Burman 4th Gear Selector Meltdown

Matty

Well Known and Active Forum User
VOC Member
Hi
You will find that I referred to Peter Barker as a supplier for this bearing in a reply on 17 September and agree that the price from other nameless suppliers is very high, probably because they have to have the bearings made or specially processed by firms with large overheads
I use one I bought from him some years ago, with both the seals left in and it has been fine.
My reasoning is that the bearings in car alternators are usually sealed both sides and normally are no problem for 100,000 miles plus
 

brian gains

Well Known and Active Forum User
VOC Member
Hi Peter , yes I'd be happy to take up your offer. I can't mail you as it seems this function isn't available to non members . Workout what the postage would be to West Sussex and let me know, 2nd class is OK as I am waiting on other parts.
Text me ( 07733 401008 ) bank details for transfer or your preferred way of taking payment. Much appreciated.
 

brian gains

Well Known and Active Forum User
VOC Member
Peter , Sorry , I've been trying for several hours but can't open up 'conversation'.
"Oops! We ran into some problems. Please try again later. More error details may be in the browser console".
I'll try again tomorrow AM. Regardless, many thanks for the offer.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Hi Peter , yes I'd be happy to take up your offer. I can't mail you as it seems this function isn't available to non members . Workout what the postage would be to West Sussex and let me know, 2nd class is OK as I am waiting on other parts.
Text me ( 07733 401008 ) bank details for transfer or your preferred way of taking payment. Much appreciated.
Easy Fix - become a member, not a squatter
 

brian gains

Well Known and Active Forum User
VOC Member
Thanks for your comment's MartinG .
Just a little background; For me one of the best assets of the VOC are the forums and information that can be gleaned from them and having been a member I have also met some very knowledgeable people.
I also think it is more than reasonable that people who are not paid up members have restricted access to areas of the VOC site. Yes, I see my situation may be seen as 'having your cake and eating it'.
However my situation presently is that access to public areas of the site is erratic and sometimes totally unavailable, I don't have this issue with other forums where I am a member. Thinking this was possibly because I was a non member I contacted Graham Smith earlier this year and enquired if by being a paid up member would mean having ready swift access, his response was that the issues I experience are not due to any limitations imposed by the Webmaster. Therefore for some reason my erratic available access is limited by some parameter at my end , which again is odd as I don't have the same issues elsewhere on the internet.
So in consideration of this would you pay for a service that you did not have ready guaranteed access to?
Please don't take any umbrage at this post as that is not what is intended, more so just to state that I am aware of how things may appear.
 

Matty

Well Known and Active Forum User
VOC Member
Hi Brian. Welcome to the Club
I have not had any real problems with the site even though I am usually only getting about 1 Meg of broadband here in the sticks.
Matty
 

brian gains

Well Known and Active Forum User
VOC Member
A final update, I hope, and I shall forego descriptions of stripped threads, gear selector lay shaft pawls incorrectly located, seating outer cover only to notice the kick start ratchet gear and main shaft nut had been forgotten and other such buffoonery.

So at my last posting I thought I had identified the reason for 4th gear not selecting was that the retaining circlip on the drive side had become unseated due to the outer retaining ‘land’ failing and allowing the gearbox main shaft bearing to walk out and consequently the final drive 4th gear following on so the dogs would not engage.

I had the circlip outer ‘land’ tigged up and the circlip groove re machined.
thumbnail_20191005_132134_resized.jpg
thumbnail_20191012_124430_resized.jpg
Although the main shaft bearing didn’t run roughly there did seem a lot of play between inner and outer race and as I can’t think that the bearing location would require C3 clearance in this application which is what the play seemed to equate with I used the opportunity to replace it. This was done by taking advantage of the generous offer by A_HRD of a shielded bearing.

So all machining done the bearing freshly out of the freezer was dropped into the heated case and.....it would not rotate as it became apparent that the gear case wall that acts a stop/seat for the bearing had slightly mushroomed out and fouled the inner race. To make matters worse on closer inspection there were hairline cracks radiating from the centre main shaft porthole in the case; b*gger!.

So head scratch time. I cant see a reason for maintaining the small diameter of the casing bearing seat as the only purpose is to reduce the migration of the semi fluid grease through an open bearing and seeing as the new bearing was shielded all that was required was a sufficient seat for the bearing to sit/ register on. Back to the machinist and welding shop, that are luckily only a few units apart, for modifications to be made.
thumbnail_20191108_125020_resized.jpg


I was slightly concerned that as there were no definite dimensions to work to and that the case had obviously distorted where the bearing seated that the machine work would establish it correctly from the sketchy dimensions taken pre work. On assembly of the bearing and main shaft output gear it was satisfying to see that the face of the output gear was 109.12mm from the face of the gearbox, this was at least in the ballpark of the dimension I had read elsewhere on the forum to look for.

