Kohler Command 12.5 - blowing lots of oil & smoke and making very loud hammering

rickpaulos · Apr 2, 2025

Rocky J said:
That does sound like the gas tank drained into the crankcase. Possibly the noise is fuel igniting in the exhaust. . You have our interest so keep us informed.

DING DING DING, We have a winner. Thank you Rocky J.

Now that it's warm enough outside to work on it. I spotted some fluid under the front left of the mower as I pushed it back out side. Right below the carb. First up, drain the crank case and about 1 gallon of gas & oil came out.
This is the first time I've even heard of that happening in any small motor.

I'm assuming it's the float needle that leaked. On this carb the needle does not have the rubber tip, there is a sea green seal in the top of the needle port. I'll be looking for a carb kit with that type of seal. I assume it's just pressed in. Float bowl gasket is rather hard.

Will clean up the carb, add new oil and try it....

Walbro LMK12798 1205301 There are some other numbers that probably don't matter.

Not finding a LMK12798 or is that model "LMK" with a date after it? This Cub is listed as 1989 to 1991 on TractorData dot com
I bought this new in October 1990 - end of season sale. So maybe a typo on the carb date. 98 vs 89.

Gezze there are countless carb kids. Gravity feed. Would need carb-to-block gasket & carb-to-air-filter gasket, float bowl rim gasket, needle, seat.

The jet is slightly off center. Looks like it's pressed in. I'll just try to bend it back.

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Cub.Cadet.Carb.Walbro.1205301.LMK12798 (5).JPG

rickpaulos · Apr 2, 2025

Carb cleaned and reassembled. New oil and filter. Cleaned the spark plug. I did try to straighten out the jet but it just springs back to where it is. Didn't want to risk breaking it off or breaking off the tool inside it. (dental pick)
Started right up and sounds fine. Blew lots of smoke as stated. Let it warm up for a couple minutes then mowed off the pampas grass. Smoked a lot for about 10 minutes then quit smoking. Ran fine for the 30 minutes I used it.

Need to get a carb kit if I can figure out which it needs. I'll change the oil again when that kit arrives.
I plan on adding a shut off valve to the fuel line.

kbowley · Apr 3, 2025

You can look up the carb via the engine model and spec (link to parts here). To get the seat out, blow compressed air into the fuel inlet and hold your finger very slightly away from the hole to catch it. Use the reverse side of the needle jet to press the new one in. If it is gravity-fed, the carb kit part number is Kohler 12 757 01-S. If it has a fuel pump, the kit is part number Kohler 12 757 03-S

kbowley · Apr 4, 2025

rickpaulos said:
Carb cleaned and reassembled. New oil and filter. Cleaned the spark plug. I did try to straighten out the jet but it just springs back to where it is. Didn't want to risk breaking it off or breaking off the tool inside it. (dental pick)
Started right up and sounds fine. Blew lots of smoke as stated. Let it warm up for a couple minutes then mowed off the pampas grass. Smoked a lot for about 10 minutes then quit smoking. Ran fine for the 30 minutes I used it.

Need to get a carb kit if I can figure out which it needs. I'll change the oil again when that kit arrives.
I plan on adding a shut off valve to the fuel line.

View attachment 70729

Looks like you're putting the old girl to work! Tough machines for what they were. I have a 1989 Wheel Horse 212-H with 3200 hours on it, and the thing won't die no matter what I do to it. The old Briggs 12 hp flathead rattles like heck but has for 15 years. I bought a replacement engine for it back in 2012, as I thought it wasn't long for the world, but I put about 40 hours a year on it, and it just won't die! Tranny is a beastly Eaton 750, and it doesn't have enough power to ever hurt it. Love old machines. Some of the new stuff I get in the shop is just sad...grab the rear fender to slide it or push it, and it bends like a piece of solder.

rickpaulos · Apr 14, 2025

Carb kit finally arrived. Shipped from California, made a side detour from Des Moines to Milwaukee and back to Des Moines then on to my town.

The kit came with 2 needles and 2 seats. The larger needle is pretty much identical to the oem but see the photos for the tip. The oem was much smoother at the tip so I put that back in. The needles look like they have lots of chromium. I can see in the photos grinder marks on the new one prior to chrome plating. The seats, well one was too small, just fell in the hole and fell right back out. The other was over sized, too thick and the hole in the middle was smaller than a hair. like .0001. I don't think enough gas could have gotten through to keep the engine going. I tried to enlarge the hold and ruined it. Put the oem seat back in. The minimal instructions say to use one gasket with certain marks on it for carbs after a certain date code. How to decode that?

I did replace the full gas line, filter, added a shut off valve and some new clips.

Changed the oil again. Filled the gas tank with gas.

Ready, crank crank crank crank crank. Would not start after some 30 seconds of cranking. Pulled the plug, clean and dry. Pulled the carb bowl, no gas. removed the filter and valve, no gas. Put a rubber squeeze bulb in the filler and squeezed several times, no gas came out. Siphoned the tank empty and removed the tank. Turns out I pinched the new gas line under the tank where you can't see. Reassembled and it started right up. Mowed some leaves and put it away. I shut the gas valve off and it takes about 20 seconds to suck the carb dry and stall out. I've always done that with other equipment with shut off valves and usually don't have problems with them sitting for long terms.