Kawasaki 23hp Engine Backfiring On Hills


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Old 04-17-19, 02:37 PM
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Kawasaki 23hp Engine Backfiring On Hills

I have a six year old Toro Timecutter. It's a 50" deck and has a 23 hp Kawasaki mower. The other night when I was going up or down hills it would backfire something fierce. I'll say, this was the first use of the year. Tonight, I played with it a little more, it won't do it with the blades off. So it seems like it's related to when the engine is under load. And it is definitely aggravated by inclines.

The air filter needs replaced so I'm doing that along with the fuel filter this weekend.

What else do I need to look after here? Can a bad belt cause thist? Are there tensioners somewhere in the belt system that I need to check?
 
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Old 04-17-19, 02:53 PM
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Sounds like all engine. Probably fuel and likely carburetor if it worked fine when you used it last year.

I would try Sea Foam first.
 
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Old 04-17-19, 06:46 PM
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Thank you for the reply. There was definitely still some fuel in it. Maybe 1/2 gallon, but then I poured some more on top of it. I'll drain it out when I'm doing the fuel filter just to eliminate variables and I'll be sure to start it back up with sea foam.
 
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Old 04-17-19, 07:07 PM
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Yep, definitely drain it out and rinse the tank a little. Then put a quart of gas in it with a double dose of Sea Foam. Let that run for about five minutes and sit for an hour. Then fill the tank with a normal dose of Sea Foam.
 
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Old 04-19-19, 01:32 PM
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So it's definitely better, quite a bit better actually, but not all the way there. Is it reasonable to expect that it might take multiple Sea Foam applications for full effectivity? Certainly it didn't gum in only one instance, so I probably shouldn't expect full cleaning in one instance, right?
 
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Old 04-19-19, 02:13 PM
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More than likely its a coil pack that is going bad, very common with Kawasaki engines.

My 17hp Kawasaki walk behind started backfiring/missing and it would occur at higher rpm/load that I could not get to the spark plugs fast enough to determine which one was the problem.

Got a new coil pack, picked one cylinder and got lucky has run perfect for the past 2 seasons!
 
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Old 04-21-19, 07:17 PM
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Back with a vengeance. Is there any way to diagnostically assess if it's a coil pack?
 
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Old 04-22-19, 04:27 AM
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Google it and you will find ways to bench test the coil but as you noted its acting up when hot and experiencing load.

Here is link to other fourms!

https://www.lawnsite.com/threads/kaw...roblem.293008/
 
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Old 04-22-19, 05:21 AM
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You apparently still have the problem? The Sea Foam helped but didn't fix it and the engine was running fine last season and this problem started with first use this year?

To clarify, is the engine backfiring all the time? You mentioned it does it both up and down inclines. Kawasaki engines would have an igniter to go with the coil packs. That may be a possibility.

Testing coils for resistance is usually a standard, but often that test includes replacing with a known good one if it still doesn't work, so you may as well start from there.

Electric components like coils can test fine when cold but have a higher resistance when hot which lends to erratic performance.
 
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Old 04-22-19, 06:31 AM
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Different engine I understand, but when one of the coils on my 20 horse Kohler command went out it began acting like yours. The way I confirmed this problem was to carry a spark plug tester on the mower, and as soon as it started acting up I checked for spark. The problem with the coils when they start to go out is that heat is a factor, so if you donít catch it before it cools back down it will begin working again properly, making it harder to identify. In my case, due to the configuration of the engine in the mower, it is about a half day job just to get to the coils, and then another half day to get the engine lowered back in place and all the attachments connected, so I replaced both while I was in there. But if yours is easier to get to, you will probably want to be sure which one is bad and replace just it.
 
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Old 04-22-19, 10:27 AM
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Being that it occurs going up and down hills mostly, I would say there is water and/or trash int he carburetor bowl. When water builds up in the bowl just a little, not quite enough to reach the jet, it will still run with little to no difference, but when you tilt the engine, the water level changes and can get up to the jet. The water has much more surface tension and doesn't suck up into the carb well, it mostly just blocks off the jet, which causes a sudden erratic lean condition. Trash and sediment in the bowl can also behave the same way. I'd drop the bowl and clean it out.
 
