Small Engines (Lawn Mowers, etc.): Generator governor, excess vibration, ron snyder

Question
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Followup To
Question -
Hi Eric - Thanks for being available.  I recently bought a used motorhome that has a 5.0 KV generator with an Onan engine.  It runs fine, but once in a while during operation it starts to pulse back and forth rapidly, fast and slow and back again.  I believe it is the governor causing this to happen.  The engine only has 525 hours on it, which is nothing for one of these engines.  This usually occurs when there is very little load on the generator and only lasts ten to fifteen seconds, then it resumes normal operation.  Any helpful ideas on how to stop this crazy carrying on?  Sincerely, Ron Snyder
Answer -
Many gensets actually surge without a load on them, especially as the equipment ages.

Many technicians blame the governor but it is usually (99% of the time)something else causing the governor to surge like a dirty carburetor.  

A few questions.  Has the engine recently been serviced?  Oil, air filter, fuel filter cleaned/replaced?  Are the engine mounting bolts securely tight?  Loose mounting bolts cause excess vibration which affects the governor.

Gensets governor springs can be more sensitive than other applications...has the engine RMP speed recently been checked.

Let me know the answers.
Eric

I don't know if the previous owner had the generator serviced before I bought it, but I doubt it.  I have not done anything to it.  The RPM speed has not been checked.  I don't believe the mounting bolts are loose, but it does set in rubber mounts.  How do you check the RPM.  It has to be set at a certain speed to keep the 60 cps on the generator, right?

Answer
We have had some Generac genset rubber engine mounting brackets that needed replacement  because the engine was surging; I don't recall the model but I know we replaced a lot of mounts.

As for the RMP, you are correct about the speed to maintain 60 Hz.  We have a special tool that checkes the gensets frequency, engine speed and wattage output with and without a load.

You can check the engine speed with single cylinder tach but again this is a fairly specialized tool.

Honestly I would recommend have the genset tested at you local dealer to make sure it is operating correctly.
Let me know if you have any other questions.
Eric