Kawasaki FH770D 28HP sputtering under heavy load

[LarryF]

Originally Posted by BKTP

M ezmark did the same thing you are describing, and continually got worse until i realized (with help of some fine folks on this site) to look at my coils. Sure enough i was struck with infamous KAW coil failure, the begining stages were just as you are describing.

Good Luck

I'm another homeowner with an Exmark Lazer, and I had the same problem that also turned out to be nothing more than bad coils. Lotsagrass, you acknowledged seeing BKTP's post about the coils but I don't think I saw your response saying "yes I checked that and it's definitely not the reason for the malfunctioning". Checking the coils is a pretty easy thing to do. All you need to do is take a resistance measurement. I didn't even have to remove the coils, just the spark-plug wires.

[piston slapper]

Another thing to check...
When it starts acting up..give it a little choke and see if it improves..
This will richen up the fuel and let you know if you have a lean condition ..and possible intake gasket leak.

[lotsagrass]

Thanks. The plugs looked very clean and normal to me. Not fouled, wet or overly white or anything like that. I tried pulling the choke out a little but it actually makes it slightly worse.

My last resort is the coils. I'll see about checking them with a meter soon. I saw the procedure in the book, but I guess I can measure them one way with just using the meter lead on the plug wire and I assume ground to the engine. If measuring the resistance that way will tell me something, great. It will be easy enough to check.

[piston slapper]

Measuring resistance that way will get you in the ballpark...close enough..

[blabarre]

I actually tried the method of pulling the spark plug wire from the spark plug one at a time while the engine was running. neither one died when pulled seperately. so I am assuming that the coils are not completey bad. Could they still be bad even though I did that test?

[taxidermist]

Originally Posted by lotsagrass

I checked the plugs today. They look great. Very clean. I confirmed that I did change the plugs with new NGK plugs this spring. I found the old boxes I kept to get the right part number again next time.

Try another brand plug.......this is a common problem with NGK plugs under a load I once had a ferris come in to the shop just like mine and I swapped parts until I found a bad plug. I took out the bad plug and put it in my mower and it did the same thing. I changed both plugs to a champion and no problems since.

I like NGK plugs and I use them..... but i have had them go bad and also a bad one from the start.

Cant hurt to try.

Rob

[lotsagrass]

I just checked the coils with an Ohm meter with the coils still attached to the engine. From looking at the service manual, the only check I can't do is the check between the kill wire connection and the other terminals.

From my understanding, position A in the illusatration is the part that's grounded to the engine so using the engine itself should get me to that one....and the plug wire is the one marked C in the illustration, correct? So I should be looking at the reading between A & C? If so, I think my readings are fine for the coils. Well within the specs listed in the book which is a range between 14k and 24k, right?

I put my notes on my actual readings in the yellow box below. Can you confirm that this looks ok to you too?

[piston slapper]

Your readings are within specs...but...one is at the low limit..and one at the high limit..
I would expect them to be about the same..both being off the same engine...
Reading the coils when hot may actually change one or both of these readings into the bad numbers...

[lotsagrass]

I checked it when it was cold. I took it out for a spin again this afternoon into some really thick and tall grass in the field. It sputtered a few seconds after I engaged the blades, but in less than a minute, it was plowing through the grass with no sputtering. You could tell it was stressed (normal sounds of an engine under heavy load), but no sputtering. I'll see what happens over the next few mows and if the sputtering keeps coming back I'll go ahead and do the plugs and coils next.

[70marlin]

The pro's know best! My kohler magnum MV20, this spring did the same thing. fuel filter, pump, fuel line replaced, cleaned & flushed fuel tank the hole bit. turned out to be the carbs float needle. Replaced the needle ran a couple tanks of sea foam and fuel through the mower, problem went away. I normally store the mower dry during the winter, last year I got lazy just added stabilizer and put her away. This ethanol fuel were being forced to use sucks and wrecks all rubber in our equipments fuel systems.