Water pump pulley and belt questions


New to Karting and first time poster…I recently replaced the water pump belts on my kart (it has a Vortex gp) It had the non-braided single loop style that were on the fringe of failing and I replaced both with the braided style. After running the engine on the stand for a minute I noticed one of the belts came off the pully and was resting in the space between the grooves on the pulley. I know the braided belts are thicker but seems as if the belts rest ON TOP of the pulley grooves instead of sitting in the grooves like the non-braided belts did.

My questions:

  1. I know pulleys vary in size based on axle but do the grooves vary in size?
  2. Would adjusting the tension of the water pump fix this issue regardless if the belt sits on or in the grooves?
  3. Is a pulley even necessary or can the belts loop around just the axle? I saw this set up in a video but not sure if this is standard practice

Thanks for the help!

I always just loop the belts around the axle itself.

I cannot speak for the grooves width, but there are different diameter pulleys for the axle available. It kind of depends on your needs. A larger diameter pulley axle will move water faster (less heat absorbed less heat dissipated) versus a smaller diameter axle pulley spins the pump slower (more time for heat to be absorbed and dissipated up to a point). It really depends on your needs and there are several tuning options regardless.

If the belt keeps riding out of the groove, you can just use the bare axle as your pulley. The use of an inline thermostat can cut flow to help maintain minimum temps and taping up the face of the radiator can help increase temps. Tape is cheap (there are also movable curtains available for most brands that perform the same function).

You may want to check the alignment of the two pulleys to make sure something is not askew.

I want to be extra cautious since I don’t have a way to monitor temps and obviously don’t want to over heat the engine. Thanks for the responses, very helpful. Clearly I have a lot to learn about the cooling system.

Don’t overthink it. I have never had issues with cooling, even in hot desert conditions running it directly off the axle.

Thermostat is a good idea for watercooled stuff.