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I have an Exmark Zero-Turn with a 29 HP EFI Kohler engine. The engine has 1645 hours on it and when the PTO is engaged it bogs down when it runs into heavy grass. The Kohler Engine manual shows an diagnostic computer to troubleshoot the governor but I haven't been able to locate it on the mower. Any suggestions where it is located at? I would appreciate any help. Thanks.

First try unplugging spark plugs one at a time, sounds like you might have a dead cylinder,

When the engine is running do you have a MIL light on the dash that is lit. Which would mean stored trouble codes. You could try the key on,off,on, off, on sequence to check for code. the diagnostics computer is a separate software program available to dealers to connect to the engine like they do on a vehicle.

First try unplugging spark plugs one at a time, sounds like you might have a dead cylinder,

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This is actually a great way to burn up a coil. The energy is still being created, and will simply burn its way through the insulation in the coil to find "ground". Instead, disconnect the 12V side of an individual coil, OR place a spare spark plug into the cap and allow the plug to spark harmlessly against the outside of the engine.

I’ve never burned out a coil by disconnecting the spark plug wire to see if both cylinders are firing. Yes, it may happen, but you would have to run the engine for a long period of time before doing damage. Testing this way would take less than a minute.

You can always get up a petition to recall your governor !!

The engine has 1645 hours on it and when the PTO is engaged it bogs down when it runs into heavy grass.

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Lots of small maintenance issues can cause low power. Try...
• New fuel. Standard pump gas goes stale in about 8 weeks. Especially if it's allowed to sit. Especially if it's allowed to sit without a fuel stabilizer.
• When fuel sits in any storage container INCLUDING YOUR LOCAL GAS STATION, the Ethanol comes out of solution. It is possible to get a much higher percentage of Ethanol than what the label on the pump says. Only buy fuel at stations that sells LOTS of fuel because Ethanol contains much less power than gasoline.
• Because ethanol comes out of solution in your containers, you need to use a fuel stabilizer (such as StarTron) in your main fuel storage containers so that stabilized fuel works its way into ALL your lawn equipment. One-half ounce per 5 gallons is all it takes.
• Tight valves can cause low compression and thus a loss of power. Adjust your valves.

Born2Mow said:

This is actually a great way to burn up a coil. The energy is still being created, and will simply burn its way through the insulation in the coil to find "ground". Instead, disconnect the 12V side of an individual coil, OR place a spare spark plug into the cap and allow the plug to spark harmlessly against the outside of the engine.

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Please read threads carefully before you start to type
Your participation is very welcome but it would be more welcome if it was both correct and pertinant .
This post is neither
Firstly the engine has a magneto, not a battery coil so there is no 12V anywhere
Secondly you can not burn out a magneto armature by having the secondary circuit open.
So the post quoted above is both incorrect and not relevent .

bertsmobile1 said:

Secondly you can not burn out a magneto armature by having the secondary circuit open.
So the post quoted above is both incorrect and not relevent .

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Battery or magneto ignition, it makes no difference. The energy created in the secondary has to go somewhere. Now possibly this particular coil or magneto design has a spark gap built into the unit as a safety device in case the secondary wire falls off. You are correct, I am not familiar with the particulars of this mower ignition. However, I'll stand by my central statement that the best practice is to provide an energy path to the block by installing another spark plug in the cap as an escape route. It may not be required, but it certainly doesn't hurt either.

All the best.

The only way any current from a battery can reach the coil in a magneto ignition system would be through a shorted ignition switch and then it would be nearly impossible. They are two different circuits, plus the secondary circuit in the coil is connected to a ground and the spark plug. The switch would be shorted between the B and M terminals on the switch and then somehow back feed to the coil. How I have no clue as the M terminal will go to a ground. Bert is correct, your post is incorrect and also irrelevant because of how a magneto ignition system works. After doing a little more research you would have to have a faulty key or shut off switch on today’s lawn tractors with an automotive style battery ignition systems. Current going to the coil is controlled by this switch.

this is a fuel injected engine, it has 12 volt coils. the coils have power at all times with key on. the computer grounds it to make spark. have yet to see a coil fail.I do a lot of fuel injected engines

Rivets said:

I’ve never burned out a coil by disconnecting the spark plug wire to see if both cylinders are firing. Yes, it may happen, but you would have to run the engine for a long period of time before doing damage. Testing this way would take less than a minute.

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The old LawnBoy electronic coils were bad for crapping out if you didn't ground the plug wire if you took it off the plug and cranked the engine. Force (chrysler) outboard engines were bad for it too. Lots of Force outboards got retired because the ignition modules went out and they were NLA. I haven't had a modern coil go out but i am sure if you ran it long enough disconnected it would.