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Kohler SV600 Engine Surging

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ks64
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2020/02/19 20:34:15 (permalink)
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Kohler SV600 Engine Surging

As winter is winding down, I pulled out the lawn tractor to prepare for some lawn work. The mower struggled to start and failed to continue running. The smell of fuel was over-powering so i ordered a new carburator for the Kohler SV600 engine and replaced the spark plug as well.
Engine starts immediately now but continually surges.
I assumed that it was either a case of fuel starvation or a vacuum leak.
I surmised that if it was a vacuum leak, partially choking the engine would smooth it out, but, in fact, it actually started to choke out.
Interesting fact is that if I'm pulling a loaded trailer, which places a considerable load on the engine, all surging goes away, until the terrain levels out at which point it begins to surge once more.
I'm stumped.
What am I missing here?
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    AVB
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    Re: Kohler SV600 Engine Surging 2020/02/20 07:39:46 (permalink)
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    No engine model and spec number posted.
     
    First I assuming you put on an aftermarket carburetor.
     
    It is one of two things since you installed a new carburetor as just a parts replacer. Either it you have the idle speed set too low or the static governor adjustment is off due difference linkage positioning.
     
    The reason it can be the idle speed is that lawn mower runs off the carburetor's idle circuits except when under an load; otherwords, the throttle plate (vane) is nearly closed. If it closes too much it cuts off the fuel so the governor tries to condensate by opening the throttle plate but it usually is too much as overspeeds the set idle speed and tries to close throttle plate to slow the engine back down. Idle should set using a tachometer and set your engine particular spec number idle rpm. Can be from 1750 to 2150 depending on that spec number.
     
    Miss-adjusted governor can do the same thing due to play in the governor linkage system. This why static governor adjustments are done to remove this play. Now the Courage can also have a governor that the flywheels pivot points are worn to a point that static adjustment would need a .010" feeler gauge inserted between the max throttle plate opening stop when setting the static adjustment. This I have seen and done on a few of these Courage engines that continue to surge even when the idle speed was set correctly and had the standard static governor adjustment done. 
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    ks64
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    Re: Kohler SV600 Engine Surging 2020/02/20 10:30:52 (permalink)
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    Thank you for that direction.
    I think you might have hit on the problem with regards to the governor as I simply reconnected everything without really checking for configuration changes in the linkages. 
    You also mentioned the idle adjustment could be the culprit, but, the surging occurs no matter the throttle position unless it is under a heavy load and not just at idle.
    Could it still be the idle adjustment?
     
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    AVB
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    Re: Kohler SV600 Engine Surging 2020/02/20 11:03:17 (permalink)
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    Simply yes. A non loaded engine throttle plate will be nearly closed as there is no load due to governor action. This because with the throttle plate nearly closed it is operating off the idle circuits of the carburetor. Any automatic adjustments by the governor could close the throttle plate too much cutting the available fuel.
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    ks64
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    Re: Kohler SV600 Engine Surging 2020/03/10 08:21:48 (permalink)
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    Gas is from last fall. Could be an issue.
    I did get a chance to look at the idle over the weekend and discovered a secondary choke adjustment that I could modify and high idle and it would take out the surge, however at low idle it came right back. In essence, I did find a partial solution, but, it will end up being more annoying than anything else and I'm not sure how the engine will perform when mowing an incline. It very well might be running too fat at that point.
    One thing that I'm unsure of is the electrical connector at the bottom of the carb bowl. As it will fit in either position, what would be the symptoms of it being connected incorrectly?
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    AVB
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    Re: Kohler SV600 Engine Surging 2020/03/10 09:13:57 (permalink)
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    ks64
    One thing that I'm unsure of is the electrical connector at the bottom of the carb bowl. As it will fit in either position, what would be the symptoms of it being connected incorrectly?


    Doesn't matter which as the solenoid doesn't care which way the current flows through it.
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