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Tkart magazine

How To | Changing the rubber belts on a water pump

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17 August 2016
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They represent a key element of engine reliability and, in particular, the cooling system. Rubber belts connect the water pump to the rotation of the axle, which in turn is driven by the engine through a rack and pinion transmission. The pump circulates water in the radiator: the greater the rotation speed of the axle and, therefore, of the kart, the faster the water flows. Obviously, it needs to be a good quality water pump, not one that cavitates (i.e. creates air bubbles in water inside the pump, which affect the circulation of the cooling liquid). The pump was inside on the “old” KF engine. Nowadays, OK engines have gone back to fitting externally mounted pumps (as was the case on 100 cc engines), which therefore require rubber bands and also means simpler engines, as well as facilitating work on the water pumps themselves.


If the rubber bands break, cooling stops and engine temperature rises, leading to a loss of performance and, in the long run, the risk of seizure. If you have a telemetry that shows the water temperature on the steering wheel screen, perhaps with an alarm at maximum temperature, you can receive a warning before irreparable damage is caused. If this is not the case, i.e. no water temperature sensor, more experienced drivers typically notice a loss of power and, in some cases, engine knocking noise.


It may seem absurd, but such a simple element causes all sorts of problems when it needs replacing. In fact, the location of the pump behind the driver’s seat and the position of the rubber bands on the axle require the rubber bands to be inserted so that the kart’s rear axle fits inside them. However, rubber bands are circular in shape and closed and the only way to fit new ones is to loosen the screws on the axle, the disc housing, gearwheel support and hubs, remove the axle itself, hoping it comes out easily, and insert the new pair of rubber bands before reassembling the axle. It is a long and arduous task. It becomes very long if the axle jams in the bearing seats or the gearwheel and disc housing jam on it.

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