SLIMLINE GEAR
BOX SEAL HOLDER FOR BSA THREE SPEED ENGINES
The gearbox oil seal holder on the three speed engines gives vary little trouble apart from leaking the odd drip of oil as the seal becomes hard and wears out the sealing lip. The mechanical parts survive the years well and apart from getting chewed by chains jumping worn gearbox sprockets, last the life of the machine. Should you wish to increase the width of your rear chain or fit a sprocket a few teeth smaller than standard you will discover the standard outer seal holder pressing will interfere with chain. To overcome this problem on a racing engine that I was repairing I came up with the modification pictured below. A new outer seal holder is machined up from solid with a thicker flange to accommodate the three countersunk screws .The centre portion houses a seal of reduced outside diameter than the original allowing the use of smaller sprockets even down to the ones favoured by the trials riders amongst us. Reducing the sprocket down to around twelve teeth will prevent using the tab washer and if omitted the chain will ride on the corners of the hexagon nut. One innovative solution 1 have come across to this problem is to grind the case hardened nut to a roughly circular shape and tighten it up with a set of twelve-inch stilsons! | My solution is to machine the hexagon of the nut with a carbide cutter to give a reduced dimension across the flats to clear the chain. The tab washer can be easily reduced by filing or the nut, provided it is fully degreased can be secured with the correct grade of locking compound without any problems.
RCR VILLIERS
DIVISION JULY 2005
Peter Savage 01827-874015
E-mail p.savage56@btinternet.com