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Old 04-23-19, 01:45 PM
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Thanks for the feedback everyone.

marbobj, your statement is correct. The thing ran perfect until I put it away for winter, then on first start this year it encountered this problem. It is definitely an incline + engaged blade related problem. And upon closer introspection regarding the SeaFoam, I was probably projecting what I wanted, instead of being objective. Post SeaFoam it runs well, but it was also only in my driveway, which has no slope. So in reality, the SeaFoam cleaned it up, but I guess I can't say it eliminated the problem. I didn't truly run it engaged over inclines after the SeaFoam, and I drove it back to the barn without the blades engaged, which is never really a problem.

I'll get the carb bowl cleaned out here in the next night or two. I'm all about checking off the boxes, and that's certainly one I hadn't considered.

And lastly, I went ahead and bought replacement coils. It's a pretty big obstacle for me to not have the mower. And the $70 they cost is easily overcome by the added impact of not being able to mow. So I'll do the coils and bowl at different times so that I can differentiate.

Thanks again, everyone. I'll be back once I have more results.
 
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Old 04-24-19, 09:13 AM
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Change one, try it out, if good your done.

If still running bad, swap it and see what happens.

You may not need both and then your have a spare!
 
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Old 04-26-19, 08:21 PM
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Well. This is disappointing.

Carb bowl is cleaned out. It wasn't dirty and there didn't appear to be alternate fluids in there. Regardless, no impact.

And with both coils changes there is no impact. Still does the same thing.

What does everyone think, plugs?
 
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Old 04-26-19, 11:18 PM
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Still probably something to do with the carb if inclines truly affect it. Depending on which carb you have, you may have the one with the formed o-ring gasket above the pickup tubes in the carb. This often gets distorted out of shape from ethanol in fuel and causes strange problems. Definitely change the plugs if you haven't already, it's too easy to do and Kawasakis come with NGK plugs and they often do strange things when they fail.
 
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Old 04-27-19, 05:57 AM
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Will do on the plugs, thank you.

I have a DS07 series FR691V so this should be my carb;
https://www.jackssmallengines.com/ja...91v/carburetor

Which one are you speaking of? Kawasaki appears to not make rebuild kits. Do you know which other consumables I should replace if I'm pulling it off?
 
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Old 04-27-19, 06:11 AM
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Are you saying this is only happening on inclines down hill as well as up hill? The engine runs well on somewhat flat mowing - no backfiring?
 
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Old 04-27-19, 06:36 AM
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Correct. Perfectly flat mowing, absolutely no issues. No backfire, no hesitation, nothing bad at all. With blade engaged, up and down hills is a problem. And just to say it again, hills are fine as long as the blade isn't engaged. So if I'm just moving it around the yard, then I can take the inclines just fine.
 
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Old 04-27-19, 07:10 AM
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OK. It apparently isn't a load threshold issue since you have the problem going downhill. With that in mind it's odd you can do inclines without the blades engaged, which in itself is loading.
 
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Old 05-01-19, 07:16 PM
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Alright everyone. Is this a cause or a symptom? It's hard to get proper lighting for these pics, but I think they came across decently. One of them definitely has more oil on it, and it's definitely darker. The one is still "white," and the other looks darker (is burnt the right word here?).

Also, the carb was immaculate. No gunk, no goop, everything was free, all jet passages were free. I went and ahead and cleaned it because I was there but I'd be really surprised if that was the cause of anything. Plugs are still out because it's pitch black and I'm not getting on it to mow in pitch black thunderstorms, but I'll try to see if I can get two plugs tomorrow and run it.

This is getting frustrating. I'm probably going to grab the compression tester while I'm at the auto store tomorrow. At least see if my cylinders are the same. I don't have the fuel pump in front of me right now, what's the proper way to cut power to it so I can crank the engine? I assume there's an electrical connector on it?

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Old 05-01-19, 10:07 PM
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The plugs look fine, the lighter one may be running leaner and hotter but not alarmingly so.

