Hey folks, been a long while but I thought I'd show how we renewed the water pump seal quite cheaply. My brother's blade started leaking coolant from the water pump bleed hole. We stripped the pump down using my hydraulic press and found that the mechanical seal had a split bellows. Honda will only sell a new pump at over 200 and any used pump is going to be risking the same problem as the rubber seals will be similarly hardened over time so there was nothing to do but change the seal.
Easier said than done as it happens because Honda used a Type 73 SPECIAL seal that's an odd size. The seal face and ceramic rotor are identical to a standard 10 seal but they used an over-sized dish to mount the static part. New seal on the left, old seal dish on the right in the pic.

So we need a way to mount the new seal in the hole. We decided to bond it into the old dish, so first job is to cut off the base of the dish to make a ring. I jammed the thing onto a tip-ex pen to hold it and ground the corner away on my bench grinder to cut the base away from the dish.

leaving us with all these bits to assemble:

Bonded the new static seal into the ring of the old one. No need to be super-fussy as it doesn't spin but the tapered lip does a good job of keeping it central anyway:

But now the seat is 1mm thicker so turn 1mm off the face of the pump to give the right spring pressure:

Press in the shaft:

Sealant on the seal and new ceramic in the impeller:

Finally press in the seal:

Impeller was pressed back on and it's all like new again. Job done for a tenner and a couple of hours work.