Tec OVRM120 Valve Adjustment

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  #1  
Old 11-03-09, 02:12 PM
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Tec OVRM120 Valve Adjustment

The factory specs for this engine are .004" on both intake and exhaust valves, cold and at TDC. But, I seen a few posts on some other sites to run the intake at .004 - .006 and the exh at .006-.008 to prevent a burned valve on this engine.

One problem I am having now is the compression release (MCR) is not working well especially when hot, so I want to a do valve clearance check. The engine will spin freely with the plug out. Are the above non-factory settings recommended and will the comp release still work? Also, I see no mention of a TDC mark on the flywheel in the service manual. If there is no mark, is bringing the piston to the top of the stroke on the comp stroke close enough or is the flywheel ignition magnet visible at the coil to locate TDC?

Lastly, service manual calls for a torque wrench on the valve lock nut, in the real world is the torque that critical on this engine? On most other engines I have not used a torque wrench.
 

Last edited by edge10; 11-03-09 at 02:29 PM.
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  #2  
Old 11-03-09, 06:21 PM
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What makes you say MCR is not working well?

Set the valves to Tecumseh specification of 0.004 inch.

The engine should “spin freely with the plug out”.

There is NO TDC mark. The manual states, “Valve lash (between the rocker arm and valve stem) should be set or checked when the engine is cold. The piston should be at T.D.C. on the compression stroke (both valves closed).”

Place a screwdriver in the spark plug hole to see when piston is at TDC. Flywheel magnets will begin to pass coil at TDC. If you do not have a torque wrench just snug the nuts down.
 
  #3  
Old 11-03-09, 08:17 PM
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Originally Posted by Airman View Post
What makes you say MCR is not working well?
The recoil starter is harder to pull than it used to be and the electric start only works when the engine is cold. What I meant to say was the engine will spin freely with the plug out using the electric starter when engine is up to temp. The was done as a quick first test for the the electric starter to eliminate a heat related problem with it. Sorry for the confusion.
 
  #4  
Old 11-04-09, 05:21 AM
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Incorrect valve clearance will not allow compression release to work and the result is too much compression. If the problem remains after adjusting the valves to 0.004 inch then the problem is with compression release.
 
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