The fuel pump doesn't care if it's inclined or not. Things that could be affected by being tilted would be fuel in the carb, oil in the sump (if this engine has a low oil shutdown), and the position of your weight on the seat switch. How heavy are you and are you sitting squarely in the seat? Might try taking that switch out and strapping it in the "occupied" position and take it for a test run to see if that changes anything.

That carburetor is not the one I was referring to that gives trouble with the formed O-ring. Some Kawis have it, some don't.
 
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Old 05-02-19, 04:59 AM
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Thanks, Cheese. I should have clarified, I was asking about the fuel pump because I was going to check compression. So I wanted to turn off the fuel supply to check that.

I'm 5'11" 195 and I'm definitely sitting squarely on the seat. But you raise a good point about that sensor. I need to start thinking outside the box because the "usual" stuff isn't helping me here. I'll tinker with that switch today if it stops raining.
 
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Old 05-02-19, 06:47 AM
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The backfiring is through the intake or exhaust? And when it backfires is the performance of the engine noticeably affected?

Have you tried to isolate the problem on one side or the other by pulling plug wires or disconnecting the kill wires from the coils? I'm not finding an igniter for that engine.
 

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Old 05-02-19, 07:17 AM
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The backfiring is through the intake or exhaust? And when it backfires is the performance of the engine noticeably affected?
-I suppose, if I had to guess, I would say it's through the intake. Though admittedly it's kind of hard to put my head by one or the other while driving. And performance goes into the crapper. Completely bogs itself down.

Have you tried to isolate the problem on one side or the other by pulling plug wires or disconnecting the kill wires from the coils? I'm not finding an igniter for that engine.
-I'll try pulling plug wires tonight to isolate, I have not done that yet.
 
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Old 05-02-19, 10:19 AM
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I would also try pulling the kill wires at the coils and see if that makes a difference. If there isn't an igniter it should run. Pulling those wires isolates the ignition from the safety circuits. Keep in mind you would have to choke the engine to kill it and this is only for diagnostics.
 
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Old 05-02-19, 01:43 PM
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Choke it to kill it? Does turning the key off not work if the safety mechanisms are bypassed?
 
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Old 05-02-19, 03:15 PM
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Correct the key will not kill the engine when the kill wires are disconnected from the coils. An igniter in the circuit changes things a little as far as the diagnostics it helps with.

In checking the IPL s on that engine an igniter doesn't show. I'm only finding the coils for the ignition.

We'll have to kick that one upstairs to Cheese. He's worked on about everything.
 
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Old 05-02-19, 05:02 PM
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If you have a fuel shutoff solenoid on the bottom of the carb, turning the key off should kill it. Kawasaki quit using igniters a good while back, so they aren't a factor on these V-twins. If the solenoid is stuck and won't turn the engine off, you can choke it and if it still keeps puttering, you can pop the plug wires off with a long handled screwdriver.
 
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Old 05-07-19, 06:20 AM
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This thing keeps finding ways to irritate me.

So I cleaned the carb. Put everything back together and it ran like a champ. All misfires were gone. Mowed for around 30 minutes, so more than enough time for it to screw up if it was going to screw up. Put it back in the barn. Ran it again two days later and the misfires were back with a vengeance. So I guess I'm really onboard that I have a carb problem.

I cleaned it with brake cleaner and carb cleaner. Do I need to do something else? Do I need to find an ultrasonic cleaner? I'm cleaning the main jet, right? Carbs aren't some magically complicated thing, right?
 
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Old 05-07-19, 07:44 AM
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Cheese brought up the fuel solenoid. Does it move freely and the power wire fitted tightly? That's usually an all off or on thing. There shouldn't be anything in between.
 
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Old 05-07-19, 10:37 AM
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Have we beat to death the seat sensor?

For a long time my mower would backfire when I went from level ground down a hill, usually at a higher speed. It was not really noticeable to me but when the mower tilted down quickly, momentum kept my weight in the air long enough for the spark to stop sparking, even though it appeared to me my behind was still on the seat. Who knows, maybe 4 or 5 revolutions might go by, before my weight came back down. Enough for the unburnt gas to shoot into the exhaust and backfire. Because the engine's momentum was there the mower re-fired when my weight hit the seat again and I had no idea why it would backfire, going down hills.
Now I know.

