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Jeff_B

Kohler 10hp backfiring

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Jeff_B

Need help! Had an 'interesting' problem while using my new-old horse today (1978 C-101 with Kohler 10hp, 36” rear discharge, see my posts in the 'tractor' section). I'd like to get some opinions on what it might be. First of all, it performed like a champ. My lawn was VERY high and thick (not mowed since Independence Day because my old mower had broken down). The tractor was plugging right though it, though. Generally in 2nd gear, sometimes in 1st through the heaviest stuff. It was hot out too, about 90 degrees and you could tell the tractor was working really hard. After about an hour, the engine sounded like it was laboring a little more than it had been, then it stalled. When I tried to restart it, it wouldn't catch, but would backfire as it was cranking. Finally it caught but only ran for a few seconds. When I tried to restart it again, it did the same thing, backfiring while cranking. This time it didn't seem like it was going to start so I pushed it back to the house. After an hour of cooling down, it started right up and ran perfectly. I mowed for another half hour without incident. One more thing. A couple seconds after I shut off the engine, and it's stopped altogether, it will backfire, just once. I changed (and gapped) the spark plug and changed the air filter when I got the tractor a couple days ago. Could this be an ignition problem (points, condenser, coil) or carburetor? What about that golden oldie, vapor lock? I think that single backfire upon shut down might be related. Any ideas? THANKS!

1978 Wheel Horse 8-15-15.jpeg

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Ed Kennell

May be time to pull the head and clean out the carbon check the valves, and clean all the cooling fins.

Edited by ekennell
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Wheelerspop 121

Check the oil level. My 10hp will act that way if the oil gets low. Also play with the carb settings, mine will back fire if the high idle is set off of where it likes it.

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slammer302

i would pull the head and clean the carbon out this is supposed to be done every 500hrs i think and i would also check points gap timing might be off a little 

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boovuc

I know you have  quite a few suggestions and just like a bad golf swing, you don't want to try too many at once.
But...........backfiring, running awhile then getting labored may be a sign of a too lean fuel mixture. This would make your engine run hotter than it should.

Before you decarbon the head and in the order I would do, I would increase the fuel mixture on the carb, (turning the hi speed needle out after the motor is running and warmed up). Open it up until the high speed starts to break down then turn it in enough to make it run right. After doing this, mow and see if it repeats the bad behavior.  If your fuel lines are OLD, change it and put a new fuel filter in the line. Run it with the gas cap loose or put a new gas cap on it. (Plugged cap causing a vacuum in the tank). All these can cause poor fuel delivery and a lean mix.

Make sure you check your oil level with the dipstick all the way pushed down. (Not just to the point where it needs pushed down). Use 30 weight oil in this heat and through out the summer months.
While your at it, you may want to check that spark plug you bought and see if it truly is the correct plug for that engine and not a hotter plug. (Or wrong plug period). As stated above, check your points and for the little money involved, change the condenser while your at it.

You can decarbon the engine after the mowing season is over but carbon deposits aren't the single cause of the tractor loosing power and not restarting. Carbon deposits add heat and can cause a backfiring on shutdown. It can create pre-ignition of your cylinder but not enough to create what you describe. IMHO

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Jeff_B

A little knowledge is a dangerous thing, and that's exactly what I have...so I really appreciate the advice. This is a 40-year old tractor but doesn't look like it's ever been used very hard. That's a good thing, but I suppose that can also lead to excessive carbon buildup. I would rather wait until the end of the season before I take the head off, if at all. My philosophy is to take things apart only as much as necessary. Although I realize it might be necessary. Anything special I should know about removing the head, other than cleaning the mating surfaces and using a new gasket when I reassemble? I did order a set of OEM Kohler points and condenser yesterday. I figured that if I'm going to check them, I might as well replace them, since they're probably original to the machine. The fuel lines, filter and pump were all new last year, and look good. The cap is old, I'll have check that out, but I saw plenty of gas going through the see-through filter. I'll try adjusting the carburetor, since you suggested it, but I'm generally reluctant to tinker with those adjustments on my own. I'll do that after the points and condenser are replaced (and points adjusted). I gave the auto parts store the right spark plug number, they cross-referenced it and sold me an Autolite 216. I assume that's right but I really don't know. I'll change out the oil to straight 30 weight. I assume 10w-30 is good for fall-winter-spring? I plan to use it to plow or snowblow this winter. Again thanks everyone, for taking the time to answer me. Can't promise this is my last question though!

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Ed Kennell

If you haven't already, you should go to the manuals section and print out the  manual for your tractor .  This will supply the head torque procedure , carburetor , points, plug and valve settings.
Sounds like you are  replacing both fuel and spark parts which is not a bad idea if they have never been replaced.
But my experience is it's less frustrating and less costly to  first determine which is missing , fuel or spark,  then start checking and replacing individual components if they are not performing properly.

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MikesRJ
 

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