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Terry_Hart

Kohler Backfires at shut down

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Terry_Hart
Question for the Kohler experts out there. My ch18 backfired today when I shut it down, even at mid-throttle? It was doing that this summer when I shut it down at lower throttle settings.

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Burntime
My kt17 does it. Too many times and you end up replacing gaskets... Idle it down for 30 second to a minute and it does fine. If the airclean is really dirty its like running the choke on and it does it worse...just a heads up...

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Burntime
my 16single kohler does it as well and it has tons of compression...dunno, the carb is rebuilt on my kt17 and it still does it...just the nature of the beast I guess...

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D-17_Dave
A lean condition leads to hotter combustion chamber temps and red hot carbon deposits on the valves. Also hard working engine under load then shut right down can do the same thing. Due to throttle position reflecting the amount of fuel being used against how much air flow the cooling fan pushes, it's recomended that engines be ran at or near wide open throttle to cool them down before shutting off. This is how I recall Al Eden describe it. Now some engines are more prone to this I think most of this can be solved with a main mixture of near as rich as can be ran while maintaining a clean burn. I know the push is for fuel economy but these engines are cooled inside the combustion chamber with the cool, fresh intake charge. This IMO leads to longer internal engine life. Also I think Al descibed the butterfly being held shut when you idle an engine before shut down. This doesn't allow the butterfly to open when the rpm's die down. This causes a lean condition which will promote the hot carbon to light off the exhaust. Just some info to ponder.

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blackfarms1
I have a sunstar with the ch20. It has an anti-backfire solenoid located at rear of carb. Anyway owner's manual clearly states to shut the engine down at 3/4 to full throttle to prevent damage to head gasket. Sean

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Terry_Hart
I have been shutting it down at about 1/2 throttle where it says start/stop on the dash. I guess I could look make it run a little richer. Would that be turning the screw out?

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D-17_Dave
Terry, turningthe mixture screw out will richen the mixture. You'll get the best results under load at wide open throttle. You don't want to see any sputter or black smoke, and the govn. should be responcsive and crisp. You'll find that if you go to far, then turn it back in till it clears up that's where I like to set mine. The key here on this topic is finding what combination works for your engine application. Most of us when were busy don't have the time to cool down for long periods so at least inducing a little fresh, cool air helps before killing the engine.

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Cvans
I know this is a Kohler your having problems with but My Briggs was doing the same thing. After reading the owners manual, They state and I think they are correct, Raw fuel in the exhaust system is the cause of these backfires. We used to turn the key of on our old jelopies when we were kids, coast down the road a hundred feet and turn the key back on. The blast that followed was incredable. Anyway after I started idling Briggs way down before shutting it down I have not had anymore problems. This allows the exhaust system to cool down below combustion temps and the low idle reduces the amount of raw fuel pumped into the exhaust after the ignition is shut off. It doesn't cost anything to try it. Good luck, Chris

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Mike
I may be wrong but I think the 3/4 throttle shut off is for engines with the fuel shut off solenoid. I run my single kohlers for a few minutes after hard use to cool down the engine then shut off at low throttle, and it works well.

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RayS
Is the CH 18 a command with a fuel shut off solenoid? If so it needs to be shut off at 3/4 to wide open throttle. I had this problem with my Kohler Command CV20. I was shutting it off at idle when I first got it new. Manual states to shut off engine at 3/4 to WTO. It would backfire when shutting down at a idle and blew one of the head gaskets. After giving the dealer $300.00 and now shutting off at WOT it doesn`t backfire any more. Thing is I read this in operators manual and it just didn`t sound right because I always idle down my single cylinder Briggs and never had a problem. Not saying this is your problem. Just stating what had happened to me a few years ago. Wonder if it is the problem and that it may be causing your hard starting issue. Can you check compression to see if they are the same?

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cwm1276
I did not blow a head gasket, but I think the manifold gasket, the one right in the "V" of the engine under the carb. I was told the reason was the backfire as described here. Since then I shut it down at 3/4 trottle and have not had a backfire since.

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RayS
quote:
Originally posted by Storm7012
Gee, I never have that problem with my Briggs.:D
I never have either. The dealer told me that they changed the design of the head gasket some time after I bought mine beacause they were having problems with the gasket.

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cwm1276
quote:
Originally posted by sammiefish
quote:
Originally posted by cwm1276
the manifold gasket, the one right in the "V" of the engine under the carb
Im not following...
At home now, found the service manual it is the breather cover. It is on top of the engine right between the 2 Cylinders. the gasket for that cover blew out for me. Was really an easy job, just scared me when it happened and oil started squirting out toward the muffler.

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Terry_Hart
I called the dealer today. They told me to idle it way down and let it run for a few mins. I tried it tonight, started it and let it run for awhile, idled it way down and shut it off. No problems. I did it several times, but there had been no load on the engine. Will try it again next time I use it.

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