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Popping


JeffN

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The 8HP Briggs I have in my 728 pops at fast idle and stumbles at slow idle. It seems to run fine at part throttle. If you put the throttle at slow idle it will stumble and then die. At fast idle it misses, pops and when it pops there is a slight puff and a spark or flame that comes out of the muffler. Is it a carb adjustment problem? It has a new spark plug and it turns over and starts flawlessly. Any suggestions? Thanks.
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Willing to bet it's the flywheel key that's bad. If it's partially sheared, it throws the timing off and causes all sorts of grief. The key is only about $0.50.[A href='http://www.wheatfarm.com']http://www.wheatfarm.com[/a]
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Jeff, Just for "by-chance". Try something simple first. Unscrew the idle and the high speed needle valves out of carb. Turn the engine over a few times. Re-install the needle valves "finger-tight" then, back them both out approx 1 1/2 turns. It should start and run pretty good then. If it is not popping, fine tune the idle valve while idling. Fine tune the high speed valve at high speed with the mower deck running. This makes the engine work a little and you'll know if it's starving for gas. If this doesn't work, refer to the other suggestions above. Suggested just in case it could be a little dirt or out of adjustment. Good luck! PUT DECK ALL THE WAY DOWN AND WATCH YOUR TOES!!!!!!!! One other possibility - It could have carbon build-up in the cylinder head or under either valve. (usually the exhaust) You might pull off the head and clean off any carbon build-up and make sure valves are not sticking.. Marion W. Kerr
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Well I took off the head and cleaned up the carbon build up and I also checked the flywheel to see if the key was sheared. The flywheel looked like it was aligned up with the key just fine. I couldn't take the flywheel off since I don't have a puller yet so I couldn't check the points. I started it up and it seemed to run better but it still has a slight stumble/pop when moving the throttle from slow to fast. Could this just be a carb adjustment? I also noticed that it does puff a bit when throttling up. Does this mean it needs a ring job? Thanks.
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