Stripping my Burman gearbox for a rebuild I've found a crack between the main bearing and the selector shaft bush hole. The crack does not go all the way through to the inside. Looking at two other shells they both have cracks as well. Is this a common problem? Is it perhaps something that happens but never gets worse and there are lots of Comets running around like this?
G: Gearbox (Single - Burman) Crack in Burman gearbox
- Thread starter chark_mandler
- Start date
The alloy there is not very thick,
I had the circlip groove break away, I think I came home slow in 3 rd ?.
I had it welded with the old circlip in it, To keep the circlip groove shape,
Then just replaced the circlip, I had raced it for a bit As well as on the road, So had a hard life.
That was many years ago, Still plodding about !.
Good Luck, Bill.
I had the circlip groove break away, I think I came home slow in 3 rd ?.
I had it welded with the old circlip in it, To keep the circlip groove shape,
Then just replaced the circlip, I had raced it for a bit As well as on the road, So had a hard life.
That was many years ago, Still plodding about !.
Good Luck, Bill.
Hi Bill, welded the pillar opposite the kickstart stop on the same casing - several oven sessions to try and get all the oil out of the alloy and it was still horrid to weld. Just to get the Comet on the road I'm taking the view that there are lots riding around with a similar hairline crack so am building as is. I'll soon know if the crack goes through the box as it will start weeping. That will give me time to prep a Norton box I've got or repair one of the other Burman casings.
This goes against the grain as its been a total nut and bolt restoration with no corners cut. The bikes being build to ride so I will have to do something.
This goes against the grain as its been a total nut and bolt restoration with no corners cut. The bikes being build to ride so I will have to do something.
Funny, I must have built a dozen BAP gearboxes and have never seen this crack. Usual place of damage is the kickstart quadrant stop and the two circlip grooves. Perhaps some rough beast pressed in a bearing without warming the case first- they should drop in if you chill them a little. Norton boxes are good things, but I've seen them crack between the inner bearing registers. Incidentally the Spares Co. now sell the correct sleeved rubber bush for the quadrant stop. It's now in stock, PR50-134X. Also important is the correct stud PR50-60X/9, 21/64" diameter on the shank-located above the kickstart, although the Spares Co. ones are too short by 3/16" or so, unless they've rectified this.
That crack is not a rare thing, lots of them on other gearboxes to find, not just Burman. I wonder if this is age related and in combination with many hours of high loads. The rear chain forces can be very harsh on the output bearing so the aluminium of the case will be very tired with high mileage. This can lead to cracks in more places. Tired alu is the reason why aircraft have life limits depending on conditions of use. Aerobatic aircraft may require complete overhaul at 300 or 600 hours air work or scrapping . Cylinder heads on typical US turbo piston engines rarely see more than 1000 hours before cracking at the head to cylinder joint, a big thread as the head is screwed down on the steel cylinder. Same with alu conrods: After a certain time of use better scrap them before wrecking your engine.
Wilfried these days had complete disaster when trying to weld the cracks on his Brough Sturmey Archer gearbox. So now a fresh project is on and mill a new gearbox case from a block of 6082 aluminium.
Vic
Wilfried these days had complete disaster when trying to weld the cracks on his Brough Sturmey Archer gearbox. So now a fresh project is on and mill a new gearbox case from a block of 6082 aluminium.
Vic
Wilfried used to post about his bikes, mostly Brough Superiors on his site www.brufnut.de - but he has not posted for ages. He got well into making a replica SS100 from scratch, was preparing to make flywheels and then - silence for over a decade.
Funny thing is, the Sturmey Archer gearbox is the only original part he was using for the SS100 project.
So how are things with Wilfried? Has he built his SS100?
Funny thing is, the Sturmey Archer gearbox is the only original part he was using for the SS100 project.
So how are things with Wilfried? Has he built his SS100?
Wilfried is busy with several things, some repairs to do on other bikes for having them ready for the road. As far as I know the SS 100 project will take a few more years still as so often components take a lot longer than expected. Recently he finished some sets of rear brake hubs for BS . These days you have to do most of the jobs yourself as companies for that kind of work are no longer found easily - too busy with making a living from commercial orders and not a lot of traditional mechanics left in companies for that kind of machining. CNC plus CAD anywhere but motorcycle work is very unlike CNC approach . So in our long telephone hours we discuss ways for a workaround to this dilemma so we can have all work done at home with available machinery. Good thing is we are in retirement, Wilfried just for less than a year, but even so , you take your time and don´t want to rush everything in an advanced age . After all, this is a hobby , not a job.
Vic
Vic
Hello Mark, You maybe right,
I like the old Burman , Tough old beast,
Just the ratios are a bit far apart, But if the Comet had MORE power it maybe OK,
If you don't take the core plug out , You would never know ?,
I rebuilt an unknown one a few years, And didn't take that out.
Maybe a tight rear chain could do damage ?.
Years ago I had a go on an 1150 cc Vincent racer !!, With a Burman Box !,
The owner looked a little worried
, And asked me to take it steady !.He knew I did a bit of Sprinting years ago
.And the "A" Twin had a slightly different, Burman box !.
Will you be using Penright Semi grease, Most of us like it, Magic stuff,
Makes the box almost "Grease tight" !!.
Good Luck, Bill.
Nice, nice.
Lots of chips in the house.
Seeing Wilfrieds page helped me when I was building my SS100. I started with less than him, just a footrest ! I cheated a bit by using existing engine and gearbox internals, though I did manage to find unused flywheels and rods. I had someone machine my heads and barrels but managed everything else myself. Does anyone know where I might get JAP heads machined for a reasonable price now as my source has retired.