Tutorial On Kohler Generator Governor Setting

[HeavyHaulTrucker]

From: HeavyHaulTrucker
Sent: 7/16/2004 

I started a new discussion since it seems that the topic of HOW to set the governor on the Kohler 4CM21 genset has never come up, and I have come across something that I thought was unique -- but actually turns out to be quite common, according to the Kohler factory!

Does your Kohler genset seem to strain under load?  Does the governor push the throttle up against the idle stop screw when under load, but increase RPM when you remove the load?  Is your voltage chronically low (95 to 105 volts) when the A/C is on?

The problem, especially if the genset was rebuilt by an authorized Kohler service center, could very well be that the governor shaft/ gear is set backwards!  The symptoms listed above are about 95% indicative of this problem, according to Kohler -- it seems that, since the governor internal workings are not discussed in the service manual (it was designed to be "set & forget" at the factory), no one but them knows how to actually align the governor shaft/ gear if the collar is removed.

So here is how you do it:
Remove the governor arm, and swing it out of the way.  You should also remove the steel fuel line from the shut-off solenoid to the carb for easier access.
Unscrew the "collar" around the governor shaft and take it off.  Remove the bushing from the shaft and set it aside.
Grasp the shaft with your thumb and index finger, and pull it toward you; it will come partway out, but the "gear" will not allow it to come all the way out.  You will notice it feels loose in the hole.
Gently rotate the shaft about 5 degrees either way.  If you can feel the "gear" catching to the right side of the shaft, then you have this problem.  You need to rotate the shaft so that the "gear" catches on the left side of the shaft, and locks in when pushed; you will feel it "snap" into position, and you should be able to turn the shaft only about 5 degrees from stop to stop.  Re-install the shaft bushing and the collar, then re-set the governor arm per the instructions in the Kohler manual (a pair of small vise-grips is really handy for holding the shaft in position when adjusting & tightening the governor arm locking nut).  Re-install the spring.
Set up your AC voltmeter where you can see it, and back out the idle stop screw a few turns.  Start your genset up and allow it to come up to speed.
You will notice that the governor arm will remain all the way to the left for a few seconds, then it will swing into action.  Watch your voltmeter, and set the idle stop screw so that you have 120 to 125 volts at "no-load".
Have a helper turn on your roof AC, first on just the "Fan" position.  You will notice that the governor arm will advance a bit to the left, and the engine exhaust note will deepen a bit.  Now have your helper turn the AC control to "Cool" -- you will notice the governor arm move a bit further to the left, and the engine exhaust note will noticeably deepen.  But you will also notice that engine RPM will stay virtually constant, and your voltmeter should read between 117 and 120 volts.
Problem fixed!  The Kohler 4CM21 genset is an 1800 RPM generator, and will regulate voltage to plus or minus 1% when set properly.  It seems that, according to Kohler, many owners have had the problem with the brass screws on the throttle butterfly breaking, leading to full-throttle operation at above 1800 RPM.  Many owners have wrongly assumed that the governor needed adjustment and, when standard arm adjustment did not do the trick, then opened up the governor shaft assembly and re-assembled it wrong.  This "sort of" cured the problem, since engine RPM was then set by using the idle stop screw -- but the load sensing capability of the governor was almost completely disabled!

John

[DanD2Soon]

Sent: 7/16/2004

Thanks John,

I printed your message and added it to your great .pdf version of the 4CM21 Manual - haven't tackled mine yet, but have no fear about doing it with all this documentation!

Thanks again,
DanD