View Full Version : OT Govenor RPM for Tecumsea HH120

07-12-2014, 01:36 PM
Hello all. I posted a simular thread awhile back and got some ideas and have just replaced the valves in the engine. It appears that someone replaced a valve seat and never cut it. Thus the valve never seated correctly. Well anyway its running fine now but I cannot find the RPM to set the govenor at. I know there are some pretty knowledgable people here. The engine number is HH120-120045B 7321 08051 This is a cast iron 12 horse horizontal shaft made in 1967, day 321. Thanks

07-12-2014, 02:13 PM
I have a factory manual for the Tecumseh HH120 and strangely it lists every specification and procedure for this engine except rpm specs!
It goes into great detail about governor adjustment procedure and says that the rpm setting will be located in the specs section but alas it is not there.
However a quick search produces the small 8 page pdf below showing various HP ratings of this engine from 1800-3600 rpm.

http://manuals.casecoltingersoll.com/PartsManuals/Tecumseh%20Engine%20Manual%20691393_watermarked.pd f

07-12-2014, 02:27 PM
That rpm would be determined by what you were using the engine to operate.

What's it hooked up to?

07-12-2014, 02:38 PM
Willy, I must have the same manual. Your link says "at 12 horse its 3600 rpm" thus ill set it at 3600.

07-12-2014, 10:58 PM
I think I may have a magneto problem. It fires right up now. But when I rev it up sometimes it breaks up sometimes not. But it sounds as though it's missing at random. No set pattern. How do I test for that?

07-13-2014, 12:31 AM
Does it have points? If so, check he gap and condition, and the capacitor.

07-13-2014, 02:00 AM
RPM's will depend on the load. Shouldn't matter much unless the load is a generator or has a centrifugal clutch.

More likely to be arcing over something it shouldn't if its failing at high RPM (if it is indeed electrical)
Check the points, capacitors (If it has one), spark plug wire, spark plug ceramic insulator (Clean it, inside and outside of engine)

Could also be lack or excess of gas, Cleaning the carb (Pay special attention to nearly invisible pinhole idle jets (Just after the butterfly valve) and such) is always a good idea for ANY engine.

07-13-2014, 09:53 AM
No points. It's electronic. Carb is good

07-13-2014, 10:42 AM
Check the ignition lead clip on the end of the ignition wire, and of course the general condition on of the wire etc. make sure the grounding screws that hold the mag are not corroded. With electronic mags the best way to diagnose is often to substitute known good.

07-13-2014, 01:29 PM
Lakeside53 all connections are good. Wire is good. Substitution is a good way to diagnose. Yes it is. Unfortunately tecumseh has been out of bizz for many years and this electronic mag is a$300 part now. But I did find a site that told how to adapt a dodge electronic ignition to this engine. So I'm in the process of collecting all the needed part

J. Randall
07-13-2014, 05:38 PM
If you don't find anything else, replace the spark plug, if you haven't already. Sometimes they are bad, even though they look fine.

07-13-2014, 08:25 PM
I did replace that also.

07-14-2014, 08:25 AM
you can also ask this question on smokstak.com

07-14-2014, 10:06 AM
Does the engine run erratically only while under a no-load condition or is it worse while under load? If you have positively verified that the carburetor is jetted correctly and functioning properly try closing the spark plug's gap drastically to about half of where it should normally be set at. This is a somewhat crude procedure but I have used it successfully in the past to isolate a functioning but weak ignition system. The very close plug gap will allow the the engine to perform better if the ignition system is weak as it will mask the ignition system's inability to maintain a strong spark under load. A slightly rich air/fuel mixture will also help mask a weak ignition system.

I see you have already discovered the Chrysler ignition module conversion. Below a few additional links to the conversion if you have already not found the yourself.