High RPM when PTO engaged and clutch is depressed

[WRN55]

My 9N is experiencing an issue of very high sudden RPM increase when I depress the clutch while brush hogging before digging too far into it I m just asking is this an issue with the governor or could it be the overrun clutch on the PTO?
Thank you in advance.
William Nelson
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[Jim.ME]

How long have you had this tractor and cutter? How much have you run it cutting? Is this issue something new that developed recently, or has it been doing it right along?

An increase in RPM when the load is removed can be normal. If you had to increase the throttle setting while cutting to hold RPMs, when you push the clutch, you release the load, and the governor brings the no load rpms up to where you have increased the hand throttle setting to.

 

[Btzj02]

A failed ORC will push the tractor foreward with the clutch pushed in. The momentum of the spinning mass will drive the rear wheels. I would start trouble shooting the governor, carburetor and linkage if the engine races after a sudden removel of egine load.

 

[Tony in SD]

To me, that would indicate that you are over loading the mower causing the engine to loose RPMs. Then when you press the clutch the engine would be under no load and would regain its normal RPM
for the throttle setting. Just because the mower is a certain width, doesnt mean you have to cut the whole width of the mower, especially it it is tall and/or thick vegetation. I would suggest taking a
pass only a half width of the mower and see what happens.

 

[Caryc]

(quoted from post at 08:17:10 12/03/23) To me, that would indicate that you are over loading the mower causing the engine to loose RPMs. Then when you press the clutch the engine would be under no load and would regain its normal RPM
for the throttle setting. Just because the mower is a certain width, doesnt mean you have to cut the whole width of the mower, especially it it is tall and/or thick vegetation. I would suggest taking a
pass only a half width of the mower and see what happens.

I'll second that answer.

 

[WRN55]

Thank you all for the quick responses. Very much appreciated

I agree and understand the issue of load on the engine. When I said increased RPM, I really should ve included that it s far above the normal speed for that throttle setting, and if I bump the throttle down a notch or two it returns to what I consider normal engine speed. If it does turn out to be a governor issue are their thoughts on brands or manufacturers to avoid or recommend.

 

[WRN55]

Looking at the governor on my 9n it appears to have been replaced at some point and not the original governor, so I wonder if I just have a piece of junk.

 

[Hemmjo]

It you set the throttle to a certain RPM, the governor is supposed to
maintain that RPM or close, within the HP limits of your engine. If the load is increased the throttle opens the carb more to maintain proper clean RPM.

If, when the load is reduced, (pushing in the clutch) something
prevents the linkage from closing the throttle plate the RPMs will
increase.

See if you can make this happen while you are watching the carb
linkage. When the load is reduce the governor should try to close the
throttle plate. If it does try to slow the engine, but the engine remains
at high RPM. The problem is in the linkage. If the governor does not
try to slow the engine, the problem is with the governor.

 

[WRN55]

Thank you for the reply, I appreciate your suggestions. I m anxious to get back out to the property to some troubleshooting

 

[DanielW]

Sounds like a possible governor issue. Those governors often have to
be adjusted/rebuilt.

A few more details might help us diagnose, however: Does this happen
with no implement attached? What about with an implement that draws
less HP? When the RPM jumps up, does it stay up, or does it settle
back down after a few seconds.

I'll bet that governor really has that throttle plate opened up as
wide as it can when bush-hogging. I'm surprised you're able to run a
bush hog with any decency behind a 9N. Bush hogs can really suck the
HP. I have smaller 4' bush hog I've pulled behind my 2N, but even
with its rebuilt engine it's still more load than I'd really want to
regularly have on it. It's ok for trimming grass or pasture, but it's
definitely not a unit I'm going to do any serious brush-clearing
with.

 

[Btzj02]

(quoted from post at 13:48:52 12/03/23)
Looking at the governor on my 9n it appears to have been replaced at some point and not the original governor, so I wonder if I just have a piece of junk.

If you like to tinker: A couple years ago a person on this forum posted that he discovered that the "new" after market governor was assembled incorrectly. He described a similar throttle response like you described. He found that the Fork (governor), part # 18235 was installed backwards. His post described how he removed the part, flipped it over, reinstalled it and all was well. I personally rebuilt the original Governor so I can't claim any experience with this fix of the aftermarket governor but it might be worth a try?!