Hi Joachim
I am the recipient of this bike....it came like this!
The original waterpump I think is still active. I haven't had a chance to test this, having only fired it up and ridden up and down the drive.
But as far as I can tell, the thermostat opens and the temperature is kept constant. I will go for a longer ride soon...but bike is unregistered and I must hide from the local police.
I'm assuming this pump was added to keep the temp down for racing in Japan, but thats a guess only.
I'll have a look for the serial number tomorrow.
I'm planning to put the Nordwest engine I have into this frame, and possibly install some of the better bits from the 350 engine, ie the kickstart and decompressor mechanism.
Neil