http://eziautoparts.com.au/pdf/Davies_Craig_Electric_Water_Pumps.pdfI think this would offer us quite a few advantages over the mechanical water pump currently used in our scooters:
1) We could use any coolant we wanted, even coolants containing silicon. Currently we can't use silicon-based coolants (which work really well with aluminum engines, as ours are) due to the problem of mechanical seal wear on the pump. The electric pump is magnetically-driven, so there are no seals to wear out.
2) Low current draw. It only takes about 15 watts maximum.
3) Decent flow. About 4 gal / min at maximum pump speed.
{ASIDE: Does anyone know what the maximum flow rate is on the mechanical pump?}
4) Avoiding heat soak. After you shut down your hot engine, the coolant system can no longer do its job of removing excess heat. With an electric pump, the controller can be set to run for up to 2 minutes after shutdown to prevent heat soak.
5) More usable power at the rear wheel. Because the mechanical water pump has to work from idle RPM up to 8000 RPM, it's designed to provide sufficient water flow at idle, and more than sufficient at higher RPMs. So at max RPM, it's pushing more water than it needs to, which just gets recirculated in the engine if the thermostat isn't open fully. With the electric pump and controller, pump speed is set to what is needed to maintain temperatures, and nothing more. By removing the inefficient mechanical pump (with it's excess pumping power loss at high RPMs and the power loss of friction in the mechanical seals), and substituting an electric pump that takes at most about 15 watts, we have more usable power at the rear wheel.
6) Small size. 3.33" x 3.81" total. Hopefully, it'll fit right under that front cover below the front of the seat. If not, the metal tube coming from the radiator can be cut a bit, and it can be mounted on the inside of the kickstand support. The mechanical pump, pump housing and drive shaft would be taken out, and replaced by a similarly-shaped metal blank with a gasket to seal it.
7) The controller can be set up to give an indication (via LEDs mounted in the speedometer housing) of the pump speed (the brighter the LED, the faster the pump is running; or get a combination Red-Green-Blue LED, and set it up so that the LED shows blue at low temps, green at 'just right' temps, and red at maximum temp (and therefore maximum pump speed) triggered off the voltage the pump is running at), and whether the cooling fan is running (if the cooling fan LED is on, the fan is running).
I think I'll be ordering this and trying to fit it to the Yager when my wife and kids go back to Taiwan in March. A few advantages of doing it then:
1) I'll have more free time.
2) I can get dirty working on the bike without her nagging.
3) No kids picking up parts and making them disappear.
4) I can make a mess in the garage and she won't nag.
5) I'll have exclusive use of the car so the scooter can be torn down and worked on.