The chain’s tension does not affect the performance of the single-speed kart engine

If the chain is too tight, it heats up more easily. Consequently, this increases both its wear and that of the sprocket, until it reaches a breaking point. In this way, the reliability is compromised, and the performance is affected as the engine is not “free” to unload its power to the wheel.
The chain must have the right tension while on the track as this can affect the chassis and axle flexibility, modifying the distance between the gearwheel and the sprocket. These factors should be always kept into consideration in the mounting phase of the engine to the chassis.

That is very true! This is the only way to mount the main bearings in the engine. In addition to cooling the bearings, it is necessary to heat the crankcase. The reason is simple: bearings and crankcases are manufactured with extremely strict tolerance levels. We, in the assembly line, use large furnaces which heat crankcases to 80 °C, while we cool the bearings with nitrogen. In this way, exploiting the metals properties of expanding (with extreme heat) and shrinking (with intense cooling) depending on the temperature, we are able to easily insert the bearings, even using hands and without unnecessary exertion. The enthusiasts, who do not have furnaces and nitrogen, have to make due utilizing the freezer (the refrigerator is not sufficient as it does not generate a proper cooling temperature) and a hair dryer. There are no other great alternatives if one wants to implement these processes. One needs to make do with what one has available…