B&s 42a707 18.5hp

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Old 04-15-11, 05:48 AM
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B&s 42a707 18.5hp

I have recently obtained a little used Dynamark 42" rider with a B&S 18.5HP motor. (42A707 1653 01) It had been sitting in storage for about 5 years unused. I took it home, dusted it off, changed the oil, drained the gasoline(tank, line and filter), and charged the battery. This thing looks brand new. Started it up. It started pretty quickly; about the 4th try. Spitted and sputtered a little which I expected. The only problem is now it starts and runs fine but it idles erratically; fast, slow, fast, slow, fast, slow. This is a wide range of full throttle to low throttle. Sprayed a little "Blaster" carb cleaner in while running. No change. When I look down in the carb, I see the throttle valve opening and closing, thus the idle speed flucuations. I'm a handy guy and don't have any problem on working on this, but I never have and would like some guidance on what I should be looking for/doing. Thanks for any advice you may offer!
 
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Old 04-15-11, 10:02 AM
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See if you can get it to smooth out using partial choke, sounds like carb needs some cleaning or attention.
 
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Old 04-15-11, 10:10 AM
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Yes, the idle does "level" with a slight choke, though it runs rough at that point. I plan to break it down this weekend, blast out all the ports and hope to get it back together. I've done weed-eaters and chain saws but never had the pleasure on a rider. Any advice?
 
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Old 04-15-11, 10:12 AM
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Prolly just a good cleaning will do it, just make sure all gaskets are in good shape or replaced.
 
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Old 04-15-11, 09:53 PM
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Just a tip: Don't take the fuel pump at the front of the carb apart. Leave it alone since it appears to be working. Just take the top of the carb off and blow out all the passages and clean the bowl, and remove the bowl plug on the side of the carb and clean the main jet behind the plug. Taking the fuel pump apart will likely result in having to rebuild it.
 
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Old 04-18-11, 09:40 AM
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Excellent! Didn't get to work on it yet, but I have confidence that I will get it running now. Thanks!
 
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