Leakey rev counter drive

[Chris N]

in an attempt to reduce the number of oil spots left on other peoples drives i thought i would have a go at fixing the leak from the joint between the aluminium casting and the steel gear housing.
there seamed to be a lot of play between the two parts.



after a while it dawned on me that the two grub screws were there to be screwd in to start separating the unit from the head,a nice touch.
having removed the unit it became obvious the problem was the retaining nut was loose,i could undo it with a finger.


not having a special tool,butchering an old socket of the correct diameter with a dremel resulted in something that would do the job nicely.



with a slightly thicker o ring fitted and the threads degreased and a couple of drops of locktite,it all went back together.job done,or so i thought.



oddly a couple of hundred miles later oil drops started leaking from the aluminium end cap.It all came off the bike again,i checked the unit was not bottoming out on the slot in the camshaft and i have no idea why it started from there.after cleaning a bead of glue is the best i can do.

a while later oil made its way past the glue so i degreased it and araldited a flattened coin over the end cap which did the job.

for a while ,now it comes out of the other cap but rather than seal that and have it going up the cable i have learned to live with the odd drop and enjoy riding the bike.

[Rob B]

Hi Chris,

One thing to remember when using the camshaft bearing jacking screws is to check that the respective camshaft is "off cam". In other words, the cam lobes are facing away from the buckets. Can be done by removing the plug and checking for TDC on compression, not on valve overlap. Other than that, I always use automotive clear silicone for all jointing faces on the Hesketh engine, just as they did in the factory - not bathroom sealant though, although that actually works too :-)  Proper motorcycle engineers will cringe at this but the cheapo clear silicone snot simply works whereas you can spend a fortune on Rocol Hylomar, STAG Wellseal, Heldite and all manner of other fancy stuff that simply won't work with a Hesketh engine.

There is a lip seal inside the right-angle rev-counter drive unit which always leaks so the best thing is to also use a bit of the clear silicone when tightening up the cable nut. Oil then travels some way up the inside of the cable but never seams to make it up as far as the rev-counter, except after a very long run...

RB