How I finally fixed Triumph pre unit chaincase oil leak
I followed several threads on this topic. I use ATF, and even with minimum oil level, high speed rides always ended up with oil getting on the drive chain and then on the rear wheel. This is partly due to the fact that I run without a chain guard.
I tried a phosphor bronze shouldered bush in the large sliding washer, gasket material etc - all to no avail.
As it's heavily modified anyway (including running a longer duplex primary drive chain and unit clutch for years( hint; the unit sprocket has to have the oil seal diameter ground smaller), I decided that I would use the unit engine approach of the sprocket cover with oil seal, fixing the gearbox position and using a unit primary chain tensioner.
I threaded the tensioner spigot 3/8 UNF and used a thinned down nut inside and a serrated stainless flanged nut on the outside
I made an aluminium alloy block (I have a lathe with a milling head) to hold the rear end, keeping the adjuster inside the chaincase. This is fixed in place with 2 x 2BA countersunk screws
I had to cut away part of the alternator mounting to clear the spigot and tensioner blade.
I positioned the sprocket cover having previously set the tensioner and determining the gearbox final position.
I haven't run it yet, as i'm rebuilding the engine. I expect it to work fine but I'll post an update either way.
I've included some pictures and if anyone would like more details just reply.