I can run my mower, without me on the seat, as long as the blade is not engaged. So when you say this happens on hills and NOT when the blade is not engaged, it sure sounds like a seat sensor problem to me. Perhaps there is a way to disconnect that sensor so you can test out the theory.
 
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Old 05-07-19, 01:45 PM
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That's interesting, Optsy. Cheese brought that up a few posts ago. He could pull the kill wires to isolate the ignition from the safety stuff. He may have tried that. Haven't heard back yet.
 
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Old 05-07-19, 06:10 PM
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First off, the fuel solenoid wire fits properly and is clean/free from interference. I think it's ok, but as this post shows, who the heck knows.

So help me out on the seat kill switch. I pulled it out tonight and clamped it closed. It ran a lot better, but still choked down probably 3-4 times over 30 minutes. That is still infinitely better than the last time. But I suspect that's not what you guys are asking me to do. What specific wires do I want to unplug/remove to effectively eliminate the kill switch? My switch harness goes up to my ignition but it's sharing a wire wrap with other wires. I'm not entirely confident I know which two came from the switch.
 
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Old 05-08-19, 12:15 AM
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Clamping it down should be sufficient, provided the switch itself is good and the wires are. The fact that it ran much better is a good sign, and bogging down is different from backfiring, right? I would attribute bogging down to carburetor issues and backfiring to light pressure on the seat switch, given the results of this test, if I'm interpreting the information correctly.
 
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Old 05-08-19, 01:20 AM
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You can just pull the connector at the seat switch and put a jumper wire between the terminals, it's a NO switch!
 
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Old 05-08-19, 05:13 AM
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Sorry Cheese, I need to stop jumping around with terminology. It was still backfiring with it clamped down. It bogs down after it backfires while the engine is trying to catch itself back up.
 
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Old 05-09-19, 04:55 AM
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Leading into it with a backfire affecting performance that much is likely through the carburetor. It would reverse the air flow and clear the main jet of fuel. All that would create a lag to recover from and that's what you're describing.

What specific wires do I want to unplug/remove to effectively eliminate the kill switch?
The two small wires at the coils you swapped out. It has to be done at the coils.
 
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Old 05-09-19, 09:55 AM
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I can't say how much performance loss his lawn tractor experienced, but in my case, I seem to remember the mower chugging a bit before it recovered from the backfire, which in my case was in the exhaust.

Knowing now that it was all due to a very short time period of lost spark, when my seat sensor killed the spark temporarily, I now know that those lost power strokes is what made the mower chug a little, until the spark was regained.

I know my problem was the seat sensor because all I do now is hold onto the bucking bull (lawn tractor) a little more securely and make sure my weight stays planted on the seat, and since then, I have never had the issue repeat itself.
 
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Old 08-16-19, 06:04 PM
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Well. It's better?! I think my journey is complete and I'm ultimately going with dirty carb. I had it cleaned up and running a little better, then didn't mow all of July and it came back. So for the last three weeks I've been vigorously running it (ie-racking up the hours) with Seafoam fuel additive. It's running very well now and it sounds great. So I think I just didn't prep well last winter and I paid for it for many moons. Lesson learned for the next few months.

Thanks for all the help guys and gals, I really appreciate it.
 
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Old 08-07-20, 06:54 PM
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16 months later I come with my tail between my legs. About 6 weeks ago the thing went in the absolute crapper. It came back from the winter break just fine and ran well and then mid-June apparently my engine caught COVID. I actually found myself having a beverage and trying to weigh the pros/cons of insurance fraud if I got caught by "accidentally" allowing my mower to get hit by a semi.

Anything that even remotely called itself an incline sent me into fits of rage. No amount of carb cleaning resolved it. Just atrocious. Awful. Worst conditions imaginable, to quote Owen Wilson.

So I came back to this thread, looked at everything I had replaced and what we had glossed over. Spark plugs. Ever mother loving spark plugs. I replaced both and it's a brand new mower. $8.29 for 2 new Champions. Christ alive. I was so mad I still wanted to commit insurance fraud, but then I realized I love having a brand new mower back. Why in the name of whatever it is you pray to would the incline cause spark plug problems?
 
 

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