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I have a mower with a briggs and Stratton 18 hp single cylinder motor on it and I can't get the thing to turn over on the compression stroke. Here's what I've done,,,,,,adjusted the valves several different times. checked the compression release and it's working (intake valve opens fully then again only part way) charged the battery, checked the ground, cleaned both battery terminals and the starter is fine. Once it's warmed up it works great. Sometimes when cold it locks up on the compression stroke. If I turn it by hand then try at times it will go but other times it'll stop again. Any ideas?
 

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Sounds like a timing problem. Also ck the fly wheel key.
 

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I had a 15 HP Briggs that would act the same. One day I pulled the plug and it cranked with a lot of gasoline out the plug hole. The selonoid on the fuel line carb bottom was not sealing and allowed gas to dribble into the combustion chamber. I bought a manual fuel shutoff valve for the fuel line and worked great if my rememberer was on.
 

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"The selonoid on the fuel line carb bottom was not sealing and allowed gas to dribble into the combustion chamber. "

Here again is a big mistake many people make. That solenoid DOES NOT, is not intended to, "seal" off gas from the carb. It only blocks the main metering jet to help prevent after fire when the engine is shut off.

Walt Conner
 

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Sometimes cheap or old batteries can cause this. Also the starter may work fine, but they do get weak over time. Also, valves should be .004 and .006 on an OHV like that. Also check to make sure the Aluminum pushrod is on the intake and steel rod is on exhaust. sometimes these pushrods will bend since they arnt very strong, so make sure they arnt bent and check your flywheel key. Try jumping it on a battery you know is good to double check make sure it isnt something as simple as incorrect cranking amps on a battery. Valves can be tricky, so run the mower for an hour or so and THEN set the valves as soon as you shut it off. Watch the oil dripping on the muffler though. Hope you get it. Mine does it too, just have to wait a second and then itll turn over.
 

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"The selonoid on the fuel line carb bottom was not sealing and allowed gas to dribble into the combustion chamber. "

Here again is a big mistake many people make. That solenoid DOES NOT, is not intended to, "seal" off gas from the carb. It only blocks the main metering jet to help prevent after fire when the engine is shut off.

Walt Conner
Yes your right on that one. The needle seat is for that. Those are more than likely those press ins. I use self tapping bolt and 2 screw drivers to remove the seat, then install the seat with a flat punch and thatll cure the fuel prob.
 
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