kohler cv12.5s-1270 small engine

14 years ago

I have a stx38 john deere with a kohler cv12.5s-1270 engine. It seems to be having some trouble. It is very hard to start have to full choke it several times before it will finally start then after starting it is running very rough almost like it is surging up and down. I have tried adjusting the idle screws with no success. I just think something is wrong because it isn't running right at all. I can't find very much information about it at. Does it have a fuel pump? I cleaned the carb the best I know how ,first time cleaning a kohler have cleaned several B&S. Any suggestions would be very appreciated. Things I have already tried.

Cleaned the carb.

Installed new spark plug

Changed oil and filter

Installed new fuel filter

Installed new air filter

Drained gas tank and filled up with fresh gas.

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Comments (7)

rcmoser
14 years ago
Coil or coil wire probably going bad, when it acts up pull the plug and connect it to the spark plug wire and ground it against the engine. crank it over and see it you got a nice pretty blue spark?
rcbe
14 years ago
and if you left old gas sit up in the machine for a decent period of time (>1 month), there's a good chance that your engine's carb is partially blocked up with gelled fuel residue or other trash. Such will call for removing then tearing down carb, cleaning it thoroughly, putting in a new carb kit and back up on the engine...
walt2002
14 years ago
Sounds to me like blockage in the carb.

I think you can download a manual here.

http://www.mymowerparts.com/pdf/

Walt Conner
tomplum
14 years ago
Along with the other guidance given, you should replace the fuel line if it is original when you clean the carb. The other basics would be to ensure the vent in the fuel cap is open. Generally, you need good flow down to the carb. Yours has no fuel pump- it relies on gravity. Ignition coils on these do fail, and some times the cd in the coil that times the spark will tell it to fire at the wrong time and still have good spark. Normally starts as a hot stall though. To confirm, spray carb cleaner down the airhorn as you crank it- like a starting fluid. If it runs on that, then you're back to the fuel system. The battery ground cable on yours I think is attached to an engine mounting bolt on the RH side. I've had a couple give me fits as they didn't have a good ground at the frame anymore. If yours has a fuel solenoid below the carb, it needs- I think 10+ volts while cranking and a good ground to function. these plungers also get sticky from sitting.
sstaceyswims
Original Author
14 years ago
Ordered new coil and carb rebuild kit today. Will post results in a couple days.
sstaceyswims
Original Author
14 years ago
After spending 75 dollars on parts it turns out it was a 2 dollar key. The flywheel key was sheared just enough to put it out of time. Thanks for all the info you guys supplied. At least I have a rebuilt carb. new coil, plug, air filter and some new knowledge.
rcmoser
14 years ago
75 bucks would of been 1 hour of labor at the repair shop, not to mention the mark up on parts. So looked what you've got for your 75 dollar investment. A new coil, clean carb. tuned up, and the ability to actually find and fix the problem. IMO priceless, not to mention the kolher will run good for another 10 years if you change the oil two or better three times a year.