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Old 07-20-2011, 06:41 PM   #1
mufflerbearing
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Angry Kawasaki FB460V hunts/misses/backfires.

Hey guys, got a real tough one here. I got a free John Deere SX95 riding mower a few years ago. It was non running and needed a lot of work. Well, long story short both the ignition coil and igniter were bad and needed replacing. I priced the parts out from both John Deere and Kawasaki and the prices were absurd for both parts(like $60 for the igniter and $80 for the coil). I ended up going with aftermarket units for less than half the price which seem to work fine. When I first got it running, it ran nice and smoooth. Idled perfect too.

All of a sudden, it started to rev up and down, backfire, and misfire no matter where you put the throttle. It will not idle for anything. The only thing that made it better was if you choke it slightly and it would smooth right out.

Cleaned the carb(several times), changed the plug(gapped it), decarboned the head, tried fresh gas, bypassed the fuel tank, checked the fuel pump,and replaced the air filter with no luck.

BUT when I engage the mower deck, the engine smooths right out. It runs fine under load, but when its not under load, it runs like crap. The worst part is now it is drinking gas at an alarming rate. I only have around 2 acres to cut and by the time I am done, the tank is almost dry. I would guess the tank is a good 1.5 gallons or so. That is a heck of a lot of gas to cut my grass. At 4.XX a gallon, it gets expensive quick if you are cutting your grass 1-2 times a week.

I am pretty much at loss what the problem could be. I love this machine but it is just driving me crazy. I know its not supposed to run like that.

Any thoughts?

Thanks in advance for any advice.
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Old 07-20-2011, 06:57 PM   #2
WNYTractorTinkerer
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Icon2 Re: Kawasaki FB460V hunts/misses/backfires.

So it's drinking a lot of fuel?
Runs OK @ WOT with load on?

Sounds like it's richer that all get-go..

Post a picture of your bald head (from the scratching)!!

Troubleshoot the thing as if you haven't done any of the listed work (start again)

Plugs,
Compression,
check spark,
How is the voltage while the thing runs? Is it high as heck?? Does it come down to normal levels when PTO is on?
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Old 07-20-2011, 09:00 PM   #3
rscurtis
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Default Re: Kawasaki FB460V hunts/misses/backfires.

What you describe generally means a clogged idle jet. You don't have to remove the carb to clean it, just remove the air filter base. You'll see a screw on top of the carb. with a hole in it. Remove it and clean the orifice in the bottom, it's very small. When you re-install the air filter base, be sure the breather hose is connected, or you'll be sucking dust.

If your compression feels low, you may have lost intake valve clearance, a common issue on this engine. It will also result in poor running. An absolutely clean air filter is also essential on this engine.
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Old 07-22-2011, 06:15 AM   #4
Oldphil
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Another thing to check is idle speed, I have run onto a few that bounced on the governor due to the idle being set to high. The would pop during the up down cycle.
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Old 07-22-2011, 11:12 AM   #5
mufflerbearing
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Quote:
Originally Posted by rscurtis View Post
What you describe generally means a clogged idle jet. You don't have to remove the carb to clean it, just remove the air filter base. You'll see a screw on top of the carb. with a hole in it. Remove it and clean the orifice in the bottom, it's very small. When you re-install the air filter base, be sure the breather hose is connected, or you'll be sucking dust.

If your compression feels low, you may have lost intake valve clearance, a common issue on this engine. It will also result in poor running. An absolutely clean air filter is also essential on this engine.
I'll have to give that a shot! I cleaned out the carb several times but I don't think I touched the idle jet.

I was also thinking bad valve clearances as well. That is another thing I haven't checked yet. Compression seems pretty good though. I had the head off and the cylinder looked like brand new. You can still see the cross hatch in it!
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Old 07-24-2011, 08:27 AM   #6
mufflerbearing
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Well, yesterday and went to find that low speed jet on the carb. I ended up taking the carb back off(big pain on a SX95 BTW) and saw a screw on the top with a little bracket. Tried to take it out and it stripped out(Phillips head). So I grabbed my vice grips, grabbed the screw and broke it loose. Pulled the tiny Jet out and oh my gosh, the thing was plugged up solid! Cleaned it out really good, put it back together, and it runs like a TOP. Dead smooth like it used to run. Wouldn't idle properly because I didn't set the idle screw. Fooled around with it and got it to idle perfect now. I can't believe that I cleaned the carb 4 times and missed that screw.

Only thing left is to cut the lawn again and see if it uses less gas now. I bet it will as the exhaust smells different now.

Big thank you goes to rscurtis for the lead on the idle jet! I probably would have never figured it out! I have never seen anything like that before.

Thanks Guys!
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Old 07-26-2011, 10:31 PM   #7
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Do you think the same fix would work on a Husqvarna GTH2254XP lawn tractor with a FH641V and a Nikki carb?
The carb does not seem to have a screw on top with a hole.
It used to backfire occassionally under load and has now progressed to backfiring thru the carb most of the time.
I can post a picture of the top of the carb if you need it.
Should I start a new thread with this?
Thanks,
Dave
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Old 07-27-2011, 11:00 AM   #8
rscurtis
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Default Re: Kawasaki FB460V hunts/misses/backfires.

If that engine has a 2-barrel carb., the side that feeds the bad cylinder most likely has a clogged main or idle jet. Of course, pictures are always helpful.
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Old 07-27-2011, 07:40 PM   #9
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Hi rs,
The first issue with the tractor was that it would randomly bog down and stall for no reason. When i removed the air filter the bottom of the aluminum filter housing (for lack of a better description) had about 1/4" of gas in it. I would remove it with a syringe, restart it and continue. Later it started to backfire through the carb. It has never backfired through the exhaust and has always shut off without any run-ons. See picture of carb attached.
Thanks,
Dave
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Old 07-27-2011, 08:24 PM   #10
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Default Re: Kawasaki FB460V hunts/misses/backfires.

If you don't find any issues with the carb., then verify the engine's running on both cylinders, and if not, pull the valve cover off the dead cylinder and see what's going on.
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Old 07-27-2011, 08:35 PM   #11
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

What makes you think that one of the cylinders is bad?
Where are the jets on this?
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Old 07-28-2011, 10:05 AM   #12
rscurtis
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Remove the fuel bowl and you'll see the jets. The fuel puddling in the intake would lead me to suspect that one cylinder isn't breathing properly. If the engine runs better with one plug wire disconnected, you could have an exhaust valve not opening or a bad camshaft.
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Old 07-30-2011, 01:02 PM   #13
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

The #2 cylinders spark plug was completely black from carbon. #1 looks good.
Compression is 80psi for both cylinders. I removed both valve covers. It looks brand new. The pushrods are straight and all the valves move as they should and nothing is broken or missing. Carb looks good. I reassembled it and it starts and runs good and smooth for about 10 seconds and then dies. Is there a safety circuit that will not let you run the engine without the plastic shroud? I put my finger over the cylinder head port which is connected to the fuel pump. Does the pump run on pressure or vacuum? There seems to be both when you crank the engine, it switches back and forth, pressure vacuum, pressure vacuum.
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Old 07-30-2011, 03:59 PM   #14
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

Got it. I put the float in upside-down.
Any idea what the ignition coil air gap should be for this FH641V?
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Old 07-30-2011, 05:17 PM   #15
dstark
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Default Re: Kawasaki FB460V hunts/misses/backfires.

The tractor starts and runs good until it is at full throttle, then it starts to miss a little. When i engage the blades it starts to backfire through the carb again. Do you think it could be an electrical problem? The coil gap is approx 0.012.
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