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Tkart magazine

How To | How to install the gear ratio on direct drive karts

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03 September 2019
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In karts, the transferring of driving torque to the rear wheels generated by the engine takes place through a simple configuration which is composed of the sprocket, the chain and the gearwheel itself. In single-speed karts, which do not include a gearbox, the optimal configuration of the sprocket to gearwheel ratio, depending on the engine and the type of track, plays an essential role in achieving the very best performance out of the engines. Whatever the choice from a practical perspective, the correct assembly of the transmission is just as critical for the kart’s reliability on the track. Let us see how to proceed.


The first component to be mounted is the gearwheel support structure, which must be installed on the axle at the height of the key point. At this point, the gearwheel support should not be fastened to the axle, so you can adjust the position of the gearwheel in relation to the sprocket at a later time. Once the gearwheel support is installed, we can move on to the gearwheel and fasten it to the support.


We can now proceed to the engine, which the sprocket is directly associated with. With the engine mounting plate in the correct position on the chassis, we simply set the engine onto its mounting brackets and we get ready to align the gearwheel to the sprocket.
There are several methods to execute this step. The simplest and most precise one uses a laser pointer which, when affixed to the gearwheel it must point to the center of the sprocket to have a perfect alignment. Once we are sure about the position, we can finally secure the gearwheel support to the axle. Then, the axle is turned to verify that the alignment remains stable and constant. In the event that the laser pointer shows different alignments amongst the various parts of the gearwheel, it will be necessary to replace the individual items or adjustments must be made.
Using the laser pointer, the gearwheel is aligned with the engine’s sprocket:

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