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joel_400

governor mods

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Well the girlfriend is out of town for a bit more than a month so I have time to play with engines on the dyno...I'm wondering what guys are doing to the governors to pass tech 3600 rpm at no load but then actually run more rpm loaded going down the track? I'm having a hard time finding this "top secret" info on the net. Which is understandable as nobody likes to share thier secrets. I'm just wanting to do a science project more than anything and have a pile of Kohler k series engines and parts to play with, so if it breaks on the dyno I can take the good pieces and throw another together. Haha Also would like to share what I find and maybe even post some videos if I can figure out how to do it!

Joel

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to bypass the governor a simple way would be (on the bench this is) is to rev it up from the carb and when on the track i bypass the arm that link the throttle to the governor with a stiff paper clip or something like that. i've never used this much and i've never raced but this is the only way i know to temporarily, to do it permanently you would either need to remove the air vane or metal spinning weights inside the engine i don't know kohlers very much but i guess small engines are mostly the same.

 

james

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I'm not looking to bypass the governor, just modify it to build more rpm under load yet still tach at a lower set rpm under no load to pass tech. Technically cheating yet everyone does it!

Joel

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You have to start by understanding how the governor works in the first place.  The K series (and many other small engines) use a gear with fly-weights and a spring.  The faster the gear spins the more force the fly-weights exert, usually through a cam or pin.  Pushing against this is a spring tensioned by the throttle lever.  At low throttle the tension is less, high throttle tensions it more.  The throttle plate of the carb is directly related to the position of the fly-weights, when they are pushed in by the spring the carb throttle opens, as they expand out the throttle closes.  

 

The skinny of all this is this:

 

As the engine is loaded at a set speed, it will begin to slow down.  When it slows the force of the flyweights acting against the governor spring lessens, causing the carb throttle to open.  The system balances out when the speed drop opens the carb throttle enough to hold the load.  

 

The more load against the engine, the further the carb throttle must open.  To open the carb further the fly-weights must exert more force against the spring.  This all means that to fully open the carb throttle, the engine speed must drop by X from the user throttle setpoint.  

 

You MUST keep the same spring force (this determines max RPM) but you can play around with the spring rate (this determines the X rpms mentioned above to open the throttle to full).  A stiller stiffer rate spring will move to full open throttle quicker than a weaker spring rate, but will also cause erratic and possibly unstable behavior.  You wouldn't want a large change, only slight.  I'd try using some fine tie-wire to band together a few coils of the factory spring, essentially stiffening it.  You will have to readjust the RPM limiter link after this a bit, then load it up and your full-load RPMs should be a bit higher.

 

 

Please note this is just the theory of it, I've never desired to actually do this as it'd be poorly suited for my daily worker!

Edited by jrc0528
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