BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: Phil C on 23 April, 2022, 17:39:01

Title: Centre stand (1965 B40F)
Post by: Phil C on 23 April, 2022, 17:39:01
Evening everybody,
As it's so difficult to get my bike onto its centre stand, I'm just wondering if it's the correct one for the bike. Its design can be seen on the attached photo. I'm holding it down slightly from its at rest position in order that you can see it better. It measures 10 ins from the pivot centre to the bottom point of the foot. Does anybody know, please? Thanks in advance.
Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 23 April, 2022, 18:07:37
My B40 is 9" and my C15 is 8", the difference is due to the different sized wheels: 18" vs 17"
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 23 April, 2022, 20:41:49
So would you - anybody - say my centre stand is an inch longer than it should be? Can anyone else give dimensions?

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 24 April, 2022, 07:02:31
If you don't believe the figures I provided then have a look at Vol. 2 of Rupert Ratio which verifies these ::)
Title: Re: Centre stand (1965 B40F)
Post by: DAVE BRADY on 24 April, 2022, 08:46:41
Hi Phil,

It looks like you may have a non-standard centre stand.  The return spring also does not look quite right.  However, you could look at reducing the feet on the one you have to shorten it a bit.
I remember my B40 was not easy to get on the main stand even with the proper one fitted.  Although I never got around to doing this, riders used to replace the rear shock top bolt with a rear footrest that would fold down. This gave a good way to hold the bike to assist in lifting it on the stand.

Dave.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 10:44:48
My B40 is 9" and my C15 is 8", the difference is due to the different sized wheels: 18" vs 17"
Spaceman, Thanks very much for the info and obviously I   absolutely believe the figures you gave me, but didn't know whether the stand on your bike was standard, or difficult to use, or what, so just thought I'd ask for further comments. Sorry for any offence, and thanks again. I had looked at Rupert Ratio (vol 2), and read the relevant bits, hoping to find sizes, but stupidly hadn't noticed that the photo (p. 163) has a tape measure on it! I'll also check mine for the part number which is supposed to be cast on the inside of the legs ('40' for C15, '41' for B40, which I imagine has caused misunderstanding occasionally over the years.) Then I guess I'll shorten the feet, and have a look at the spring - thanks for pointing that out, Dave.
Phil
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 12:06:12
Morning again,

Further to my previous post, I've just been out to the garage and had another look at my centre stand. It is embossed "41-4705". Looking at the parts info on the BSAOC website, my bike should have a 4703. So it looks like I do have the wrong one fitted. I had a bit of a look around the info on thew website to see if I could establish which model the 4705 was meant for, but I couldn't find it.

Interestingly (well, to me anyway!), looking closely at the stand, it looks like it might have had foot extensions welded on at some stage (see photo), unless that's just the way it was made. Looking at photos in RR I think it's probably been extended, but I'm not certain, esp as I'm not sure what model 4705 was meant for and exactly what its feet should look like.

If anyone has any relevant info, eg what model the 41-4705 was meant for, and whether mine has had its feet built up, I'd be very interested. 

Phil
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 24 April, 2022, 13:22:15
The complete centre stand comprises a number of separate parts each with there own part number. These numbers, when welded together, comprise the centre stand 41 4703.

Thses separate part numbers will not appear in the parts books.

The stand 41 4703 consists of;

Offside leg part 41 4705
Nearside leg part 41 4706
These legs are an EN8 steel stamping.

Centre stand tube part 40 4722
Spring bracket part 40 4708 EN4 steel strip
Title: Re: Centre stand (1965 B40F)
Post by: AdrianS on 24 April, 2022, 13:40:33
I dont have much trouble getting my B40 onto the centre stand.
Are you shocks the correct length? That can affect getting the bike onto the stand.
As for the side stand......! That certainly could do with modifying to correct the lean angle!
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 14:02:29
I was wrong about the specified part number for my bike. Looking again at the BSAOC website, part number 4703 is for the 1965 B40. But the 1965 B40F (my model) is apparently allocated centre stand 4710.

Both the legs on mine have 41-4705 embossed on their inside. So, going by the info kindly supplied by Julian, I have two offside legs for 4703 (1965 B40.) So I've got the wrong thing. It's all very odd.

I didn't even know there was a 1965 B40 distinct from a 1965 B40F. Was there?

