Hi
First BSA to own, quick question, I have the engine on my work bench, should I be able to engage all gears whilst in this position by turning the gear sprocket ?
Thanks,
Yes you should, it was a bit fiddly on my B25, it sometimes needed a good yank on the gear lever
You haven't got much leverage using the engine sprocket - if you can hold the engine steady, it might be easier to run through the gears using the kickstart lever.
Hi
Thanks for your help. The engine was rebuilt couple years ago by previous owner, lots of new parts, still struggling to select any gears except first and neutral. Engine on bench minus clutch etc, looks like I might have to remove inner cover with gears and selector to have look, seems not too bad but don't like removing gearboxes, any tips or pit falls doing the job ?
It's an easy job especially with the clutch removed because all the gearbox innards should come away with the inner timing cover when you remove it.
However, it would be interesting to know what happens when you try to change up from neutral. For example, do you get full travel on the gear lever but nothing happens and it makes no sounds even when you try to rotate the gears with the kickstarter?
Hi
From neutral I can click up a gear, back down to neutral but then cannot seem to be able to engage any other gears below just fresh air., no click or engagement of any gears.
For whatever reason, it sounds as though the gear change quadrant is not able to rotate the camplate as it should - normally, when the camplate is moved by the gear lever via the quadrant, it slots into the next detent position and at the same time moves the pinions via the selector forks to set up the next gear. The problem could be as simple as a broken detent spring. However, it should be obvious what the problem is after you withdraw the innards attached to the inner timing cover.
Hi
Many thanks for your help and advice.
I will remove gear cluster and take a look.
When the cluster is out should I be able to fit the gear lever and try to select the gears at this stage ?
You should be able to exercise all the gears with a bit of manual help with everything on the bench but bear in mind it will all be a bit floppy because the LH end of everything will not be supported; and there will be no detent spring to define each detent position of the camplate. Hopefully, you will see the problem straightaway when you pull out the innards - there's only a small number of things that could possibly be wrong with it.
Hi
Removed the cluster and good / bad news for me.
When removing the cluster a couple of gears, washer and a selector fork fell out , not sure if this is normal.
So, I cannot see why the gears will not engage, all parts seem to be there and I checked with the parts manual that all the gears, washers etc are all present and the correct ones.
I will now try to assemble all correctly and see what happens, the main problem I can see is I am not sure what position the the cam plate and quadrant should be in when assembling, where the the selector forks go, if that makes sense. Will read up and see if the service sheets give any info.
You need to position the gearbox in neutral. If you look at the LH end of the camplate you will see 5 notches which are the detent positions in the four gears and neutral. The neutral notch is the second from the bottom and basically the two selector fork rollers should be in line with this notch for the gearbox to be in neutral. The RH (outer) selector fork engages with the outer camplate slot and goes down to the layshaft sliding gear. The LH (inner) selector fork engages with the far slot and goes up to the mainshaft sliding gear.
Many thanks, I will try and fit, going to clean inside and what I can get at first whilst the cluster is out .Fingers crossed 🤞I removed the nut and kickstart parts from the shaft before sliding the cluster out should I have left this intact and if so it would be better to connect before sliding cluster back
It's best to assemble everything on the inner timing cover first and check against the parts diagram especially that you've got the shim on the RH end of the layshaft and the washer on the LH end of the mainshaft. I assume the detent spring bolted to the LH wall of the gearbox is ok?
Hi
Really appreciate your help.
Will have a go soon. One last silly question to make it sure for me, when you say LH and RH which direction are looking at the gearbox.
Have a look at this. Not the same bike but principle is the same.
https://youtu.be/SrZTENzk55g
The tricky part is knowing if the reason it won't go fully home is because something isn't right or you're simply not pushing hard enough against the spring at the far end of the gearbox, but a bit of wiggling and jiggling should sort it out.
That channel has some other useful unit construction tips
Quote from: jumbo12 on 01 Aug, 2022, 09:21
Hi
Really appreciate your help.
Will have a go soon. One last silly question to make it sure for me, when you say LH and RH which direction are looking at the gearbox.
Looking towards the front of the bike. LH end means the end closest to the clutch; RH end means closest to the kickstarter.
Hi
Thanks will have a look.
Going to have ago at fitting tomorrow.
One last question, the quadrant part has two prongs and four slots in the corresponding plate, when setting the cam plate like you've explained which two slots out of the four should these prongs be in ?
Surprisingly, in neutral, the two quadrant plungers rest on the camplate itself below and above the lower two slots. In 1st gear, the upper plunger sits in the 2nd slot up but the lower plunger still rests on the camplate below the lower slot. In 2nd gear, the plungers fit inside the bottom slot and the third slot from the bottom.
Hi
Thanks for the update, will have a look tomorrow, thought a British bike would be less complicated than a Jab but maybe not 🤞😭
All 4-speed gearboxes have to do a similar job. However, it definitely gets more complicated when you have 5 or more gears which requires 3 rather than 2 selector forks to try to hook up to a selector drum!
