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I posted about a month ago before I had to go out of state, but can not find what I said. My wife's 60" JD zero turn mower (Yes it is hers) suddenly lost power when she wanted to use it the end of Sept. The mower had been sitting for 3 months unused while we were gone, ran normally prior leaving and having a lawn service mow while we were gone.

Without a load the engine seemed to sound like it running like normal until a load (engage the blades or climb a hill) both normal conditions when she is mowing. I pulled the plugs (I am involved in Land Speed Racing normal thing for me) one was very clean the other was not but had been firing. Talked with the service manager at the local JD dealership, who suggested the problem may be the carburetor. Cleaned the carb. which did not need it, but no improvement, ran it without the air filter, no improvement. Replaced the pump and fuel lines still no improvement, replaced the plugs before the carb work with no improvement.

Before I left 3 weeks ago a poster suggested that maybe the valve train had excess clearance and perhaps a push rod or two had dropped out of the rocker, pulled the covers off today and all 4 push rods are in place, so I am out of suggestions, does anyone have an idea? The only thing left untouched is the HEI ignition, I have had auto engines with problems but most often it is misfire or no fire.

Appreciate Responses

If you have the adjustable valves then you might need an adjustment ............ Or you could have a blown head gasket.... A compression test will confirm a blown head gasket.........

IL Engine knows more than I do on these Kawi's.... He might chime in here and confirm what I said or have another idea on your issue.........

Let us know Mon Ami ~!~!

Did you check the valve lash to be sure it is in spec ? (You should hear it if it is not tho)..

Looking at your engine from behind the machine, is the left (#2) cylinder the very clean spark plug. (Just curios).

Could a critter have crawled up under the housing & chewed on some wires ?

Boudreaux In Eunice La. said:

If you have the adjustable valves then you might need an adjustment ............ Or you could have a blown head gasket.... A compression test will confirm a blown head gasket.........

IL Engine knows more than I do on these Kawi's.... He might chime in here and confirm what I said or have another idea on your issue.........

Let us know Mon Ami ~!~!

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I should have mentioned that I did check the compression, before I pulled the carb, even both cylinders at 100#, valve train is non-adjustable.

Describe what it's doing under load and losing power.

Is it starving for fuel?

pmlock1 said:

Describe what it's doing under load and losing power.

Is it starving for fuel?

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New Fuel pump, fuel filter and all hoses, tested with and without gas cap installed

Sounds like to me that you have an HEI unit dropping out under load, which I see quite often on several brands of engines. And it may not effect the same module all the time. Normally I find on Kaw that when one is acting up with a little testing you will find that both are going goofy. I have engines that will run on the other cylinder when you ground out one plug, and it doesn't matter which plug, which will make both of them seem normal. Neither plug will fire through a spark tester, and if you unplug one spark plug wire and try to start the engine to get it to run on the GOOD cylinder it won't fire. And it doesn't matter which plug, which indicates that both modules are not producing correct output at cranking speed.


And as far as valve adjustment unless they are hydraulic valve lifters they are adjustable. Some of the Kaw's have a bolt and nut that goes through the rocker arm. that bolt is ascentric and you adjust the clearance by loosing the nut and then turning the bolt, which because it is off center adjust the clearances. and then while holding the bolt retighten the nut. Will take several attempts to get it to the correct clearance.

ILENGINE said:

Sounds like to me that you have an HEI unit dropping out under load, which I see quite often on several brands of engines. And it may not effect the same module all the time. Normally I find on Kaw that when one is acting up with a little testing you will find that both are going goofy. I have engines that will run on the other cylinder when you ground out one plug, and it doesn't matter which plug, which will make both of them seem normal. Neither plug will fire through a spark tester, and if you unplug one spark plug wire and try to start the engine to get it to run on the GOOD cylinder it won't fire. And it doesn't matter which plug, which indicates that both modules are not producing correct output at cranking speed.


And as far as valve adjustment unless they are hydraulic valve lifters they are adjustable. Some of the Kaw's have a bolt and nut that goes through the rocker arm. that bolt is ascentric and you adjust the clearance by loosing the nut and then turning the bolt, which because it is off center adjust the clearances. and then while holding the bolt retighten the nut. Will take several attempts to get it to the correct clearance.

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I had an earlier poster that said you might weigh in on this problem, I posted earlier that I have had this HEI problem with auto engines. I have very little experience with HEI in small engines, never had any problems with the bikes supplied to me while I was with Yamaha, they were always new. I will just order out units for both sides if that is what it takes, will have to get far enough along with a couple of projects so I can get back on to my wife's mower and look at the HEI .

The valve lash adjustment is most likely as you describe, as I remember the cross bolt does have a head on each side, must be eccentric, will get in this also after this week, to much going on! But not too busy to thank you for your very informative input, appreciate you taking your time to explain things to me, knowledgeable individuals like you are a real assist to forums like this.

Have a Merry Christmas!

Steve

Hmm...load failure could still be starvation. Don't know the carb used, but secondary enrichment circuits gummed? Perhaps passageways to main jet(s)? You had color on one plug, but other was clean. Runs better on load while still cold? Just ideas. Machine reaching operation temp?

OOPs, Sorry I missed it is fuel injection ? If so there are fault codes?

Some of the newer HEI systems have rev limiters and spark advance electronics built into the module itself. So you can have issues with the rev limited failing causing misfires at lower than normal rpm's or the spark advance system fails and you will still have spark but can and will be out of time.

It used to be that you would either have spark or no spark. Now you can have spark but still have a bad module. If timing was off, you would check flywheel key to see if it was sheared. Now the module can imitate a sheared flywheel key.