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Subject: 24hp B&S engine surges at idle

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NTP    Posted 06-14-2018 at 04:00:41 [URL] [DELETE]        [Reply] [Email]  
  • 24hp B&S engine surges at idle
  • I have a zero turn mower that surges when NOT under load. It started doing this when the mower had about 20 hours on it. Now has 90 hours on it.As soon as I engage the blades, it runs like a champ. Dealer said this problem is not covered under warranty, and he sold me some overpriced B&S additive which did nothing. I assume it is a carb problem, but why does it run great when under load and surges when the blades are disengaged? There is no problem running it this way, but sure is agravating. Any ideas?

    steveVa    Posted 06-14-2018 at 06:32:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 24hp B&S engine surges at idle
  • I would guess that the surge is caused by dirt and leaves sticking to the air vane governor and linkage. Most all of those motors have a governor that is blown by the fly wheel to throttle down the idle. When the idle gets low the flywheel does not blow as hard and a spring attached to the throttle overcomes the vane that restricts the throttle and gives more throttle. When it revs up the flywheel blows the vane that again over powers the spring and throttles it back.
    You need to take off the shroud and clean the throttle linkages and spring and vane and pivot points for vane. You don't want to oil those parts because dirt will just stick to the oil and gum them up.

    steveVa    Posted 06-14-2018 at 08:37:09 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 24hp B&S engine surges at idle
  • also, sometimes just upping the idle a little will keep it from surging. Or what some people call searching...
    I have a garden tiller that has done that for 25 years at idle...
    Every time I clean it it works fine till the next year...
    It still works fine when running normal speed all the time.

    NTP    Posted 06-22-2018 at 22:43:40 [URL] [DELETE]        [Reply] [Email]  
  • Re: 24hp B&S engine surges at idle
  • Steve, thanks for the suggestions. What you stated sounds logical. It ran great for the first 20 hours and then started "hunting". Sometimes (not too often) it idles normal when I cut off the PTO.

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