[DAVETOM]

Hi all,
Got my engine in bits at the moment and while fitting an 18t crank sprocket, I`ve found it rubs on the casing, where it protrudes for the oil seal.1st of all, is this normal? I haven`t got the clutch back on yet so I can`t put a straight edge across, although the bearing hasn`t moved, the spacer is the same, and the new sprocket is the same width as the old one, so unless it was way out before, I`m guessing I may have to relieve the casing?
Secondly, I`m thinking of drilling through from the drive side into the crankcase,, a la the `Rupert Ratio` book, to provide `weir` lubrication to the drive side and possibly improve breathing. Anyone have any tips or do`s and don`ts?Can I do away with the crank oil seal as surely it will be surpus?

cheers Dave

[WALWORTH]

Hi, Davetom. I fitted a Sammy Miller small sprocket kit to a B40 a couple of years ago. It came with a printed instruction that specified that you HAD to relieve the seal housing, to stop the chain doing it for you. It even went so far as to reccommend the use of a "sharp chisel" to remove the offending metal. I think the supplied sael was slightly narrower to allow you to remove this metal, and still have an effective seal in place, if needed.

[mcman56]

I installed an 18 tooth sprocket and used a 40 x 52 x 5 seal. This is 2 mm thinner than the original so 2mm was removed from the case. Basically it was that little lip that stood out on the 1960 cases. Mine was in pieces so I just set it up on a mill to remove the metal.

[DAVETOM]

Cheers lads, got the answer I was hoping for

[nigelog]

Davetom

i did the weir type conversion on mine leaving the two ports tapped in case I needed to blank off again. I have experienced no problems with this method and have had less hassle with primary wear and clutch slip. Just do it as it says in the book

[DAVETOM]

Yes, I`ve done it now, funnily enough I read your blog too and thought I`d try it as it does make sense

[nigelog]

Hi Davetom

I forgot to add that what was not mentioned by Rupert Ratio but I did (I spent so much time looking at the engine during rebuild the idea grew on me) - when you look down the crankcase mouth there is a ledge on both halves of the crankcase just below the barrel lip. On the timing side it is drilled to feed oil to the timing pinion bush. I drilled the primary side the same giving me a a feed that exits just above the primary gear and chain. I ran the engine yesterday with the primary case off as I wanted to check the clutch before replacing the cover and the spray of oil onto the chain and gear is better than I hoped for. I couldnt see the benefit of just leaving out the primary oil seal and hoping for the best. So my oil seal is in place and feed comes pressurised from the crank downstroke. I may have pictures somewhere - if I find i'll post







bottom pic shows ledge on timing side - repeated for primary side to provide feed shown - no discernable ill effects

This post has been edited by nigelog: 04 March 2010 - 04:48 PM

[B40RT]

nigelog, on Mar 4 2010, 04:33 PM, said:

Hi Davetom

I forgot to add that what was not mentioned by Rupert Ratio but I did (I spent so much time looking at the engine during rebuild the idea grew on me) - when you look down the crankcase mouth there is a ledge on both halves of the crankcase just below the barrel lip. On the timing side it is drilled to feed oil to the timing pinion bush. I drilled the primary side the same giving me a a feed that exits just above the primary gear and chain. I ran the engine yesterday with the primary case off as I wanted to check the clutch before replacing the cover and the spray of oil onto the chain and gear is better than I hoped for. I couldnt see the benefit of just leaving out the primary oil seal and hoping for the best. So my oil seal is in place and feed comes pressurised from the crank downstroke. I may have pictures somewhere - if I find i'll post

Maybe a silly question, but how does the oil return ?
To much oil in the primary case causes the clutch to slip when kicking over IME.

[nigelog]

holes drilled through primary side crankcase act as a weir keeping a level in the primary casing for the chain to pick up - the excess crosses back through the two holes into the lower crankcase and returns to the sump / oil feed pick as per normal - all this system does is reroutes it out to the prmary case and back in again so you are working off the one reservoir of oil. The primary case oil therefore is always topped up and always clean and filtered oil.

This post has been edited by nigelog: 04 March 2010 - 05:03 PM

[B40RT]

Thanks nigelog, that explains it.
Dont think I will make this mod a s I prefer TQF in primary (it usually comes out pretty clean)
Also have damaged that casing in the past, and lost some oil and had water ingress !
Ross

[DAVETOM]

Hi Nigelog,
your mod does make sense, it did cross my mind but unlike you i did not work out a solution!. Engine is together now but will prob try that next time its apart. Cheers, Dave