8hp Briggs won't start

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  #1  
Old 08-14-10, 01:59 PM
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8hp Briggs won't start

I have a 8hp B&S motor (mod 190707, type 5851-01, code 8610090) on a Murray riding mower from 1987. I cleaned the carb, installed the correct plug Campion CJ19LM (I hope it is the correct one, there was a CJ8 when I got it) and even tried a different coil from another mower but it still won't start. When I turn the key the engine "pops" but will not run. It is almost like the timing is off. Even with a shot of starting fluid into the carb it does the same thing. I think I may have been better at this stuff when I was 13 but I am older and stumped. Any help will be GREATLY appriciated. This mower has been sitting about 1 1/2 years if it helps. THANKS!
 
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Old 08-14-10, 05:03 PM
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grancpe,

While it's not very common on a belt drive machine but the flywheel key can still shear, That would be one guess. Then given the fact the machine has sat for that long, Carbon on the piston/valves can dry out then once spun over again the carbon breaks loose and gets stuck under the valves. A non seating/closing valve can cause popping out the intake or exhaust.

Either fix would be a new flywheel key and or remove the head and decarbon the combustion chamber (head/piston/valves and seats).


Good Luck
 
  #3  
Old 08-15-10, 07:29 AM
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The intake valve is locking in the open position. I took off the head and spun the motor and the valve won't close, unless I whack it. I know that isn't probably smart but It seems I may have to break down the motor anyway. While turning the motor by hand it is VERY stiff while the intake valve is opening. Do you think it is just gummed up or can it be bent. If bent I guess I will have to break down the motor. Let me know if I am on the right track. Thanks.
 
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Old 08-15-10, 11:20 AM
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The valve is not likely bent, Just gummed up from sitting.

Remove the carb and then the valve cover (where the breather hose connects). With the valve closed you can pop the valve retainer loose then remove the valve for cleaning.

The retainer has a elongated hole in the center, When pried back and pushed off center it will release the valve.

Use carb & choke spray cleaner to remove the gum from the valve and guide then coat the valve with oil upon re-installation.....
 
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