If you have followed the previous thread then you will appreciate the problems I have had with the Burman clutch.
Now my gearbox has expired. I had the engine rebuilt by Maughan's in 2008....no problem hear but the bike terminated in June in the Dolomites with a clutch problem .....awful design IMHO. With a new Conway clutch I thought all would be fine last Sat. With Bob Anderson and Paul Packman in pursuit I was "making good progress" however after 20 or so miles an awful screech at 60mph in top.......clutch in ....drifted to a halt. When I looked down I fully expected to see oil and bits of broken chaincase.
It worked in 1, 2 and 3rd gear but just a jangle of noise and neutrals in top gear... so got home at 50mph or so in 1,2 and 3 gears and the gearbox accumulated 4000 miles since I last disassembled it in 2008 to add BSF threads to the studs per Richardson.
It took me three hours minimum to remove the gear box and primary side and I discovered that the top gear selector had effectively formed braze on the top gear dog on the main shaft..... see attached pictures. (Takes me a day or two to reassemble as I did last week)
Everyone except Pete Deadman declared "lack of lubrication" as the cause at the Aldershot Section on Monday night and I was condemned for draining the oil and adding more grease (to cure the oil leaks). On closer examination it would seem the forked selector has been under pressure on one side trying to force the top gear into the final drive cog and accordingly welded itself and disintegrated.
On a visit (courtesy of Trevor Girton) to Maughan's yesterday, Steve had never seen anything like it. Later on arrival at the new VOCS shop in Kettering Ian Savage, Jenny Bloor and new storeman John Gunn seemed prepared to drop everything to help us.....sorry you never got to drink your cuppa Ian. They were extremely busy trying to get organised and shipping orders etc. Great team and excellent long-term facility.
Nothing was too much trouble for Ian and he empathised that he had experienced exactly the same problem with his Comet ...in his case it turned out to be main shaft bushes creeping in the main output gear. This is the normal first failure point on a Burman. In my case this turns out to be not the cause. So I immediately thought I had dislodged the circlip retaining the ball bearing at the selector end of the main shaft (Conways warn you about this potential problem when fitting their Honda clutch).....This was ok too.
Undoubtedly the selector fork is trying to press the top gear into mesh with the output sprocket main shaft and something is working against it. I cannot figure what is causing the interference. Could it be that the steel bush for the cam assembly is too deep into the casting?
The pin on the selector fork is rather worn as a result of the work it has tried to perform. This fork, incidentally, was replaced by the previous owner so there seems to be an endemic fault in the box. Possibly the the brazing/weld build up has occurred over my last 400o miles on the bike.....and Sat. was the final straw. Still I was lucky the whole machine did not just lock up!
Just a word of warning and sympathy for those who have had no practice in the art of assembling the kickstart and gear selector mechanism......if you think that is tricky (doing all this whilst the gasket cement is setting and the grease is dropping out) then don't get involved in sorting out a gearbox that may be an amalgam of differing parts.
All suggestions welcome
Vic
PS does anyone have an oil tight Burman box?
PPS VOCS do not stock the main shaft gear selector but Ian is on the job.
PPS Aren't Burman drawings and parts lists awful!