Confusing, eh?!

Phil

PS Adrian, re side stand, thanks for that - it's at the wrong angle? I'll have to look into that.

Title: Re: Centre stand (1965 B40F)
Post by: Mike Farmer on 24 April, 2022, 14:23:14
 :) :) :) :)

I have this problem, but I reckon its down to my lack of ooomph. So I have a 3"x 2"X6" chamfered block of wood. Run rear wheel onto block, put the stand down and rock the bike off the block. Easy peesy.

Mike 8) 8) 8) 8)
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 24 April, 2022, 14:30:20
Phil

I dont think you stand is made of the wrong parts, could well be that both legs are the same basic part but differing only in machining to give off side and nearside different numbers.

My own experience with a 1961 B40 was that it was not particularly easy to get on the stand, no kick leg to get your foot on for example. So your experience may not be much different from that of some other owners and your bike may just be a typical B40.

I would very cautious of shortening the legs you could end up worse than it is already. Sometimes a stand has had pads welded to the feet to compensate for wear in the feet, the pivots or the mounting lugs on the frame
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 24 April, 2022, 15:09:02
If I put my 1965 B40 on the centre stand, the front wheel is barely lifted off the ground. It's possible the stops on the stand are a little worn and the stand slopes forward slightly more than it should although it looks ok to the eye.

If the front wheel on the B40 in question is lifted 2" off the ground when the bike is put on the centre stand then the stand is probably too long. If the wheel is only lifted 1", the stand is ok in terms of length.


Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 17:49:13
Thanks everyone.

When I put the bike on the stand, both wheels are just touching the ground. The front one can be revolved by hand but it is rubbing on the ground. So that, I guess, means either the stand is NOT too long, or maybe the angle it sits at when in use is wrong? Please see photo. Any thoughts please?

Phil.
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 24 April, 2022, 18:13:37
Old photo, not the best quality, of my B40. Back tyre about 1/2 inch off ground.

I think there will be some wear at the top of your stand or the frame mounting lug causing the angle. Looks like a previous owner has welded a pad to the feet to compensate
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 24 April, 2022, 18:23:21
Another view.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 18:56:54
Yes, thanks Julian, clearly mine is at the wrong angle, so presumably there's wear at the top of the legs and/or the lugs on the frame. Hopefully it will be at the top of the legs, as that will probably be easier to fix than the lugs on the frame. I'll put the bike on its sidestand and look to (carefully, so the bike doesn't fall over!) remove the centre stand to have a good look at it.

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 24 April, 2022, 19:21:26
But actually, there must be a better way than having it on the side stand? Do I need to buy some kind of jack, so that I can see the centre stand's operation with it held up clear of the ground somehow?

Phil.
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 24 April, 2022, 19:53:33
The pic shows the top of a C15 stand with the front of the bike on the left. It is the sloping top edge in front of the hole that presses against the frame to stop the forward motion of the stand. As with this example, this edge gets hammered downwards causing the stand to tilt too far forward lowering the height of the bike. To repair, this edge needs to be built back up by welding on metal until the stand angel is correct again.
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 25 April, 2022, 07:57:00
Going from memory, the B40 frame is fitted with two round topped triangular shaped lugs on which the centre stand pivots. The inside half of the lugs is machined so that, above the top of the centre stand mounting arms, the machined parts of the frame lugs provide shallow V-shaped cut-outs. It is these cut-out shapes that limits the travel of the centre stand in both directions.

However, over time, both the V-shaped cut-outs and the triangular top of the centre stand legs will wear from the stand snapping open and closed and therefore the amount of travel will gradually increase. Even with a bare frame, I think it would be very difficult to repair the frame lugs. A replacement centre stand might cure the problem but this will depend on how much the frame lugs are worn. The alternative, as suggested, is to change the shape of the front part of the triangular tops on the centre stand by welding on some metal - a relatively easy job for a welder!

Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 08:59:05
Thanks very much, spaceman. I'll have a look at mine today - then it will probably be clearer to me how exactly it operates and what I can do to repair it. I'll report back.

Meanwhile, any thoughts on the jack/ lift issue?

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 25 April, 2022, 11:32:47
The pictures below show how the centre stand works - this is a C15 frame but will be identical to the B40.

