[Kartbuilding] Connecting a General Purpose Engine to a Gearbox unit for a Kart

Stephen Burke sburke at burkesys.com
Sun Jan 28 14:04:10 GMT 2007

2 versions of connecting up a general purpose engine to a gearbox.

The First Setup - I got a Honda 50 gearbox. It had 3 gears which I wanted to 
utilise. I already had a centrifical clutch on the general purpose engine, 
however I badly needed gears. The centrifical clutch on the Honda 50 was oil 
based, and I only had the bones of the Honda50 gearbox with no casings.
Using the dry centrifical clutch I connected up the General Purpose engine 
directly to the Input of the Gearbox as can be seen here:
So the engine and gearbox are facing one another (was pretty wide). It was good 
tho - the engine speeded up - and drove the gearbox direct, and from the 
gearbox to the rear axle - sprockets and chains.
Honda50 Gearbox Input shaft:
Honda50 Gearbox Output Shaft - showing gearlever also:
This setup worked fine for a while. However I had to manually apply and setup 
an oil feed to the gearbox - as there was no resevoir of oil etc. It was a very 
wide setup as the engine and gearbox had to be side by side. Easing off the 
throttle to change the gear (via the dry centrifical clutch) wasn't the best 
and the gearbox took a little abuse - but worked ok.

But.......I wanted a manual clutch, and a clutch pedal. So......

The second setup was to get a Honda90 gearbox which had a Manual Clutch (old 
model). The engine had siezed etc. but the clutch and gearbox was fine. I 
removed the Piston Connection Rod, leaving the crankwheel in place (with the 
counterbalance). I sealed up using a plate and instant gasket - the cylinder 
head opening.
Where the alternator/magneto went - I attached a sprocket to the crankshaft. As 
the magneto/alternator was dry (gearbox was sealedup and filled with the 
correct amount of oil for the wet clutch and gearbox.) and I could easily 
attach the sprocket. I initially mounted the engine, then the gearbox in a 
straight line, giving the setup here:
I found that the first engine was pulling the gearbox a lot and it took up a 
lot of room. I then adjusted the engine-gearbox setup, mounting the gearbox 
ontop of the engine!! as can be seen here:
It wasn't pretty (or light!!) but it did work. It gave me a single powerpack 
which i could mount onto the kart and drive the rear axle. The gearbox had too 
good of ratios and I had to mount a large sprocket on the output shaft of the 
gearbox to link up with the rear axle. It did hold fine. It was very heavy. It 
worked fine. I had my manual clutch (woohoooo) and I had my 4 manual gears.
Clutch lever: http://www.kartbuilding.net/gallery/v/Kart_Clearance_and_Mem 
GearLever (via a lever system): 
This setup cost pennies to get working.

However, I started working for the summer, and I came across a crashed 100cc 
motorbike (rxs100)...so thats what I started at and I ended up with a much much 
simpler and easier setup resulting in:

Anyways thats it. It was a HUGE learning experience working with the gearboxes 
etc. getting them to work. So....it all depends on what tools you have, and the 
money available.

( http://www.kartbuilding.net )

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