Cub Cadet 1862 w/kohler M18 , HIgh RPMs

Baklava · #1 08-09-2015, 12:57 PM

I have a cub 1862 with a kohler m18. Engine model# is m18s 24646 and the mower model # is 141681100 serial 814619. After ten minutes of running the rpms will skyrocket unbelievably high. And then you have to shut it down asap....Then once cool you can run it again until about 10 minutes pass and the rpms skyrocket again....I ruled out governor in my mind because its mechanical and it would not wait until warmed up to act up, at least from my knowledge and experience...so I thought maybe the carb needed a good cleaning...did that and still same problem....Could it be that when it warms up it is sucking in air somewhere into the intake? Or what are your thoughts my kind helpful people?
Thanks in advance......

J-Mech · #2 08-09-2015, 02:41 PM

Can't you just throttle it down and it will quit over-revving? Or do you have to shut it off?

timbo2 · #3 08-09-2015, 03:45 PM

could the governor arm be working loose on the cross shaft? I wouldn't think it would take 10 minutes but it's work a look

Baklava · #4 08-09-2015, 03:47 PM

Quote:

Originally Posted by J-Mech

Can't you just throttle it down and it will quit over-revving? Or do you have to shut it off?

If I have it at full thottle have to shut down right away. If I take it down to half throttle it will calm down, and you can almost get it withing acceptable running range, but if you then turn the pto on there is not enough power to run the blades....and it only over revs when it warms up about 10 minutes of running... Full throttle it over revs after warm up, half throttle after it warms up and it barely runs at acceptable RPMs...There is a big drop off int the RPMs between full and half....as in the over rev doesnt subside after you throttle down until the exact moment you hit hit throttle...there is no middle ground really...if you catch my drift....

Baklava · #5 08-09-2015, 03:50 PM

[QUOTE=timbo2;340827]could the governor arm be working loose on the cross shaft? I wouldn't think it would take 10 minutes but it's work a look[/QUO

No, I checked for that....and also thought why would it take 10 minutes...its purely mechanical....it either works or it doesnt...so it has to be something is changing once the machine warms up......it doesnt over rev gradually either...it just goes VROOOOOOOOOM up to insane , scare you, rpms...lol Was thinking maybe something with the butterflies on carb, but they didnt seem to be loose or have too much play when I checked them during the breakdown and cleaning of the carb. This is getting frustrating...

J-Mech · #6 08-09-2015, 03:56 PM

Your overlooking something incredibly obvious. The governor can't change after it's warm. Either it isn't working when it's cold and you don't notice it because the engine isn't running correctly to begin with, or you have a crack somewhere that lets in air. Problem is, it would have to be a horrific crack to make it do that. I agree, it can't be mechanical. You are missing something.....

J-Mech · #7 08-09-2015, 03:57 PM

Quote:

Originally Posted by timbo2

could the governor arm be working loose on the cross shaft? I wouldn't think it would take 10 minutes but it's work a look

That wouldn't change after it warms up. Either it works or it doesn't.

Baklava · #8 08-09-2015, 05:10 PM

Quote:

Originally Posted by J-Mech

That wouldn't change after it warms up. Either it works or it doesn't.

Yes i didnt think the governor would change after warming up...wouldnt make sense....

Baklava · #9 08-09-2015, 05:13 PM

Quote:

Originally Posted by J-Mech

Your overlooking something incredibly obvious. The governor can't change after it's warm. Either it isn't working when it's cold and you don't notice it because the engine isn't running correctly to begin with, or you have a crack somewhere that lets in air. Problem is, it would have to be a horrific crack to make it do that. I agree, it can't be mechanical. You are missing something.....

I may have found issue.....could the metal gasket between the intake and head be the issue? I was just starting it, its cold again, and sprayed some carb cleaner around the carb and anywhere feasible that would let air in...and while around the intake on the right i noticed a small increase in engine rpms, but not a crazy rev up....could this be the area that when its warm it over revs? I hope i found prob...i am replacing the gaskets tomorrow....unless anyone sees that as unwise.....any thoughts?

J-Mech · #10 08-09-2015, 06:06 PM

It's a metal jacketed gasket, but not a metal gasket if that makes sense.

Yes, it is possible..... but you still need to verify that the throttle plate/ governor is working correctly. It's not difficult to check this stuff..... With the hood off, if it over-rev's you can manually idle it back down. Unless it is a vac leak, or something in the governor is really sticking bad. Like I stated, for it to go as fast as you are talking, it would have to be one hell of a leak.