over revving Briggs 14.5hp IC 280H07

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  #1  
Old 04-22-13, 07:53 PM
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over revving Briggs 14.5hp IC 280H07

Hello,

Replaced control plate containing throttle cable and governor spring (has a linear gear thingy on the back of it). Got her all hooked up but engine severely over revved on start so shut 'er down and did some internet searching.

Adjusted governor, checked choke and throttle linkage. Problem is better but engine still runs at very high rpm on lowest throttle setting. No messing with carb or anything else was done. Looked inside carb though to be sure the valve inside swings with the lever and it does. Can slow down engine only by blocking air intake with my hand, even though the throttle valve is closed as much as possible (top of throttle control swung all the way closed to the idle adjustment screw). Can't figure out how the engine can over rev with no carb changes and throttle plate closed. Out of ideas so any of yours are appreciated. Thanks, Dan.
 
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Old 04-22-13, 08:29 PM
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Did you back out the idle screw some to be sure the throttle plate is completely closed?
 
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Old 04-23-13, 04:37 AM
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Idle adjustment screw was backed out to bare minimum. Could try bending the tab that bumps against the adjustment screw. Should I take off and inspect the carb? Hate to open another can of worms.
Thanks,
Dan
 
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Old 04-23-13, 09:55 AM
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No, don't bend it. The screw should back out far enough that the tab hits the carb casting instead of the screw, or closes fully. I don't see how just changing the throttle control plate only can cause this. If the throttle is closed, it pretty much can't race unless it's getting gas and air from another source. Are you manually pushing the throttle shaft closed with it running?
 
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Old 04-23-13, 07:20 PM
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Throttle tab is hitting the casting, not the idle screw. Like you said, seems that too much air is making it's way past the throttle valve, especially since covering the air intake with my hand allows the engine to idle normally. If I increase the throttle with my hand partially over the carb, the engine tries hard to accelerate. Tightened the screws a little where carb housing screws into the intake with no change. Running out of ideas.
 
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Old 04-23-13, 09:11 PM
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Is the throttle valve inside the carb actually closing tightly? Can you see it seal off completely on the inside of the carb throat? It sounds like the valve is not there, or the screws came loose and let the valve stay open part way. There aren't many possibilities here. The engine has to be getting fuel and air through the carb, and if the throttle plate is closing fully, that can't happen. The only other thing I can think of is if the engine crankcase is full of gas because of a leaking carb and it's getting air from another source.
 
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Old 04-25-13, 06:03 PM
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Fixed it finally

You were right Cheese, not a lot of possibilities. Took off the carb and could easily see the valve was not closing all of the way. Had to bend the tab but on close inspectiion, it looked like it was bent backwards. Maybe when I disconnected the throttle linkage, I pushed on it hard enough to bend the tab out of alignment to begin with. Anyway, thanks to pointing me in the right direction.
 
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Old 04-25-13, 10:39 PM
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No problem, glad I could help.
 
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