@darkman, I'm glad to see another of your riveting (no pun intended) build threads. Looks like this one could be a doozy. But what would your builds be without challenges... and you've definitely shown us that you're up to challenges. Looking forward to following along on this one!
When i rode the bike to see just what might req doing i was unhappy with the long gate between each of the gears, after stripping the box looks like the worn cam plate is the problem.
Worn! blimey maybe this bike was in the 1950 TT and then run up a drag strip without using the clutch just to see what would happen. I've never seen a cam plate come apart like that. Always something new.....oh well, it'd only be boring otherwise.
Heck, I've been into that stage of life for about 50 years, darkman ....... Duralumin - or, colloquially, "dural" - is SUPPOSED to be a stronger product than raw or machined aluminium ("a-loom-inum" if you're a septic! ) and, as I recall, was considered the dog's dangly bits in the sixties for fabricating things like engine mounting plates for Trumpet engines into proper frames.
Cylinder head decoked, seats cut and valves lapped in and rebuilt, a coat of high temp back and rocker boxes cleaned with 3M wheel ready for polishing.
this machine would originally have had a bush rather than a seal? im not familiar with how these were put together. ive seen several small cotter pins used to hold seals in before in 650 conversions- just inserted at three spots through a drillway. cutting a groove for a snalring is much better, but much more difficult.
Yes early bikes has a bush and one of the previous owners had attempted a seal conversion at some point leaving the bush in place and removing just enough metal to fit a seal held in with sealer and two wire hoops, bit of a mess so had Pat remove it all and rebuild with weld and do the job properly
The primary case took some grinding to remove the corrosion from battery acid spillage in its past, a bit more smoothing out with finer grade of wet n dry and will be ready for polishing, managed to finish off the gearbox and timing cover though.
Welding day today, had my mate Steve TIG weld the crankcase and gearbox case that had cracked and then fit a side stand lug as it was an optional extra back in 1950.
Good job/s. Hopefully that crankcase weld went well for the bearing.....a great skill to have that TIG welding.
Bearing inner recess has to machined and an insert fitted as old bearing had spun in the case and made it oversize :-(
Update on the worn cam plate, its a casting made from ZAMAK (or Zamac, formerly trademarked as MAZAK) is a family of alloys with a base metal of zinc and alloying elements of aluminium, magnesium, and copper.
Primary side crank case weld cleaned up on the inside and new outer bearing along with and insert to take up the slack as old bearing had spun in the case.
That's bloody good work getting that race square to the casing so the crank runs nice. Some engineering firms are worth their weight.