The frame is basically flat between each pair of triangular brackets on the frame and it is this flat surface that limits the travel of the centre stand due to the ~ triangular shape at the top of each leg.

However, examining my example C15 frame, it looks as though most of the wear is probably in the centre stand pivot holes rather than in the bearing surfaces. Having dug this frame out, I will try to work out what angle the centre stand should deploy at and will then repair the centre stand to achieve it. First step, will be to re-bush the centre stand pivot holes to take out the free play and, if necessary, I will then re-profile the top of each leg with a bit of welding.

For the B40 in question, I would recommend taking off the centre stand to see what shape it is in and to see what needs to be done to restore it to the correct deployed geometry.
Title: Re: Centre stand (1965 B40F)
Post by: Pete C on 25 April, 2022, 12:44:32
+1 for Julian.
The stand should be almost vertical in use. Yours has a fair bit of wear on the mounting lugs, stops, etc and it does look like the feet have been added to to compensate so meaning you have to lift higher to get the bike on to the stand.
You neeed to remove the stand and find out where the wear is and after fixing that you can grind off the excess on the feet.

I had the same problem with my B31.
Title: Re: Centre stand (1965 B40F)
Post by: Pete C on 25 April, 2022, 12:46:25
sorry, I had only read the 1st page of comments before posting so didn't see that the topic had been answered  ::) ::)
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 13:23:03
Thanks so far everyone. I'm taking the stand off the bike, which is pretty straightforward except one of the pins won't come out. Used wd40, drift punch, hammer, hot air gun, etc, but so far no joy. I'll get it out eventually and can then have a good look, think, and - crucially!  - discussion on this forum.
  Phil
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 15:24:44
The centre stand is now off the bike. Going by what I can see, and from advice received on this forum, it appears what's needed now is:
1. Build up (with weld) the surface that acts as a stop. By how much I don't know, as I have the bike on its side stand rather than raised up, which would be ideal so that I could them offer the stand up at the correct angle and judge how much weld would be needed. I might need to use guesswork and trial and error. Any thoughts please? (I've no welding gear so might have to take it to my local friendly blacksmith.)

2.  Correct the elongated pivot holes. Basically they need bushing, so I'll have to ask the blacksmith to bore out the holes with a slot drill on a milling machine, turn up some bushes to fit, braze them in place, and finish the holes to size. Need to think about the position of the hole centres.

3. Cut off the extensions a previous owner appears to have welded onto the bottoms of the legs.

Any thoughts on any of the above would be appreciated. Thanks very much.

Phil



Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 25 April, 2022, 16:38:10
I would recommend getting the pivot holes sorted first because you can't work out what re-profiling of the top surface needs to be done with that much free play in the pivot. I've had a close look at the C15 centre stand I've got and decided that the upper most part of the pivot hole is ok and the hole has been elongated downwards - if you take that into account, you can then see where the centre of the hole should be.

Once the pivot holes have been sorted and the extra feet removed from the centre stand, it can be re-fitted after which it should be relatively easy to work out what angle it needs to sit at and to also work out what thickness of metal needs to be added at the top of stand.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 17:27:34
When you say the uppermost part of the hole is okay, do you mean the bit nearest the vee, or the bit that is uppermost when the stand is folded up?  Phil
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 18:05:28
Further to my question in my previous message, it occurs to me that there's not a huge amount of matuerial at the side of the hole for bushing (see photo). Either the wall of the bush on one side is going to be very thin, or the wall of the parent material will be very thin, or they'll both be pretty thin. And of course they will be brazed/welded there. Anyone bushed these things before? Phil
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 25 April, 2022, 19:08:46
The alternative course of action is to use the bike with just the prop stand whilst  searching for a replacement centre stand - you might, in time,  find one which was in acceptable condition.
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 25 April, 2022, 19:48:07
When you say the uppermost part of the hole is okay, do you mean the bit nearest the vee, or the bit that is uppermost when the stand is folded up?  Phil
With the stand vertical, I think most of the force on the pivot holes will have been downwards which will be the direction of maximum wear - the bit of the hole near the V-shaped top to each leg will therefore be relatively unworn and should define where the hole started life.

I don't think there will be any problems with the strength of a repair involving brazing in a bush to restore the pivot holes. However, as an exercise, I am going to carry out the repair on my surplus C15 stand by welding although I may have to find a milling bit to restore the hole afterwards?

