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Dave M

Engine runs too fast

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Dave M

I'm stumped. :notworthy: I tore down my 416-8 motor (Magnum 16HP) because I thought the governor had failed internally. The engine would run wide open, unrestrained, way over the safe rpm range. While inside, I replaced the piston and rings, did a valve job, and replaced many gaskets. The governor, which I thought I would find in pieces in the bottom of the oil pan was fine and functioning as described in the manual. After reassembly, I'm having the same over rev issues. I have adjusted the governor externally per the manual and I have set the high speed screw on the throttle linkage. The external governor spring looks good and I have attempted to adjust its sensitivity per the manual. I'm open to any and all suggestions. :thumbs: Thanks, because I'm getting nowhere on this otherwise pretty nice 416. Merry Christmas.

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rick

On my M series Kohler engines, there is an adjusting screw to set the governed max speed. It is mounted on the blower cover. It sets the maximum travel for the the throttle linkage. Maybe it is missing?

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wallfish

I don

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Dave M

Thanks for the replys, especially on Christmas Eve. Rick, I have tried readjusting the speed adjustment screw you are refering to, but this doesn't seem to be the issue in this case. Yes, it is there and intact. Wallfish, you bring up some interesting points and I will try to test the resistance of the governor to applied pressure as you have described. It could be that just because the governor gear and mechanism looked good at disassembly, didn't necessarily mean it was functioning properly. I also thought about something maybe in the carb causing the problem, too. As far as the history of the motor (and tractor), all was good up until a couple of years ago when it started running way over the rpm limit. And, its only when giving it throttle, not at idle. For a year or so, I just ran it at half throttle. Thanks again. Dave

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Save Old Iron

Air, fuel and spark (yes, and compression) = a running engine

a fast running engine needs lots of air and lots of fuel. The air must be coming from somewhere to support this engine speed. And since the engine is running well at high speeds, it sounds like it has the ability to mix the air with fuel properly

to me that means an air leak thru the carb !

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Dave M

I'm not sure where you are going with a "leak through the carb", old iron, but the carb is tight to the block, and the throttle shaft seems to be true. So, I don't know what other air leaks there could be, but I will continue to look for any and all remedies for this problem. I appreciate your input. BTW, I was able to "rebuild" my ignition module (see my other post on replacing HT wire on the ignition module) and it seems to be providing the necessary spark to the plug to fire this motor to life. I used a 7mm (instead of 8mm) copper core wire and glued it to the module using "Locktite Repair Extreme All Temperature" to cement the HT wire to the coil (module). So far so good on that repair. Thanks again for your help. Dave

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rickv1957

Just asking,a couple of years ago when engine RPMs started acting up,was all at once or did motor work up to that,Rick

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Save Old Iron

Dave M,

I reread your original post - do you have any control over the engine speed if the throttle is brought back to idle ? any reduction in speed ?

as far as air thru the carb - check clearance of the throttle plate to the carb bore (at all points in the circumference of the bore )- at idle, no air should get past the throttle plate at the bore wall. also check the "looseness" of the carb throttle shaft in the carb body - both side to side and up and down - wear at the shaft to body junction can act like an open throttle plate - still allowing for a good air fuel mixture to leave the carb body into the engine.

Maybe I can sneak a few pics of the throttle area on my 416-8. Its apart right now for "refreshing" but the cables , springs, etc may be intact enough to give you a visual comparison of where everything goes.

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Dave M

Maybe its time for a little confession here. :thumbs: When this high rpm started a few years ago, I had revved the engine at the carb using my thumb to push the throttle open. This was a very momentary rev, the kind of thing where you tell yourself you're "blowing out the carbon" or the "cobwebs" etc. (Bless me Father, for I have sinned?) Anyway, it was after that incident that things started going downhill. I also have a 310-8, same Magnum motor configuration, which I also just rebuilt due to an oil burning issue, replacing the piston/rings/rod. I believe there may have been an occasion when I had done the same thing (revving the engine, briefly) to the 310. Anyway, on the 416, along with my momentary loss of good sense :notworthy: when I revved the motor, I figured I probably toasted the governor gear. But, in the teardown, the gov gear and flyweights and pin all looked good. This is why I'm looking for other external possibilities. For my pennance, I'm thinking I'm going to go back in and replace the governor gear, something I should have done when I was in there the first time. And, I do have control over the engine speed using the throttle. It does idle well. Thanks. Dave

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rickv1957

Dave,I cant help but think your problem is exteral,is govener arm adjusted correctly on shaft ,on the K series engines that adjustment was the anwser to your problem,Rick

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Dave M

Rick, I have adjusted the external governor arm per the Kohler manual. I am assuming that rotating the governor shaft counterclockwise means as viewed from the front of the tractor. I have set the governor spring sensitivity to its original setting as well as up and down the spectrum of holes in the governor arm. Dave

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rickv1957

Dave,with throttle at idle,did you try opening up arm a little like John sugguesed to see if govener pushes back,Rick

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Dave M

It's kinda cold in the shop, but I looked at the situation today, anyway. I took the external governor arm off, and wanted to see if the governor shaft moved when I raised the rpm of the motor. It did move, so I figure the internal parts of the governor may be okay. I reinstalled the governor arm and adjusted it yet again per the manual. From there I went to the throttle cable and then to the high speed screw on the blower housing adjusting each one in turn, engine running. While it dosen't seem to be up to the 3400-3600 rpm (I have no tach) that it should be, it looks like the governor is working at intermmediate speeds and it's also not wanting to go to unrestrained rpms. I believe there is some back pressure from the governor arm when trying to hold it open as suggested by John. So, maybe the tweaking I did to the throttle cable and the high speed screw did some good. I'll keep at it. Thanks for all the help. Dave

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~ETC~

i just had the same problem on my simplicity....yes different enine and carb entirely

but the rod that went from the governor bar to the throttle butterfly lever was in the wrong hole the hole was too large causing slack and the ability for the butterfly valve to be sucked open by the engine about half way.

i scratched my head for hours.

then i began examining carbs and noticed to outer most hole was larger.

i figured out it was causing the slack so i moved it down 1 hole now the mower runs great. revs up and down to idle just fine now

hope that may help to get your engine back in proper working order

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WheelHorse_of_course

Dave,

I would take a scribe and mark the end of the governor shaft (coming out of the block).

Then look to see if there is slippage when you move the governor arm with the engine running.

I wonder if that is slipping and therefore the givernor is working internally but slipping.

The other possibility is that shaft has broken or the weld on that to the tab broke (In that case you should have found a piece of metal in the oil pan however.

Or you could remove the arm and rotate the shaft. It should stop in one direction - that is the point you are supposed to have it in when you "calibrate" the governor as you saw in the manual. If that shaft goes round and round then you will need to open her up again

Best of luck :thumbs:

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420lse

Too bad u don't have a pic of the gov. I had the same problem on a Honda motor and it too ran WOT. I'm pretty sure I screwed it trying to use the gov arm as a throtle.(Won't do that again). I dont know what the Kohler gov looks like but when I took the Honda appart the gov slider was actually under the weights instead of riding on top freely. Also It's my understanding that the cotter pins that hold the weights can wear and cause the gov to not function properly.

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