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Discussion Starter · #1 ·
I have a 10.5 Briggs on a Swisher trail mower that will not start. It was last used 3-4 weeks ago, with no problems. Usually choke and pull once, turn choke off and pull once and it will fire. Not last night. I have good spark, good fuel flow to the carb, but do not seem to be getting fuel to the cylinder. Plug does not get wet. Pulled the carb and checked for blockages, appears OK.

I'm thinking I might have an intake valve stuck open. Engine seems to have good compression, but I did not have a guage to check it. Any ideas?

Thanks.
 

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"I'm thinking I might have an intake valve stuck open. Engine seems to have good compression,"

Don't think you would find good compression or any if Intake Valve was stuck open. Since this is a pull start engine I am guessing it would not have a solenoid in the bottom of the carb? Have you tried removing the air cleaner and dribbling some gas from a squirt can or plastic bottle directly into the carb throat to see if it will fire? IF not, I would check the flywheel key given you have good spark and fuel. Very unusual for a key to shear on a belt driven mower but maybe it was not properly torqued to start with.

Walt Conner
 

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Discussion Starter · #3 ·
No solenoid on the bottom of the carb. I tried a little gas in the carb, as well as a little in the cylinder. With the choke on, it would backfire a little through the carb, but with the choke off, it did not do this.

I may be wrong,but if the flywheel key was sheared wouldn't it have died when the key sheared? It was running fine last time I used it, no problems before turning it off.
 

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I too have a swisher trail mower that had the exact same problem. Started easy and ran great until one day it just would not start. After trying everything I could think of, I checked compression and mine had none! The valve seat on the intake valve had popped out and was holding the valve open.
To check this, remove the spark plug, place your thumb over the hole and slowly pull the start rope. It should have plenty of compression to blow past your thumb. Just be sure you don't get bitten by the spark plug wire when doing this.
 

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"I checked compression and mine had none! The valve seat on the intake valve had popped out and was holding the valve open.
To check this, remove the spark plug, place your thumb over the hole and slowly pull the start rope. "

"Engine seems to have good compression, " (from original post)

Walt Conner
 

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Yeah Walt, I read that part too. But the original post also says
I'm thinking I might have an intake valve stuck open.
The one on my Swisher would also seem to have resistance when pulling the start rope but not enough pressure to blow past my thumb when I put it over the plug hole.
So the question is does it have compression or not?
The seat on the intake valve on mine would lift enough to kill the compression when starting but if it ever hit, it would run. After a couple more hours of use, it finally got to where when I would shut it down, the seat would fall out and hold the valve completely open.
 

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Discussion Starter · #7 ·
Slowpete, you were correct. Valve seat came loose and was keeping the valve from closing. Also correct was the fact I was assuming compression due to resistance when pulling the starter rope, since I did not have a tester, and no one at the time to assist me by pulling the rope while I checked at the plug.

Thanks again for the help.
 

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When I repaired mine, I found this article about peening the seat to hold it in place.

PER Notebook

After peening mine, I just had to lap the valve to get the right clearance and it was good to go.
 
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