View Full Version : kohler magnum 20 internal governor

08-14-2007, 03:59 PM
I've actually got 2 problems.
first, I have an older yazoo 3 wheeled mower with a 60" front mounted deck and had a kohler magnum 18 on it. it started running rough and died. after a few minutes, it would restart, but die again. I pulled off the air filter and tried again. after it started, it would run a few seconds and then a flood of oil/gas mixture shot up through the crankcase breather tube and flooded the engine. I pulled the dipstick and it smelled like gas. when I drained the oil, it was very thin and contained a lot of gas in the oil. One person told me that it could be the needle and seat in the carburetor. does that sound right? I had a used magnum 20 that had an unknown history out on the farm. I put that motor on the mower which brings me to my second problem.
The magnum 20 fired right up, but seemed to have an internal governor issue.
I reset the governor and it seemed to run ok at first, but after mowing for a while, it started to overrev and and it seemed like the governor was acting up again. it then blew the plug out of the front of the governor housing along with some oil. I immediately shut it down, came in and found this forum where I'm asking for some help. What could be the problems with these motors? would there be usable parts from from one motor to fix the other? (fuel pump, carburetor, etc) any suggestions would be appreciated.

08-14-2007, 04:56 PM
almost all the parts switch--should have just put a needle and seat in the 18--thats why you had gas in the crankcase--and ya--something internal to the gov is sticking

08-14-2007, 08:15 PM
A ruptured diaphragm in the fuel pump will fill the crankcase also.....

As for the 20, Sounds like a tear-down inspection is in order.

08-14-2007, 08:35 PM
if i swapped the fuel pump and carbs from the 20 to the 18, do you think this would help out the 18? could i even swap the carbs? would they be the same size? what is the difference between the two? bore, stroke, cam,? approx how much would it cost to get a needle and seat in the 18's carb? just a ballpark estimate. i really need to get this mower going. i mow about 4 acres a week with it and it's a heck of a lot faster than my wheel horse. thanks,

08-14-2007, 09:11 PM
Swapping the 20 carb and pump will only help the 18 run if they don't flood also. The pump will be the same but not sure on the carb. without ALL numbers off both engines. I wouldn't hesitate trying. A repair kit for the carb is in the $10/12 range.

08-15-2007, 10:49 AM
What plug did it blow out of the front of the governor housing? See the Kohler Service Bulletin 246 thread.

08-15-2007, 12:53 PM
ive had both carbs--and tore them apart--and can tell no diff in the jet size--or anything else-----the crank--rods, and pistons are diff between the two--the rest is the same----and as rob said--fix the carb--and check out the fuel pump for leaks--and away ya go---

08-16-2007, 09:49 AM
Are these vertical or horizontal engines? You are fortunate to have two almost identical engines. As thecrankshaft asked already, I'd like to know what exactly blew out of the 20. I have a kohler MV20 that I've been rebuilding lately myself. It's not that hard and parts are readily available in case you are interested. The SB 246 mentioned above is very relevant in this case. If you want to get a copy look up my other threads and you will see it as an attachment someone posted yesterday.

Good luck,

08-16-2007, 12:18 PM
These engines are easy to work on, but they can be time consuming, thats for sure.