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J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7445
Experience:  Owner of outdoor power equipment business, repairing all makes and models.
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I have a Briggs & Stratton single cylinder 18HP Intek OHV engine

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I have a Briggs & Stratton single cylinder 18HP Intek OHV engine on my lawn mower. It wont start due to too much compression. I have been reading that an adjustment to the exhaust valve may correct this. I need to know how to do this.

The specs are .003" on the intake and .005" on the exhaust.


To prepare the engine to set the valves you need to do this. Pull the spark plug out and remove the valve cover. You will then want to turn the engine clockwise as viewed from the flywheel end until the piston is a TOP DEAD CENTER on the compression stroke. Both rockers arms will be loose. You will then need to take a pencil and stick in the cylinder until it touches the piston and put a mark on it. Pull the pencil out and then put another mark 1/4" higher. Put the pencil back in until it touches the piston and then turn Clockwise until the top XXXXX XXXXXnes up with your reference point. You are now ready to set the clearances.




Customer: replied 6 years ago.
Could you explain more about where to insert the pencil, does it go in the spark plug hole? Where do you look to see the piston? Where do you look to see your marks?

Also, do you think that my problem is related to this adjustment?
It sounds like it. You do not really need to use the pencil, but it helps. You put the pencil in the sparkplug hole. The reference point that you use to make the lines does not matter as long as you use it for when you make the first line and then when you put it back in and turn the flywheel until the second marks lines up to it.
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