve float at higher RPM.

All of the Kawi v-twins (I believe) suffer from valve guide slippage, which can cause a bent push rod or rocker arm damage. This reduces overall valve lift, which is a real problem, but I wouldn't expect that to be so dependent on RPM.

Clean / un-fouled plugs are obviously important, but also not so distinctly dependent on engine RPM.

 

[oldnslo]

I did swap side to side, and before I did that I put the old coil back on that side, it didn't help so went back to new coil. Yes it is two coils and the trigger when the magnet on the flywheel passes them.

One trigger or two triggers, one for each cylinder?

Did you check for spark when engine was hot?