Clutch cover hole - what is it?


Hero member
Cambridge, UK
Hi All,

Chasing down a water leak on my 750 Formula (ex Crispin and CJ, as seen in the Perfect Corner Special I and II here... and here!.)

I know that Crispin had the water pump seal replaced at 3CMoto on the trip - you can see that in the video... However when it gets hot it has been blowing water onto my right leg, so I suspected the header tank. However last time I topped her up, there was also some water on the lower left from near the pump again. So I took off the fairing lowers and checked the whole water system. Found the main leak as suspected in the header tank seam as described by Steve B, jotaman, Piet et al in the 750s boiling over thread. Have effected a temporary repair with a soldering iron... Other than iconic944ss's suggestion of a mini moto bottle bodged up, what other options do I have?

Still unsure about the water pump area leak, I carried on and checked over the rest of the water system and there was evidence of radiator fluid below the water pump. However a closer inspection showed that there was a little fluid apparently leaking from a small hole in the bottom of the clutch cover, pretty well immediately below the water pump. Hopefully you can see it in the attached photos...



There appeared to be a slight fluid weep from it but having cleaned the area up and run the bike for half an hour or so, there was no further evidence of any leak whatsoever.

So, the question is: what is the hole? Could it be possibly a drilling for an internal waterway, or gallery? It slants towards the front of the cover, looking reasonable neat as you can see. It's definitely NOT vertical. Should it be plugged? if so with what?

Any help or advice gratefully received!


If it drips out of that hole, the water pump seals are shot......  Time to tear down the pump, replace seals and also the shaft if neccessary!

The shaft wears alarmingly quick, new seals just get chewed up if you re-fit the old shaft ::).

Ah right, it's obvious once you know - now I just need to keep my eyes on it then... As I said, no sign yet of any further drips from it and I've cleaned up the area round it.

As the seals were replaced only about 1800 km ago, if they have gone that implies the shaft is shot too... OK.

I wonder if Crispin knows if 3CMoto replaced the shaft too?

Any idea on where I could source a replacement header tank?

Many thanks.