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Valve Adjustment

Tex 40's Avatar
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01-12-03, 08:00 PM   #1  
Tex 40
Tecumseh Valve Adjustment

I have a Miller Welder/Generator with the Tecumseh OHM 120. I think it is a 1991 model. I got it used so i am not sure how many hours it has been used. How often do the valves need to be checked and what is the procedure for doing this? Also, the stock muffler looks looks like it has alot of back pressure. Since this just sets there and runs at about 3600 rpm wouldn't it be more efficient and maybe run cooler with a straight pipe of about 12-14 inches in length? It is already loud when running so i don't think the noise would be changed that much. Thanks for your information.

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cheese's Avatar
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01-12-03, 11:11 PM   #2  
Hello Tex 40!

The valve clearances seldom get checked until problems occurr, lol. It wouldn't hurt to check them at around 100 hrs I guess. To check them, remove the valve cover and position the engine at top dead center. Then use a feeler gague of the specified thickness to set the clearance between the valve and the rocker arm.

You can improve efficiency and power a good bit just by letting the engine breathe easier...as you mentioned. I would, however, suggest installing a "Y" at the exhaust and fitting the engine with 2 mufflers. This will quiet it down as well as let if flow much better.

Hope this helps!

"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

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01-13-03, 10:21 PM   #3  


Tecumseh made very few of that model number. Yours should
have push rod tubes and the 2-screw valve cover...correct?
As Cheese suggested....at TDC, compression stroke, where
BOTH valves are closed/seated....set intake @ .002, and
exhaust @ .004. Tecumseh offers an O-ring kit for that to
seal any oil leaks that might be occuring due to brittle, old
O-rings (part #35332). They also offer a rocker arm kit with
ALL the O-rings (except the ones for the push rod tubes),
part #730221A. The rocker arm kit contains new rockers,
rocker arm studs, lock nuts, pal nuts, and O-rings. If you go
with the rocker arm kit, order (4) push rod tubes O-rings,
part # 33481. If the engine has a LOT of time on it....the
rocker arm kit and O-rings would be a good idea. A repair
manual for that engine is part #740043. This covers OHV
engines and repair/service tips on them.


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01-13-03, 10:41 PM   #4  
Tex 40
Hey guys thanks for the information on the valve adjustment. Yes it does have the push rod tubes and the 2 screw valve cover. A repair manual is a good idea especially since i am not that familiar with small engines.

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