Under my Primary lurks...

[Stuart]

I had the primary cover off the 850cc Ruggerfield today and thought I'd post a few pictures. I like the tensioner May have to seperate the engine 29T cog from that block out front of it if I'm to put something slightly bigger on. Will I get away with 31T I ask myself or just got for 30T? Clutch has 56T.

[oldbmw]

After carefully studying the power curve diagrams from Hitchcocks.. it is clear that (Enfield, so presumably all bikes) transmission losses are much more a factor of transmission speed than transmitted power. IE the faster the transmission runs teh more power it absorbs irrespective of teh power being transmitted. So if at all possible try to acheive the gearing by having a smaller rear sprocket.

When you change sprockets and therfore chain lengths be careful not to create a resonant pattern... I will give an example of a very bad setup

Engine sprocket 20 teeth
clutch sprocket 40 teeth
chain 80 links.

this will concentrate all the wear on two sets of 3-4 clutch hub teeth and 4 sets of 3/4 chain links

as the engine sprocket is bolted to the crankshaft, no matter what size of sprocket you have it will always be synchronised with the power pulse and wear he same 3/4 teeth. periodically move it around if possible.

a much better arrangement would be
engine sprocket 21 teeth
clutch sprocket 43 teeth
chain length 83 links

That way the wear will be evenly spread over all the clutch hub teeth and all the chain links. An undocumented property of older Triumphs is they always used prime numbers wherever practicable to spread out wear on transmissions and idler timing pinions. ( got to have exactly 2:1 for teh timing ratio )

[andrewaust]

Remember sprockets that are an uneven number wear better , that's also a good point oldbmw, multi cylinder engines depending on there firing positions, will also change things too.

Great little setup on the tensioner/inner chaincase Stuart, looks like the fellow was a real tinkerer who owned the bike , Gee the RPM's should be down with the primary gearing on the high side?

[oldbmw]

Remember sprockets that are an uneven number wear better , that's also a good point oldbmw, multi cylinder engines depending on there firing positions, will also change things too.

Not so much uneven numbers, but Prime number. Sorry I forgot about multies, I tend to think either of singles or paralell twins... But the general principle still holds good... Note a triple ( 240 degrees apart has three wear points on the engine sprocket, wheras a four cylinder has only two
paralell twins and singles only one, 270 and 180 degree and usually V twins have Two, just like the fours .

The point I was trying to make was you can easily save a hp or two by lowering the transmisson speeds and make the gearing up on the rear sprocket.