Cub Cadet 1862 w/kohler M18 , HIgh RPMs
 

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......

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

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

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....

[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...

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..... :Unknown:

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....

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?

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.

I can manually back the rpms down,,,so you think that means my throttle plate is whacky? How else can i verify this? When I cleaned carb, it seemed everything was in order inside....I may have missed something though....ugh...

My thought is that if the throttle plate were loose the air flow would tend to close it. I guess let's start with the basics. There should be a spring from the throttle cable arm to the governor arm which pulls on the governor when you move the throttle lever up. There should also be a solid linkage from the other side of the governor arm to the throttle plate arm on the carb. When the engine turns, the governor arm closes the throttle plate on the carb working against the force of the spring from the throttle cable. At WOT with no load, the throttle plate should probably only be about a 1/3 of the way open, if that.

The question then is, when the engine revs up in the manner you describe, is the governor still doing its job and pulling on the throttle spring to keep the throttle plate on the carb mostly closed, or does it give in to the tension on the spring and let the throttle plate go wide open?

The first one I found with the gov gear out acted just like this. It is simple to check the gear. Unscrew the oil fill tube from the block and you can see the gear. Rotate the engine by hand and you can watch the gear rotate and check both weights. The weights should be free a will make a clicking sound as they fall open when the gear turns. If everything looks ok then check the gov linkage. With the engine running you should be able to feel resistance in the arm as the weights spin out they push on the arm. If no pressure then something is sticking or the gov arm is out of adjustment.

Well, I can barely see them but it seems like they are not opening....but wouldnt they open when centrifugal force was applied during engine rotation while running and not just open freely when turned by hand? Either way I hear no clicking from them and from the little i can see of them, doesnt seem they are opening when rotating engine flywheel by hand. IF they were in fact defective why would they wait until the machine warmed up to act up?? It runs great for 5 to 10 minutes when first starting until it warms up.....My biggest issue now is what to do about my customer...He brought it in with this problem, but the day after it came to my shop the ignition module went out and I had remove the entire engine just to do that job and it has since been put back on mower...I doubt he is going to want to spend the extra money to have the entire engine removed again, broke down, governor replaced at this point...Especiall being over 300 into it already...Not sure how to handle billing him...Charge him for the module job and tell him he is stuck with his original problem, but over 300 dollars poorer too....ugh....This is the first machine ever I have not been able to fix....Any thoughts on governor, and customer issue? I am so frustrated.....

Your a shop??
My free advice just ended. I'll send a bill for any more advice I give.:bash2:

lol,,,I do a little part time work from my home since I raise my son at home 24/7.....Mostly for friends and old customers....but i am charging this guy yes...he is old customer....especially for the size of job I have been doing on his cub....I have exausted all resources and was trying to find a little assistance here...if you cant help a guy out without charging for the advice that is fine...But no i am not an open shop, and not open to general public....

On the governor, it will have to be replaced. That includes a complete tear down of the engine as you may already know. I don't think the engine is worth what you're going to charge him for the labor.

On the customer, I think the problem should have been properly diagnosed before putting time and parts into the engine. Easy to say, I know, but it is what it is, and the customer shouldn't be penalized. I'd say if the customer agrees to the tear down, don't bill for the first engine removal, just the coil. If they do not, decide if it's worth taking it out again to remove your brand new coil out of the engine.

I think the answer to this question will put you on the right track.

I had an M 18 where the governor backed out of the crankcase. Totally broke the governor. You could still control engine rpm with the hand throttle, all the way from idle speed to way too fast.

Well I did properly diagnose no run problem, and couldnt adress the other gov problem until that was solved. I didnt want to go to the most expensive fix fromt he get go...I figured it was either getting too much air from a leak or crack or carb issue..and couldnt rule them out until it could run .....I have never run into a governor that showed issues after warm up...from my experience they either worked or didnt work...never took warming up to go haywire....this is a first for me...I am just gong to ask him what he wants to do,,,,proceed , IMO not worth it, or leave it as is....I am sure he could sell the mower for a decent chunk even with this issue........And he can put that towards new or used machine for himself...thanks everyone...

Lets not get ahead of ourselves. The procedure I gave you was just to make sure the gov was intact. If the weights are not swinging free then maybe the shaft is out of adjustment and the are is putting pressure on the button that works in and out when the weights are spinning. As for rpm changing after it warms up that could just be metal expanding as the temps go up.
The main thing is the governor gear and weights are still in place.

Have you ever been inside one of these engines to know how all these parts work together? If not I can send you a pic but it will have to be through email. My computer is down and I have no idea how to upload pics from this phone to the site.

Down load the manual, read the manual then decide if you wish to repair it.

http://www.onlycubcadets.net/forum/s...ead.php?t=4648

If it has not tossed a rod out the side of the case what have you got to loose?

You may be able to fix it for cheap $$ if it's toast, Oh well life goes on.

Going by the way he said the gov weights acted My bet is the adjustment is all wrong. The weights should fall free when rotated and if the lever is pressing on the button there is no way the weights can swing out and work.