So assembly finally complete bar primary drive cover, by rotating the rear wheel all gears appeared to be engaging. Due to rain all I have done is take it a couple of 100m up the lane and 4th now engages, however I achieved this result for a couple of hundred miles earlier in the summer so fingers X’d. Also appears to be some clutch slip in first gear, I thought initially the noise was the rear wheel spinning in the gravel so am hoping the clatter is just the clutch plate noise exacerbated by there being no cover; think Ducati.

So thanks again to A_HRD, other members for words of support, Malcolm the machinist and to add a bit of provenance to the Comet the welding work was carried out by the outfit that built John Surtees racing chassis.

If I post again on this topic it will be about how to fit a Norton/AMC box.
 

nkt267

Well Known and Active Forum User
VOC Member
A final update, I hope, and I shall forego descriptions of stripped threads, gear selector lay shaft pawls incorrectly located, seating outer cover only to notice the kick start ratchet gear and main shaft nut had been forgotten and other such buffoonery.

So at my last posting I thought I had identified the reason for 4th gear not selecting was that the retaining circlip on the drive side had become unseated due to the outer retaining ‘land’ failing and allowing the gearbox main shaft bearing to walk out and consequently the final drive 4th gear following on so the dogs would not engage.

I had the circlip outer ‘land’ tigged up and the circlip groove re machined.
View attachment 30062
View attachment 30063
Although the main shaft bearing didn’t run roughly there did seem a lot of play between inner and outer race and as I can’t think that the bearing location would require C3 clearance in this application which is what the play seemed to equate with I used the opportunity to replace it. This was done by taking advantage of the generous offer by A_HRD of a shielded bearing.

So all machining done the bearing freshly out of the freezer was dropped into the heated case and.....it would not rotate as it became apparent that the gear case wall that acts a stop/seat for the bearing had slightly mushroomed out and fouled the inner race. To make matters worse on closer inspection there were hairline cracks radiating from the centre main shaft porthole in the case; b*gger!.

So head scratch time. I cant see a reason for maintaining the small diameter of the casing bearing seat as the only purpose is to reduce the migration of the semi fluid grease through an open bearing and seeing as the new bearing was shielded all that was required was a sufficient seat for the bearing to sit/ register on. Back to the machinist and welding shop, that are luckily only a few units apart, for modifications to be made.
View attachment 30064


I was slightly concerned that as there were no definite dimensions to work to and that the case had obviously distorted where the bearing seated that the machine work would establish it correctly from the sketchy dimensions taken pre work. On assembly of the bearing and main shaft output gear it was satisfying to see that the face of the output gear was 109.12mm from the face of the gearbox, this was at least in the ballpark of the dimension I had read elsewhere on the forum to look for.

So assembly finally complete bar primary drive cover, by rotating the rear wheel all gears appeared to be engaging. Due to rain all I have done is take it a couple of 100m up the lane and 4th now engages, however I achieved this result for a couple of hundred miles earlier in the summer so fingers X’d. Also appears to be some clutch slip in first gear, I thought initially the noise was the rear wheel spinning in the gravel so am hoping the clatter is just the clutch plate noise exacerbated by there being no cover; think Ducati.

So thanks again to A_HRD, other members for words of support, Malcolm the machinist and to add a bit of provenance to the Comet the welding work was carried out by the outfit that built John Surtees racing chassis.

If I post again on this topic it will be about how to fit a Norton/AMC box.
I've got the info on that that I can Email----If you ever need it, hopefully you won't..John
 

Matty

Well Known and Active Forum User
VOC Member
I still have my old damaged casing with a modified output bearing area because this had been cracked and welded up in 1957 after a tooth broke off, jammed the box bent the shafts etc.
In order to fit a standard imperial bearing in 1957, when I was a poor apprentice ( who used a small legacy to buy the bike) a sleeve had been made to act as a conversion for the output bearing.
This bodge had worked until about 10 years ago, though it always leaked grease onto the output sprocket and chain a bit.
I found a good casing a few years ago (from clevtrev) and built the parts into it with a dragonfly seal on the output which I had a thin groove machined in to seal the outer and used a sealed bearing.
This has been very successful for around 6,000 miles now though I had used some shims to optimise the 4th Gear engagement to around 4mm.
I have done a few other bodges to my old casing to get round the fact that the inner flange is damaged, and think it would work OK as a spare for a while if desperate.
Matty
 
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