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Valve adjustment help


Ojiisan's Avatar
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Join Date: Oct 2008
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11-01-08, 04:00 PM   #1  
Valve adjustment help

The instructions for OHV adjustment for a 14.5 Briggs & Stratton engine mention going to TDC on the compression stroke, continue until the piston moves doen 1/4" and adjust the valves. Intake at about .004 and exhaust about .006. Is it necessary to begin on the compression stroke? If so why and how can I identify the compression stroke. Thanks

 
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30yearTech's Avatar
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11-01-08, 04:44 PM   #2  
Yes, it's important that the valves are adjusted on the compression stroke. The reason is this is the only time both valves are completely closed.

Remove the spark plug. Rotating the flywheel clockwise (looking down from the top on a vertical shaft or from the front on a horizontal shaft engine) observe the rocker arm and valve operation, when the intake valve closes this is the start of the compression stroke. Insert a probe into the spark plug hole (straw, pencil, screw driver etc...) as the piston move up in the cylinder, the probe will be pushed out the spark plug hole. When the probe stops coming out this is Top Dead Center, continue past while applying a little downward pressure on the probe. When the probe retreats into the spark plug hole a 1/4" stop, this is the position for setting the valve clearances.

 
Ojiisan's Avatar
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11-05-08, 09:06 AM   #3  
Thank you and I now have the valves adjusted as you said. I have fresh oil, the carburator (Walbro)has been rebuilt in a shop, the engine starts easily in full choke, it continues to run until it is moved off the choke position into full throttle. At this time it surges, pops, and the governor arm is in a back and forth motion. The govenor arm is free of binding and in a static position the throttle is wide open. I am lost again so help is appreciated.

 
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11-05-08, 03:09 PM   #4  
it's starving for fuel. check the main jet, fuel filter, fuel line and any high speed adjustment for lean setting.

 
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11-05-08, 03:47 PM   #5  
Try spraying carb cleaner along the mating surfaces behind the carb and intake manifold while the engine is surging to see it the engine tempo changes if so you have found the leak causing your lean condition. Have a good one. Geo

 
30yearTech's Avatar
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11-05-08, 04:18 PM   #6  
Try geo's trick, if you find nothing, then I think the shop that worked on your carburetor missed something and may need to check it over again.

 
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