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JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1140
Experience:  Owner/Service Technician at S & J Small Engines
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I have a Duro Star 7.0 HP OHV engine and it won't fire or

Customer Question

I have a Duro Star 7.0 HP OHV engine and it won't fire or start even with a small shot of ether. It has good spark at plug tip. Seemed like no compression so I remove valve cover and the exh valve is not moving. The bridge is so loose I can lift it off without backing off the adjusting not with massive gap. I need to know what the valve gap tolerances are for this engine.
JA: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?
Customer: Yes
JA: Do you plan on doing the work yourself?
Customer: Yes. I am an ASE certified Master Truck technician so very familiar with all pre cranking steps.Fuel good, clean and treated for modern gasoline and stabilized. Air intake free and clear. Good bright spark at the spark plug tip and jumping gap properly. I just need the valve gap specification so I can get compression to suck in the fuel/air mix.
JA: Anything else we should know to help you best?
Customer: No, just need the valve gap tolerances in either thousandths or millmeters.
Submitted: 1 month ago.
Category: Small Engine
Expert:  JohnF2015 replied 1 month ago.

Hi, my name is***** will be assisting you.

The valve clearance on this will be .004 inches on all valves with engine cold.

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Customer: replied 1 month ago.
Correct me if I'm wrong, that is top dead center, both valve closed?
Expert:  JohnF2015 replied 1 month ago.

The way that I normally suggest doing it is to rotate the engine until one valve is fully open and set the opposite valve then rotate the engine until the other valve is fully open that you just set and set the opposite valve. Because of mechanical compression release mechanisms built into the engine anymore this is the best way to approach setting the valve clearances otherwise there is a lot of guesswork if trying to set them at TDC.