# Tecumseh HM100 governor problem?



## wml52 (Feb 17, 2014)

I have a 17 year old 5000-watt Generac generator that is powered by a Tecumseh HM100 10 HP engine that I’ve use as emergency backup for my home. It’s been a great little genny over the years but recently developed a problem that I need your help with.

Normally when I start the engine and let it warm up and stabilize it runs at a no load speed of around 3750 RPM. Yesterday I started the generator up to exercise it and noticed that when I applied a load from a 1600-watt hair dryer it loaded the engine to the point where the RPMs dropped to around 3450 RMP and the speed never increased. When I removed the load the engine returns to the normal 3750-RPM, I never noticed this before. 

I suspect that it may be the governor but I’m not 100% sure. I know the basic function of the governor is to increase or decrease engine RPM depending on load but it does not seem to be doing that. The engine RPM never increased when the load was applied, Is there anything way I can check the operation of the governor or anything I can adjust before pulling the engine apart to check the internal workings of the governor?

Any suggestions or thoughts would be appreciated. Thanks to all.


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## Basementgeek (Feb 7, 2005)

Hi and welcome to TSF

Never want to touch a governor on a generator unless it absolutely necessary.
The engine speed determines the AC cycles, in the USA is 60. In order to set the correct engine speed you need an AC cycle meter.

What are you using to check the RPM's ? 3750 sounds way too fast for a small engine. I would think 3600 is max.

BG


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## wml52 (Feb 17, 2014)

I have a frequency meter to measure Hz, DVM to measure voltage and digital tachometer to measure and set the RPM's. It is not uncommon for a generator like this to have the RPM set-point of 3600 - 3750 RPM, however 3600 RPM would be considered nominal.

The point I was trying to make was the engine RPM's drop significantly when the load is applied. My thinking is, if the governor is set and working properly and the RPM is set at 3600 at no load, the governor should increase the engine RPM's when a load is applied in order to maintain said 3600 RPM. It however is not doing this, as the load increases then engine RPM's decrease dropping the output voltage well below acceptable levels. In addition the load I am applying is much lower then the rated 5000 watt output of the generator.


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## wml52 (Feb 17, 2014)

Problem solved! Turned out to be the hole in the throttle lever where the governor linkage goes had worn the hole bigger and was causing a lot a play in the linkage. The fix was to move the linkage to another hole in the throttle lever and readjusted the governor accordingly. It now runs at 3650 RPM at no load and 3600 RPM at full load with almost no fluctuation in the RPM's. 17 years old and I still can't kill it, I wonder if I'll get another 17 years out of it...lol


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## Basementgeek (Feb 7, 2005)

If the cycles are right, I guess the speed is right.

Lets hope you don't have engine problems seeing how Tecumseh went out of business some years back.

BG


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## wml52 (Feb 17, 2014)

Just an FYI, Tecumseh is still in the small engine business under the name Tecumseh Power and you can still get parts for many of the older engines, however I don't believe they are manufactured in the US any longer, I believe they are manufactured in China, Gee What A Surprise! I doubt the newer engines coming off the assembly line are as long lived as they once were.


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