Kawasaki FH770D 28HP sputtering under heavy load

Are your gas caps venting. ?
Fuel valve operating properly ?
When it starts running poorly...remove the fuelline and check the flow..
I wouldn't think it would be electrical...it would show up on the sparkplugs..
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Gas caps are venting. I took it out yesterday and with all the bumping around I can see small moist areas near the hole so I think they're ok. I assume the shut-off valve is ok because I've left it closed before by accident and it killed the engine. Opening it allows the engine to start up and run fine. I see the same amount of fuel in the fuel filter all the time...but at some point if if keeps getting worse I'll make a point to check the flow. I did already replace the fuel pump.

Yesterday I tried some Lucas fuel system cleaner and I'll run that through and see how it goes. I'm also running some Star-tron in it and I've used that off and on in the past. I'll see how it goes on the next mow. http://mystarbrite.com/startron/

 

I still have the problem and it seems to be getting worse little by little. Just so you know, the mower has only 170 hours on it, it's stored indoors when not in use and it's only used about 2.5 hours per week at my house.

Here's what I've done so far.
- Checked condition of plugs. They look clean, no black and not fowled. Look great to me. They were new as of this spring anyway.
- Checked flow of fuel by disconnecting the line that goes to the carb and put a hose on the fuel pump on that outlet. Started engine and fuel flows quickly out of the hose.
- Checked fuel filter (blew through it and it looks clean - it was replaced this Spring)
- Checked/cleaned air filters (they were new as of spring too)

I've been using premium gas. I ran a couple cans of fuel system cleaner through the gas too after this problem came about. No help.

Do you think the carburetor is dirty inside? Could that be it? Would it be worth the trouble to take it apart and clean it out (remove the bowl, jets and spray it with carb cleaner). I hate to take it apart if I don't have to though.

The governor seems to work fine. The engine speeds up when under a load like if you take off quickly or start up a hill from a stop...you'll hear the engine kick up in speed.

This couldn't be electrical could it? The way it's acting, it seems more like a fuel issue (carburetor dirty?).

In the past I could engage the blades at half throttle, which is what I think you're supposed to do anyway to be easier on the electric clutch, etc....but now, if I don't have it at full throttle it'll nearly kill the engine when I engage the blades. Even at full throttle, when I engage the blades, the engine slows down and sputters like crazy, running really rough until the blades are up to speed. Then when I start mowing, if I run into some thicker grass and I'm going 3/4 speed or so, it'll start sputtering like crazy again until I slow down so it's not under so much load. Basically, a heavy load is what triggers the problem. Otherwise the engine runs really smooth and sounds great.

 

Sounds like a carb issue...a good cleaning should help...
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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

 

Good news. I decided to take the carb apart and spray it out with carb cleaner. I took the bowl off and also the top plate. I sprayed carb cleaner in every hole I could find. When I put it back together, it still sputtered under heavy load or even a little before heavy load, but after a few minutes it ran strong and plowed throw thick, tall grass in the field (as a test) with no sputtering. It sounds good now. I'll keep an eye on it but I think that's what the problem was. Also, the fuel filter is nearly full of fuel all the time now. Before, it looked nearly empty which I though was unusual.

 

I guess I spoke too soon. Took it out again yesterday for 20 minutes or so and the sputtering under heavy load is still there and very bad. Frustrating...

 

Ok...so knowing what I said in my previous post about cleaning out the carb, what suggestions would you have at this point? Could it potentially be coil related like someone else mentioned? The only thing that makes me skeptical about that is how it only happens under a heavy load when the engine is struggling with tall grass or starting out on a hill with the blades engaged. I would have thought a coil issue would be more consistent and not only happen when it's under a heavy load? Could it still be the carb (maybe I didn't get it cleaned out as well as I thought)?

 

EDIT:
I was just reading some more on here about the coil problems people have had in the past. I'm going to start it up and pull off each plug wire one at a time to see if it runs any differently or dies. It should be an easy way to tell if each plug has spark.

 

I just fired it up and pulled each plug wire off to see how it sounds. For each plug wire, when I pulled it off, there was an obvious change (rough idle and audibly sounded as if one cylinder was now not firing. I did this for each side and it sounds the same when one or the other plug wire is pulled off. So, I think the coils are working fine in this scenario. My question is though, is it possible that they could be failing under a heavy load? Could a coil problem present itself JUST under heavy load?