How exactly do lawn mower engines work?


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Old 06-16-14, 07:07 AM
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How exactly do lawn mower engines work?

I am trying to build a beefed up go kart and I have a lawn mower engine that I can use but lawn mower engines are vertical driven and a go kart is usually driven with a horizontal mount. How do I make the conversion, should I just use a gear box? Also how do the governors work, my budy build one with an old 5hp briggs and stratton and he tore the governor off why did he do this? any ideas?...thanx guys.
 
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Old 06-16-14, 07:58 AM
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You are best to find a horizontal shaft engine. You will need a pretty sturdy gearbox and they are pretty hard to find.

Inside the case of the engine is a little centrifugal mechanism. When the engine is not turning a spring moves the governor lever to the full throttle position. The instant the engine begins to turn the governor moves to the idle position. The throttle is connected via a spring and fights the governor. The more throttle you want the throttle lever pull on the spring harder and the faster the engine turns the harder the governor works to close the throttle. The balance between those two opposing forces is what holds a stable rpm.

Removing or disconnecting the governor removes automatic control and limit of the engine's rpms. The engine can be turned faster and generate more power. Of course you never get anything for free so the penalty is extra wear on the engine and the risk of catastrophic failure like a broken connecting rod.
 
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Old 06-20-14, 06:23 AM
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Been an awfully long time since I built go carts but motorcycle engines and gearboxes had the right geometry back then. Lawn mowers are wrong by 90 degrees. Last time I looked at home brewed go carts folk were using chainsaw motors with centrifugal clutches.
 
 

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