[Kartbuilding] Lawn mower engine powered wooden go kart

[Stephen Burke]

Hi Max,

The function of the governor is to regulate the speed of the engine to 
keep it at a regular RPM.

Engines for power genators, water pumps and lawnmowers all require the 
engine to keep a "nice" even speed (RPM).

With a governor, if the RPM of the engine drops, then the throttle (or 
valve on the carburetor) is automatically opened more, to allow in more 
petrol mixture and to try and bring back up the rpm of the engine.
Likewise, if the engine RPM increased too much, the governor would close 
the butterfly valve and bring down the rpm of the engine.

So the governor on an engine is to try and regulate the speed of the 
engine keeping it at constant speed.

However for a kart, you want "direct" control of the throttle (and 
butterfly valve on the carburetor).


The governor is "typically" a set of springs connected to a a lever which 
controls the butterfly valve on the carburetor.
For example see: 
http://kartbuilding.net/gallery/v/Engines_for_Karts/General_Purpose_Engine_G42-50/DSC02357.JPG.html
You will notice a set of springs. You will notice where my thumb is shown 
and how there are 2 holes to accept a throttle cable.
There is a very small vertical wire connected to the left of the lever. 
This wire is what directly opens and closes the butterfly valve in the 
carburetor.
To bypass the governer, this is what should be controlled with your gas 
pedal.

Taking a quick look on youtube, I found the following 3 videos.
1: http://www.youtube.com/watch?v=wF1f_I7PfSs
2: http://www.youtube.com/watch?v=Ry6bVpEcO7c
3: http://www.youtube.com/watch?v=DjYVKRv612g

Some videos show people opening up the engine to disable the internals 
which controls the linkage to the throttle on the carburetor. In my 
opinion, it is easier just to control the throttle directly on the 
carburetor. See the end of Video 1 above.

Another option is to "shorten" the length of the springs connected from 
the governor. This makes the springs stiffer and allows more direct 
control of the throttle valve on the carburetor.

Once the governor is disabled, make sure not to rev the guts out of the 
engine.


Hope this helps.
Best of luck,
-Steve



On Fri, 24 Jun 2011, Maximiliano Ichazo wrote:

> Steve,
>
> In the email beolow, you mentioned you have removed the governor. I've got an
> engine (a Chinese copy of an Honda GX) and I was told to remove the governor. I
> don't know what is the function of the governor. What is the adventage to remove
> it? or what is it for?
>
> As always, your comments are greatly appreciated.
>
> Max
>
>
>
>
> ----- Original Message ----
> From: Stephen Burke
> To: Adam Tomlinson
> Cc: kartbuilding
> Sent: Wed, June 22, 2011 8:08:10 PM
> Subject: Re: [Kartbuilding] Lawn mower engine powered wooden go kart
>
> Hi Adam,
>
> I got 30mph in one of my wooden karts and that was with a 3.5hp lawnmower engine
> with the governor removed. You can go faster with a bigger engine, but you have
> to make sure your build quality is perfect. You would also need to use bearings
> for the rear axle (instead of the pipe bushings I outlined on the plans) if you
> want to go faster.
> Also, the way the front axle is pivoted simply, it is not ideal for high speed.
> You can tighten up the front pivot bolt to help make the steering tighter (so
> bumps on the road don't cause the front wheels to pivot).
>
> I hope this helps. Typically wooden karts are the first step to kartbuilding.
> You'll soon progress onto metal based karts.
>
> Best of luck,
> -steve
>
>
>
> On Wed, 22 Jun 2011, Adam Tomlinson wrote:
>
>> Just wondering what the top speed of the wooden engine powered kart is roughly
>> (on flat ground)? I am looking to build this kart and would like to know before
>> I start.
>>
>> Many Thanks
>> Adam Tomlinson
> _______________________________________________