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Terry_Hart

Kohler Backfires at shutdown

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Terry_Hart
Hi experts! This is my second Kohler it is an Comand 18 in a Soveriegn. When I shut it down it usually backfires. Starts great runs great doesn't use oil. I let it idle down and move the throtle back to the start/stop position and shut is off. In a few seconds it backfires. Any ideas?

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Roy
Rod is correct. Shut down at at least 3/4 maximum speed to full throttle. A fuel shutoff solenoid kills the fuel to prevent backfires which can be destructive to the engine.

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cwm1276
I now shutdown my command at near full trottle. Actually rarely trottle down with it, unless I am hopping off after doing easy tasks. The engine likes the higher RPM's for cooling so I don't back off. I used to idle down and not worry about that backfire until this spring I blew the gasket at the top of the "V" under the carburator.

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dentwizz
What about lowering the rpm and doing a throttle up control motion the instant of shut-off? Produces lower coasting and still uses the solenoid function? Just curious.

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D-17_Dave
There are a couple of things that lead to back fire problems. One is a lean carb mixture and the other is carbon/oil buildup in the combustion chamber. At working temps the combustion chamber runs at or near red hot. Stopping work and shutting down at full throttle still leaves the hot spots to ignite any vapor left in the engine. The lean mixture can add to the heat in the cyl. as more gas vapor will cool the combustion chamber from the inside just as the airflow passing over the fines cools it from the outside. The cooling fan pushes more airflow over the fins at a geometric rate. Something like twice idle speed gives you 4 times the airflow and so on up to full throttle. I may be off a little in the math but you get the picture. I'd recommend either throttling down instead of shutting down if it's for a off and on situation or reduce the load, run at full throttle for 90-120 seconds, then leave it at full throttle and shut down. This should cover several possibilities. A lot of this information was provided to us by Al Eden. You might want to look up this condition under his name in the archives for a better and more factual explanation.

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RayS
quote:
Originally posted by Roy
Rod is correct. Shut down at at least 3/4 maximum speed to full throttle. A fuel shutoff solenoid kills the fuel to prevent backfires which can be destructive to the engine.
Roy is correct about the shut down and the fuel solenoid. I learned this the hard way. My owners manual states this. It didn`t seem right to me. I ended up with a blown head gasket and a $320.00 repair manual. It has been 4 years since I had the head gaket done and i shut it down the way it is suppose to be done and I haven`t had any backfiring.

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Terry_Hart
Thanks for all the info. I had heard that Kohlers like to be shut down at higher RPM. It just seems strange, I never experienced this with a Briggs. Tell me where this solenoid is. I will try shutting it down at a higher RPM.

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RayS

[img]/club2/attach/RayS/carb.jpg[/img]
The solenoid is on the bottom of the carb bowl. Some of the commands have them some don`t. If it has it, you have to shut it down at half to wide open throttle. If it does not have one then you can shut it off at idle. The old cast iron Briggs don`t have them but some of the newer ones do.

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