Kawasaki FH641V 21HP acting odd

[Rat407]

Well, here is the explaination the best I can do. The mower runs great, then all of a sudden it starts to bog, like it got some bad fuel, but then clears up. I can mow for a few more minutes and then it happens again. It does this off and on for the hour I have to mow.

Now, the second time I take it out it runs great but does the same thing, this time it would not clear up. Exhaust smells off from normal when it does this. Kind of like it has a really bad miss and no power. When I disengage the blades it runs but you can tell it isn't smooth. So I shut it off and replace the fuel filter and plugs. Mainly because it has been about 200 hrs since I have changed either one and I figure they are do.

OK, new fuel filter and plugs, crank it up and it runs fine for about 30 minutes and then does the same thing again. So I shut it down and get out the blower to clean up the driveway and around the house before I put the mower in the shed to trouble shoot.

Come back about 10 minutes later, crank the mower to put in the shed and it runs fine, go back out and finish what I didn't get done the first time, run about 10 more minutes and it runs great.

Now, I'm thinking it can't be bad fuel because I just got some fresh ethanol free stuff and put in it and have been using it for a while on that fuel before this started happening.

I'm thinking it is a coil. The question is how do you test a coil?

I did notice that the left side spark plug was darker than the right, like it was fouling and burning well. So that tells me that it possibly is that side coil. At $50 a coil, I do not need to spend money on two if I don't have to, or is a good idea to go ahead and replace them both. Total time on the ExMark LazerZ HP is 520hrs.

Thanks

 

[JR]

If you isolate it down to a coil, replace just the one. Its not to common of a failure.

You can use a inline tester to check ignition, it looks like a test light. It will let you know for sure before a 50dollar purchase.

 

[JetStar]

Can the coils be swapped from one cylinder to another? See if the bad burn moves to the other cylinder.
Do you have a fuel system venting problem?

 

[bubbatime]

Drop your spark plug gap down to 0.020. Will get you a little bit more life out of your dying coil. Start shopping around for a replacement coil, as yours is going out.

Now is the time to clean the engine as well. Blow off any grass or debris from the cooling fins to make sure that your engine is not actually overheating.

 

[Rat407]

I checked the fuel caps and they operate normal. Allowing air to vent into the tank but not allow any fuel vapors to exit or splash out of the vent.

Going to tackle this some time this week. Work has me busy so it might be a few days.

Good idea on swapping the coil to see if it affects the burn of the other side plug.

At least coils are easy to replace, just not wallet friendly.

 

[MiKe3o]

There might be a thing called an igniter in the coil circuit. Most kawis have them
Works with the ground of the coil and I have seen it cause issues like you describe. Coils don't fail often , not much there to fail.

 

[Rat407]

Just in case anyone is following this. I found the problem. When the mower started to act up, I pulled a spark plug. I started on the right and it kept running, but when I pulled the left one it died, so that told me it was that coil. Good feeling to find the issue and it only being a $50 coil.