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Unread 07-28-2007, 11:02 AM
ericpackman ericpackman is offline
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Join Date: Jul 2007
Posts: 1
Default 55 hp Johnson runnin ruff

I've been working on this 55 hp Johnson. I can get it started but it runs rough. I have to have the fast idle cranked up or I have to keep it revving or it will die if it just idles. I also get a miscellaneous backfire and misty spray of fuel out of the top carb. I've done a compression check, spark test, cleaned both carbs, adjusted idle adjustment screws, tried different plugs, and swapped the coils. I'm not sure where to go from here. Any advice?
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Unread 05-04-2008, 10:31 AM
Kent Vogl Kent Vogl is offline
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Join Date: Apr 2008
Location: Fenwick Island Delaware
Posts: 7
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Sounds like the only component you have not ruled out is the reed valve behind the intake plate. Depending on the year and model you may have to remove the powerhead first but more than likely not. The reed valves are not a common problem on a stock motor, but i had a 120 force motor make me scratch my head for some time with similar symptoms some years ago until i removed the intake plate and found one of the reed s had cracked. You have followed the right procedures with spark test, compression test, and carbs, most people don't start there with the basics and run into mis-diagnosis. If you cannot find a parts diagram to get to the reeds e-mail me and I can send you the parts breakdown from my lap top which has parts and diagnostic programs on it.Before getting in too deep pull the flywheel and check the key, backfire and popping are also possible timing symptoms
Good luck,
Kent
mercrunner@comcast.net

Last edited by Kent Vogl; 05-05-2008 at 04:50 PM. Reason: forgot additional causes
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