Tach drive housing with oil seal

[Bonzo]

1974 850 Mk2.

Went to fit a tacho drive housing with oil seal (067254), so removed the old housing without the seal, pulled out the drive gear and removed the o-ring to replace with a new one (061282), scrapping it in the process. I noticed the new o-ring was bigger than the old one



I checked on the AN site and only then did I realize that my drive gear is scrolled (061089/S) and so the smaller o-ring that I need is 065203 (which is listed for a Mk3 Elec Start) and also that my drive gear is unsuitable for the housing with oil seal.



I think my options are to either modify my original housing to accept the oil seal and order the smaller o-ring or buy a new tach drive gear (065201 - not scrolled), but the route I think I'll go is to order 061089 from RGM (£24.90 +vat). It mentions that the o-ring sits on the shaft though I can't see a recess for one on their image.

COMMANDO TACHO WORM GEAR IN FRONT OF CAMSHAFT

COMMANDO TACHO WORM DRIVE, THIS IS THE EARLY STYLE GEAR WHERE THE 'O' RING (061282) SAT ON THE SHAFT AND WENT INTO A SMALL RECESS. FITS ANY COMMANDO WITH THE TACHO CABLE TAKE OFF FRONT RIGHT OF CYLINDER BARREL. IDEAL FOR USE WITH 067254 TACHO HOUSING. GENUINE ORIGINAL FACTORY PART.ALSO SEE

www.rgmnorton.co.uk

A bit more of a palaver than I thought it would be.

 

[ashman]

Cheaper to go buy a full O ring kit from a auto parts shop, i have a complete metric and imperial O ring kits in my workshop just for replacing any size O rings i need for anything.

 

[Torontonian]

You don't want the earlier scrolled one , you want the later solid shaft one .
Mine has fitted a seal , not an o-ring . Can't recall the number , it presses into place .
Another important consideration is to fit a crankcase reed valve .
Do all 3 and the tach drive will never leak again .
I eventually , with evolution , fitted the Smiths electronic instrument option , that reads off of one coil . The tach drive gets a cover plate , sealed up permanent now .

 

[YING]

You don't want the earlier scrolled one , you want the later solid shaft one .
Mine has fitted a seal , not an o-ring . Can't recall the number , it presses into place .
Another important consideration is to fit a crankcase reed valve .
Do all 3 and the tach drive will never leak again .
I eventually , with evolution , fitted the Smiths electronic instrument option , that reads off of one coil . The tach drive gets a cover plate , sealed up permanent now .

Plus there is no cable!
Mike