Overheating K301 in a Cub 127
 

Hi all. Great info on this site.

I am in New Zealand with a Cub 127 and a Kohler K301 engine. It was a family heirloom so I threw it in the container when we shipped our belongings across. It always started very hard. A lot of turning over, and over while it slowly wound up till it started. Since it was a family gift I figured it was just old and tired. Then one day I noticed I could see right through the side of the head into the combustion and watch the blue flame inside the engine. Very strange that it still ran and even kept starting.

The other thing it was doing was overheating. I have plenty of airflow, but still, it would overheat. Of course, I never drove it less than full throttle as that was barely enough power to cut the lawn.

Anyway I just used it for a half hour or so and shut it down when it started sounding like a rod knock and piston slap was taking place, let it cool and it was good for another cut.

Then some guy down the road put up an ad for an old, old Cub. Turned out it was also a 127 like mine. What are the odds? The 127 was never imported into NZ and here in the next block in another. I figured the head might still be good so for 75 bucks I bought it and got a spare of most everything.

I pulled the head from the family tractor and found it was just a blown head gasket. I pulled the head from the old 127. The engine is very used up and I can see it has been rebuilt at least once with a noticeably larger piston. I put the old head gasket into the family Cub, started it up and it purrs. Just like that.

I found a new head gasket that is now on order. I went and cut the lawn and suddenly the engine has heaps of power and cut just great. Only after about 40min or so it again began to overheat. Same as before.

I am now trying to track down why I am overheating. I have heaps of airflow, the oil level is up. I have tried regular car 10-30, then tried oil for my little diesel engine, then I tried stationary engine oil 10-30 and it's all the same. 40min and it begins to overheat.

I am wondering if there is something internal that is loose so it slowly produces more heat than the engine can dissipate? But it sounds just fine till it overheats and then starts making all kinds of clanging noises. I shut it down, let it cool and its fine again.

I also have the engine from the second Cub. The guy told me it ran fine, but it was used to tow little trailers on the beach so the bolts are all stuck. I even broke a head bolt trying to take it apart. I am thinking of using that engine as a last resort if I can't fix the overheat but I keep thinking it must be something kind of simple?

Any ideas?

Thanks.

Scott in NZ

A "lean" carburetor will cause overheating. Try adjusting the Carb for a "richer" mixture.

Cub Cadet and Kohler both recommend an SAE-30 weight oil for the Kohler engines. The only time to use 10-W30 is when the temperature falls below 0°C (32°F) while using the engine.

I don't know how long it was run with a bad head gasket for. I would think if that is even possible you would have to adjust the carb drastically to make it run like that. Really you should have close to or 0 compression with a gaping hole in th gasket. You will certainly have to readjust carb after running that way

If it's getting hot you either have a mouse nest in the blower housing or the carb is running to lean. I would suggest getting a carb rebuild kit and giving the carb a good cleaning, download the k series service manual from this site and it will explain how to properly adjust the carb.

exhaust valve might be tightening up in the guide when it gets hot causing your problem . or a condenser or coil breaking down . did you clean the points and set them at .020 or set the timing ?

I do believe it is almost the first day of winter down under, so the oil he is using is prolly correct.
Check the timing too.

How do you know it is getting "plenty of air flow" ?

Answer: you have to pull the shrouds and inspect.
Clean out any debris, make sure the engine fins are not clogged with anything.
See that the flywheel fins are all there and that the screen on flywheel is clear.
Put all the shrouds back on and replace any that are missing.

Winter in the southern hemisphere....

Loads of other issues with the first post.... and you guys really think he may have an overheating issue? I think he has about 4 or 5 things he needs to address, and I highly doubt it's overheating. If it is, he ran it so long with major issues, it may just be done. But sure, tweak the carb. See if that fixes it. :RollEyes2:

I think your right on that as well.
Gross neglect and running it till you kill it is never any good.

Thanks
 

Hey guys, thanks for the tips.

On the airflow, I just had the head off so I had the two top cowls out and was able to inspect and get a pretty good look at the air ducts and fins. They were all very clean as was the blades on the flywheel. The second and spare unit I just bought is totally clogged up. I can also stand in front of the engine and feel the blast of hot air coming out of the front of the head. It seems to be a LOT of air for a 12hp engine.

I am also amazed the engine ran with the blown head gasket. The gap was about a half inch. Now it starts first pop and idles right down like it never did before.

I will have to check out the rich/lean prospect. That sounds like a great tip. I will download the manual and see what I can find. I am trying to wrap my head around why the wrong fuel mixture would make the engine overheat. I had better look for a forum post that explains that.

On the oil 30wt - that is why I tried the diesel engine oil. It was straight 30wt and all I could get for a stationary engine was 10-30. Still, the poor engine is 50 years old so I figure oil back then oil options were more basic so I am guessing it can't really be the oil?

One other question, I pulled off the mower deck, changed the bearings in the center shaft, sharpened the blades, and put it all back together. Now the three blades seem to be cutting at different levels. Is there an adjustment for this? It seemed the blades just sat against the cup and that did not seem to have an adjustment.

Amazing machine to still be cutting grass after 50 years.

Thanks again for the help.

scott