In terms of finding a replacement centre stand, I suspect that we are seeing typical wear for a 57 year old motorcycle and you may find it hard to find one in better condition?
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 25 April, 2022, 20:57:32
Decisions, decisions...

I guess it could take years to find a good one? (Good excuse for going to lots of jumbles though! But then there aren't many near me in SWDevon) There wouldn't be any NOS ones, would there?

If the hole wear is at the top end (spaceman seems pretty confident it is) then the bush, which would of course have an off-centre hole, would at the top be, say, 2mm wall thickness, and the parent metal (ie the leg) would have, say, 3mm wall thickness. Or vice-versa, or something very roughly like that. Both the bush and the hole it fits in would need a sizeable chamfer to hold braze, as the braze couldn't be proud (it would have to be dressed back flush) or the thing wouldn't fit in between the frame lugs (I think.) So there would be thin walls, with a chamfer taken out as well. Not much material left then, is there?

I'll be extremely interested to see how spaceman gets on with his surplus C15 stand. Very, very kind of you, spaceman.

Thanks again all. Interesting, isn't it? (mental note: must get a life!)              Phil
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 06:31:17
A thought I've had is that I could leave the hole as it is, and just get the stop surface built up with weld.

But Rupert Ratio (vol 2, p 102-3) talks of refurbishing by repairing the holes, and welding on pads under the feet, but I don't think says anything about building up the stop surface.

Another thought I've had is: I believe the stand is made of malleable cast iron? Would welding compromise it's strength by creating brittleness/cracking? Hmmm... it's beginning to feel a little bit like a can of worms.

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 26 April, 2022, 07:46:22
The centre stand is made of steel as far I can see - there's no reason to make it from cast iron!

I think RR is assuming the only wear is to the pivot holes and the bottom of the feet. From what I can see for the C15 stand that I've got, the top surface is badly distorted from years of hammering as the stand snaps open giving the wrong deployed angle. At a guess, I think the front edge of the bearing surface on the top of each stand legs needs about 1/4" of metal added.

In principle, the pivot holes do not need to be repaired. All that matters is the angle the stand makes with the frame when it deployed and therefore re-profiling the bearing surface to give the correct angle should be sufficient.
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 26 April, 2022, 08:46:18
Go back to my earlier post - the legs are EN8 steel stampings. Google will tell you its properties.

Here is the page from the build specifications.

Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 10:05:20
Thanks Julian. I was going by Rupert Ratio. As I understand it, EN8, back in the day, had quite a bit of carbon in it, and there would be a risk of cracking from welding, but that problem might be solved by preheating. Could be wrong of course. Thanks again. 
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 26 April, 2022, 11:54:16
Rather than repairing a C15 centre stand that I have no use for, I thought I would take a closer look at my B40 centre stand which is a bit marginal in terms of supporting the bike. As expected, it shows quite a bit of wear. The pivot holes exhibit the same level of wear as my C15 centre stand - the centre of the holes have moved downwards by, perhaps, 1/4". The forward ramps at the top of each stand leg which determine the deployed angle of the stand have also been hammered out of shape. Finally, each foot has probably been worn away by at least 1/4".

I'm going to repair the pivot holes first. Once done, I will re-profile the forward ramps on each leg to give me a deployed angle of, say, 15 deg to the vertical - at the moment it is probably about 30 deg. Once these two repairs have been done, I'll then see how much the centre stand feet need to be increased in depth to give me a back wheel 1/2" - 1" off the ground.

In terms of EN8, there's going to be no risk of problems during welding - it's just a slightly higher carbon content mild steel!
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 12:24:54
I'll be very interested in how it goes, spaceman. I take it you have equipment such as welding gear, lathe, maybe be even a milling machine or maybe a pillar drill? Do you plan to weld the bush in place, or braze it? I guess you'll be welding it in, otherwise the welding heat to build up the stop surface would probably melt the braze. I was reading online that EN8 used to have more carbon in it (medium carbon steel) than it does now (unless I misunderstood.) Anyway, please let me know how you get on. Hope it goes well. New pins just arrived in the post here.  Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 26 April, 2022, 13:45:02
If I had an oxy-acetylene torch, I would do a braze repair which, unfortunately, requires the metal to be heated to about 825 deg C! What I'm minded to do at the moment is to fabricate a piece of metal shaped to completely fill each distorted pivot hole and to tack weld them in place. Having done this I can then more easily drill out the hole before completing the welding of what's left of the added metal.

