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Kawasaki fh721v only running one side

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engine repair kawasaki mower advice
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Mauler40

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Discussion starter · #1 ·
I have a Kawasaki FH721V twin valve on my John Deere zero turn mower. It starts fine but only is running one side of the engine. (I know there is probably a better way to describe "one side", but I dont know how to say it better... didn't want to say one piston or one valve and lead someone down the wrong path.)

The engine idles fine but stalls under load. When I push to high throttle the governor tries to increase the throttle but almost immediately the rocker drops back to low idle.

Anyway, ive replaced fuel and air filters, and spark plugs. I swapped the spark plugs to check them and verified the same side of the engine is not firing regardless of which plug is where. I can pull the spark plug wire from the non-working side and the engine doesn't even notice.

Reading an earlier thread it sounded like my ignition coil might be bad. $100 later I've come away with expensive training on how to replace a coil if one does go bad in the future, but it wasn't the problem here. No change after replacing the coil.

There was a lot of caked on dirt and grass around the fins near the coil I replaced. I broke this up and vacuumed it out.

I'm at a loss. Could this be as simple as something gumming up the carburetor or would the engine not run at all i that case? Any ideas on what to check next?
 
Discussion starter · #3 ·
Valves are definitely the issue. Looks like it did overheat. I found bent push rods and a melted gasket. Attached is a pic of how it looked when I found it.

Not sure if this helps or is relevant, but the top spring can be compressed a small amount with hard thumb pressure. The bottom one I can't get to budge with just hand pressure. Haven't tried anything else.

So, what to do next? How do I determine whether there is more damage I cannot see? If I just order a replacement gaskets, rods, and valves will that likely cover it?

Engine has 325 hours on it. Here is a link to the model parts diagram.


Thanks for your help!
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#6 · (Edited)
Mauler40 said:
So, what to do next? How do I determine whether there is more damage I cannot see? If I just order a replacement gaskets, rods, and valves will that likely cover it?
Click to expand...
Look, yer gonna have to pull the head and inspect the valves /guides closely. The guide/s may have moved in the head, the valves likely siezed up intermittently.
May need a new head assy.
Search on here fer "Kaw. valve guides", it's been discussed several times.

I would pull both heads.

Man, them are AIR COOLED motors. Ya gotta keep the cyl/head fins clear/clean of caked on dirt, debris. Notice the space around the guides, that gets clogged easily.
I use a blow gun with a piece of steel brake line soldered on the end to poke around all the fins and cavities. Ya gotta pull the motor shroud periodically, right ?
 
Discussion starter · #7 ·
No longer under warranty unfortunately.

I will try to replace the rods, gasket and reassemble before I pull the head. Maybe I could get lucky.. could doing this cause further damage or has whatever been done been done?

Will read up on Kawa valve guides, thanks for all the advice!
 
#8 ·
Mauler40 said:
No longer under warranty unfortunately.

I will try to replace the rods, gasket and reassemble before I pull the head. Maybe I could get lucky. Could doing this cause further damage or has whatever been done been done?

Will read up on Kawa valve guides, thanks for all the advice!
Click to expand...
Yer call.
It's pretty much a lead pipe cinch yer gonna be wastin' yer money...but it is yer money, right ?
 
#12 ·
Mauler40 said:
I will try to replace the rods, gasket and reassemble before I pull the head. Maybe I could get lucky.. could doing this cause further damage
Click to expand...
Yes, it could cause further damage. Pulling the head is easy, and the cost of the gasket should be minimal. Pulling the head may reveal no sign of other problems, but the time and cost of doing so is so minimal that I absolutely would do it. Even if I could not do it myself, I would pay a shop its labor rate to do it.

Of course the damage may already be so great that you are looking at a new engine, in which case slapping it back together without further inspections could get you that nice, new engine a little quicker.
 
Discussion starter · #13 ·
Thanks for the advice, I resisted the urge to just put new rods in and glad I did. Pulled the cylinder head and sure enough one of the value guides is pushed out. I will be ordering another cylinder head, head gasket, value cover gasket, and push rods.

Not sure if I need new valves or not. I've attached photos of the values - can someone take a look and advise on replacing? They are not bent, but there is char around the head and you can see the second stem looks warped near the valve end.
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I've also include a photos of the piston head. Is that black char normal or a result of my overheat? Should I get it off?
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Discussion starter · #15 ·
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Attached are pics of the cylinder. Some carbon on the walls but still bright enough to reflect much of the piston head under the camera flash.

I have not pulled the other head. Since that cylinder was still running and powering the mower, what am I looking to determine there? Will it help determine whther the engine needs replacing and that id be wasting $300 to put a new head on the overheat side?
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Mauler40
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