On my clone 39cc polini engine made my own water pump mounting brackets from Stanley gate hinges and flat bar from the hardware store. Like CAM2 said many ways to mount a pump. Trouble is you have to idle the engine fast enough to make the clutch grab and turn the pump. I looked for a small electric water pump, you run off a small battery, w/ on & off, so it pumps at idle.
See photo.
Polini has the better solution over the Blata engine when it comes to cooling especially in their element which is racing....If you can ever imagine an engine becoming too cooled down you'd just picture a Blata….Polini had the better idea letting the inertia of the bike control cooling as the longest a racebike sits idle is maybe 30 seconds to a minute running on the starting line...
You push a polini back to the pits you can benefit from the waterpump turning and helping the engine cooldown faster unlike the Blata too...
You need some sort of heat build-up to help ignite the mix....If the engine runs too cool it will never operate in its peak efficiency rate and Blata thrives on that slow heat-up cylinder effect....
On one of the Blata engines I tried foregoing the exhaust port flange cooling mod plus let the water literally flow free as it could to get the efficiency threshold higher which resulted in quite a few engine failures....It was only when I lessened the diameter of the output hose to get the water to flow at a slower rate to absorb more heat is when the engines started to gain longevity but lost that insane punch so I just tuned it on methanol and went super lean on the tune....LOL