Interestingly, having messed around with fitting my B40 centre stand to the C15 frame I've got, I think I've come to the conclusion that the pivot holes have actually been worn upwards rather than downwards rather counter-intuitively! I will certainly need to double check this before I drill the new holes! 
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 15:54:16
The bearing surface on the frame appears to me to be about 15 degrees to the horizontal (sloping down towards the front.) I guess ideally the striking surface on the top of the leg should hit it flush along its striking length, which appears to be roughly 5/8". So, on mine anyway, the front edge of the leg's striking surface needs to be built up a lot more than the back. I'm guessing around 1/4" more than the back  (but a bit of geometry/ trig would work it out more accurately!) Photo shows one of the worn legs.  Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 26 April, 2022, 16:38:56
That sounds about right to me! I will be working out the overall geometry for my B40 so that I can relate the angle of the centre stand and its length to the height the back wheel lifts off the ground. One thing I need to check is that my rear shocks are of standard length??
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 18:11:37
I'm afraid I don't know what the standard length for the rear shocks is. Here's a photo of mine.
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 26 April, 2022, 19:57:15
Here's the thing - standard length according to RR is 11.3" but mine is 11.9" which seems to be what is now available on the market. Unfortunately, this means the centre stand now needs to lift the bike an extra 0.3" (to give 0.6" at the rear wheel) compared with when the bike was new. Not a lot but needs to be taken into account, at least for my B40!
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 26 April, 2022, 20:30:48
Hmmm... bit of a devil.

How's the hole repair going?

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 06:47:34
I should have it done this morning. Actually looking easier than I thought because I will be able to use some steel rod as the filler material rather than having to laboriously cut out and shape some sheet material. Once tack welded in, I will use my pillar drill to drill out the new pivot holes which, hopefully, should be straightforward.

What I will then need to do is work out what is the steepest angle I can get away with for the centre stand. A quick measurement shows it is currently at about 27 deg from the vertical and I intend to see whether 15 deg would be ok. However, this difference only amounts to about 0.6" in terms of the change in centre stand pivot height above the ground which probably only amounts to about 0.4" at the back wheel. If this is verified when I put the stand back on the B40, I'm going to have to gain any further height by increasing the thickness of the feet?

As said, part of the problem I have to face is that the 11.9" rear shocks I bought many years ago for my B40 are too long and should have been nearer 11.3". So it may turn out that the best I can do with my centre stand mods, is to end up with the back wheel just clear of the ground rather than the 1/2"-1" I would have hoped for.

Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 07:59:21
Please let me know how you get on. I'll be interested to know how much you build up the striking surface by, and also whether you need build up the rear striking surface. Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 08:11:49
I'll post some before and after pics as I progress. In terms of the rear bearing surface on the centre stand, I don't think there will be an issue because the weight of the bike does not come into the wear equation. However, I'll double check the rear stowed clearance when I test fit back on to my B40.

In the meantime, I've ordered a new pair of rear shocks with a length of 11.4". This not because of the centre stand issue as such but is to solve a problem I have with the clearance between the LH pillion foot rest and the brake rod which is marginal due to the longer than OEM rear shocks.
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 11:53:49
Job done. First pic shows one of the pivot holes before repair and the other shows one of the holes after repair. Using my spare C15 frame as a jig, I adjusted the front bearing surface on each leg to give what I judged to be a deployed angle for the stand of about 15 deg from the vertical - previously, it was about 25 deg or so.

When test fitted back on my B40, the difference was very pronounced although the back wheel is probably just touching the ground. However, I've decided that restoring 1/4" extra thickness on the bottom of each foot which is what has worn off over time, which would produce only about 2/3 of this at the back wheel, was not really worth the effort.

Since I've now ordered the correct length of rear shock, this should leave me with the back wheel off the ground by about 1/2" which is probably adequate. In conclusion, I think it was mainly the worn pivot holes that caused my problem with very little repair needed to the bearing surfaces on teh top of each leg.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 12:43:48
Good job, spaceman. I'm not sure I quite follow how the enlarged hole would result in the stand being at the wrong angle. I thought the key issue would have been the striking surface. But anyway, you've obviously sorted it. Thanks for sharing the info and photos.  I plan to get the striking surface at the top of the legs built up by about, say, 1/4" at the front, tapering to virtually nothing at the rear (a length of about 5/8".) But first I'll check that amount by working out the angles, so that I get a pretty  flush strike. I'll probably leave the elongated holes for now and see how I get on.  If you think I'm going down the wrong track, please let me know. Thanks again.      Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 13:58:48
As said, I came to the conclusion that most of the centre stand wear was in the pivot holes - in repairing the holes, I restored the stand deployment angle to what it probably had when it was new. I'm sure you can sort your problem by re-profiling the bearing surfaces on the top of each leg but it will not be easy because the geometry will be a bit intermediate as the pivot point varies when the stand deploys.

I found it quite hard to sort the mechanism even with repaired holes and a C15 clamped upside down in my workshop on which I could test the repairs and make fine adjustments. Without this C15 test jig, I would have struggled to sort the problem. So my advice would be to repair the holes first and then see whether the deployment angle then needs to be changed.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 14:28:42
Getting the holes round again would seem to make sense (as long as the filler material is not too soft and quick to wear.) But I'd be stabbing in the dark a bit as to where the hole centres should be. My inclination would be to follow your suggestion that the correct hole position is at the bottom end of the elongated one. I might just go ahead like that. It's a bit "suck it and see" but there we are. Thanks for help thus far, spaceman.  PS good name, btw. :)
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 15:51:05
Taking a step back, and thinking again about where this discussion started, I think we might have lost sight of the original problem. My issue was how difficult it is to put the bike on its centre stand. That's what started this. The repairs we've been discussing will affect the angle of the stand when it is in use, and are probably worth doing. The stand being at the proper angle might make getting it off the stand easier. But I can't see that they will have any effect on the ease/difficulty with which the bike is put on the stand. It's getting the bike over the stand's vertical point that is hard work. That issue, it seems to me, is determined by the length of the stand's legs in relation to the distance between the stand's pivot point and the ground. I think I have the correct stand, the correct wheels, and the right rear shocks. So whilst making the repairs we've been discussing will hopefully correct the in-use angle of the stand, I'm not sure they will cure the original problem of getting the bike onto the stand, which I'm still none the wiser about. Any thoughts, anyone? Maybe I need to do things like using a block of wood under the back wheel, fitting a lifting handle, etc.   Phil
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 27 April, 2022, 17:08:11
My opinion is that the B40 is not that easy to put on the centre stand, it is a poor design.

I think your analysis is about right. Your stand has been mucked about, the legs on your stand have been extended and that means even more effort to put it on the stand and it probably feels like it flops when it goes over the top and back down a bit so to speak. Also probably a bit harder to push it off the stand because it has to go up to get back to the top before it can go down.

Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 17:38:54
The difficulty of getting a B40 (or any other motor bike) on to its centre stand will relate to the angle the centre stand makes as it is lowered to the ground prior to pulling the bike on to it. The bigger the angle to the vertical, the more force that will need to be used to pull back on the bike. Also, the bigger the angle, the higher the bike will have to be raised before the centre stand tilts forward to lock into the open position.

At the moment, the angle mine hits the ground just before pulling back on the bike is probably about 15 degrees meaning it is easy to get the bike on to centre stand. However, when I fit the slightly shorter replacement shocks, this angle will increase to about 25 degrees and obviously it will then require more force to pull back on the bike.

In the case of the B40 in question, it would be interesting to know what the angle is as the centre standing is lowered to the ground. Rather than trying to measure it directly, it can be determined from the height of centre stand pivot, H, above the ground with the bike vertical and the centre stand stowed, and the length of the centre stand is L - the angle will just be acos( H / L).

If this angle is 30 degs or less then there's probably not going to be much you can do about it but, if for example it is 45 degs or more, there should be room for improvement.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 18:03:14
Spaceman, where did you position your new holes? At the bottom of the old elongated ones?   Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 27 April, 2022, 19:35:17
Yes at the lower position - it's a bit counter-intuitive but, if you consider what happens when the centre stand deploys, you can see that the grinding action of the pivot pin is upwards.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 27 April, 2022, 19:50:41
I keep thinking of potential problems! When you've bushed the holes, and you come to drill the new ones, you need to get them in line with each other. How did you do that?   Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 28 April, 2022, 06:45:54
I basically assumed the lower part of the elongated holes were accurately drilled by BSA and drilled my holes in the same place. On one side, that worked out ok but, on the other side, I had to adjust its position slightly. In hindsight, the approach I took was a little bit crude from an engineering point of view and I was lucky to get away with it.

If I had to do the repair again, I would try to use a milling machine setup to mill out the holes so that I could position them accurately relative to the bearing surface on the top of each centre stand leg. If you don't, the bearing surfaces will not engage properly with the corresponding flat surfaces between the pairs of frame pivot lugs and the stand angles will be completely wrong.

Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 28 April, 2022, 07:19:12
I think that to do this job properly would need either equipment I don't have, and/or money I don't want to spend paying someone else to do it. So I think for now I'll just put the stand back on the bike and live with it, and keep an eye out for a good replacement, as Julian suggested.

So you could say I've achieved nothing and wasted everyone's time. I hope you don't feel the latter. But I've gained an understanding of how the thing works, and it's foibles, and it's been interesting.

When I've reassembled the centre stand, I'll turn to the side stand which, Adrian said recently, needs attention. I'm not sure yet what's wrong with it, or how to remedy it, but I'm guessing maybe the bike is leaning over too far. I'll send some photos, and ask some dumb questions, when I come to looking at it.

Thanks again everyone for your advice.

Phil
Title: Re: Centre stand (1965 B40F)
Post by: Spaceman on 28 April, 2022, 08:43:59
I wasn't happy with the way I repaired my centre stand, for various reasons, and am going to try a different technique with the spare C15 stand I have. Basically, I'm going to try to fill the unwanted part of the elongated hole with weld material rather than welding in a piece of filler metal - success will depend on whether my limited welding skills are up to the job! If the new approach proves to be practical, I would be happy to have a go at repairing your centre stand if you are prepared to take the risk?

In terms of the sidestand, the one on my B40 is pretty useless because it is at the wrong angle and, like yours, it leans the bike over too far. I'll have a close look at it later to see whether I can determine what is causing the problem. Unfortunately, short of heating up the mounting lug to 825 C to melt the braze material to allow the lug to be rotated on the frame, I suspect it will not be an easy problem to sort out.
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 28 April, 2022, 17:04:29
An interesting new old stock stand on ebay, I wonder what it is;

https://www.ebay.co.uk/itm/265666644197?hash=item3ddaf748e5:g:BTgAAOSwkCJiam7C
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 28 April, 2022, 17:13:59
I might ask the seller for some dimensions. But the extension on the leg is something mine doesn't have. Expensive, isn't it?!?      Phil
Title: Re: Centre stand (1965 B40F)
Post by: JulianS on 28 April, 2022, 17:47:24
Dimensions on the last photo of the listing.

Regret stands are expensive, more if they are BSA factory originals and not pattern parts.
Title: Re: Centre stand (1965 B40F)
Post by: AdrianS on 28 April, 2022, 21:32:46
Phil
Sent you a pm.
If you didn’t get it pm me.
Title: Re: Centre stand (1965 B40F)
Post by: hoogerbooger on 08 May, 2022, 11:23:13
Interesting thread.

Seem to have the right stand on mine, but as Rupert Ratio says is typical, worn to the extent neither wheel is off the ground.

With my dickie back has been a lotterie with a bad prize, even with it being shorter. Unfortunately no side stand on mine.
Title: Re: Centre stand (1965 B40F)
Post by: Phil C on 08 May, 2022, 13:25:22
I've decided to live with mine, at least for now.  Might repair or replace it in time, and/or might extend the side stand at some stage. But for now, I'll put up with it.  Phil
Title: Re: Centre stand (1965 B40F)
Post by: chaz on 08 May, 2022, 14:39:07
Ive just fitted an aftermarket sidestand to mine as cant get a decent used one. also with oversize bolt hole its extra play. this one clamps onto the rear footrest arm.it did move as the clamp wasnt able to do up tight enough and the grub screw didnt hold. This was sorted with a plate made up to fit into the original pivot hole and the bracket stops movement. a bit heath robinson but keeps the bike in the position I want.