Hi,
Up date on my gearbox problems.
Have had the gearbox in and out a few times now, without any success.
All the parts have been checked and all are in very good working condition lots being new parts.
They are all fitted in the correct positions, the problem seems to be with the quadrant body assembly,
it is working by hand with new springs, the two plungers work, but when the box is assembled and fitted this quadrant part does not seem to want to engage and disengage properly but I cannot see why, there is a little play in the shaft body hole. Sometimes you can engage a gear but not very often. The cam plate is also new and fitted correctly.
Anyone had similar issues or any more comments would be appreciated, not sure what else to check.
Could you explain exactly what happens if you start in neutral and then try to change up or down? What should happen is that one of the plungers should initially drop into one of the camplate cut outs after which exerting pressure on the gear lever should allow the plunger to push the camplate up or down until it indexes the gear. So the question is whether you can see the movement of the camplate by looking at its exposed end or are the quadrant plungers definitely not engaging with the camplate?
Hi
With just the cam plate and quadrant in place and no gears I can turn the cam plate through all the positions going forward or backwards.when all the gears are in place the quadrant plungers seem to stock at various positions. I will have another good look and try looking at what day Saturday.
It sounds as though the gear change mechanism is working correctly with the selector forks removed allowing the camplate to index correctly for all the gears?
Have you tried to exercise the gear change mechanism with everything assembled outside the gearbox on the outer timing cover? I've never tried to do this in this way but, if possible, could give you a better understanding of what is going wrong?
Hi
A frustrated up-date.
Have completely stripped down all gearbox parts again, checked and then re -assembled.
The whole unit does feel better, I can engage all the gears without the selector forks in place when these are fitted I can select some gears, feelsa bit hit and miss, when I re-fit the wholes gear box I can sort of get gears but they are not smooth, perhaps I am expecting it to feel like a Jap box ? Wondering when its fitted with oil, clutch and engine running maybe it will behave differently ?
The only criterion is to be able to reliably select all the the gears in turn (up and down) rotating the shafts when necessary to allow the dogs on the sliding pinions to slide into the cut outs in the adjacent pinions. It's never going to feel smooth doing it without engine running and with no oil in the gearbox!
Hi
Gear selection not really sorted but what I'm going to do is complete the engine rebuild and fit back into the frame and see with the rear wheel and chain fitted if there is any difference
One thing I have noticed is that I thought all BSA gear selection was 1 up and 3 down. I have the cam fitted correctly to the service sheets and manual etc but mine is 1 down and 3 up, is this normal perhaps for a Scrambler?
1 down and 3 up is the way it normally works on most bikes including BSA bikes as this is the most intuitive arrangement. I would definitely get the gearbox working with the engine out of the frame - it won't be any easier once it's fitted.
Hi,
A10s and those using the same gear box and I think other pre-unit gearboxes are 1 up and 3 down.
Dave.
I'd forgotten most pre-unit BSA bikes used the 'race pattern' 1 up / 3 down gearbox shift pattern in contrast with the equivalent Triumph pre-unit bikes that all used normal 1 down / 3 up. The reason BSA went this way may have had something to do with patents rather than trying to make their customers think they were buying race bikes!
Hi
Still struggling with my gearbox problem, checked all the parts and all seems to be ok, can sometimes engage gears when out of engine but only neutral and one gear up when installed. Have noticed that the two plunges seem to engage on the top of the radius corners on the cam plate slots, it is a new cam plate, wondering if the quadrant should be lowered so plungers engage more onto the slot flat faces, I am clutching at straws at the moment for a solution.
Thanks M W
Does your gearbox have the flat positive stop spring? I had a problem with a pattern spring, the bend at the end was too long and would not allow the camplate to move fully, took some finding.
Alan
Hi
Do you mean the leaf spring bolted to the rear of the engine case ?
It is new and does have curve for the cam plate to follow along, if you mean this could you let me know ? then I will check.
Thanks,
Hi,
Yes that is the one, the bent over end was too long stopping full movement of the camplate.
Alan
Quote from: jumbo12 on 30 Aug, 2022, 16:41
Hi
Still struggling with my gearbox problem, checked all the parts and all seems to be ok, can sometimes engage gears when out of engine but only neutral and one gear up when installed. Have noticed that the two plunges seem to engage on the top of the radius corners on the cam plate slots, it is a new cam plate, wondering if the quadrant should be lowered so plungers engage more onto the slot flat faces, I am clutching at straws at the moment for a solution.
Thanks M W
I would have expected the plungers to engage in the middle of the slots in the camplate - that is, halfway between the front and the back of the slots. In this case, are you saying that the plungers engage too near the front of the slots or too near the back? If too near the front, this could well lead to insufficient movement of the camplate when you try to change gear making it difficult for it to index properly -that is, for the detent spring to engage with the notch in the back of the camplate.
Hi
Sorry to ask again but are you saying that the spring was to long overall, if so , if mine seems to long I could try taking some off the bottom edge, did you shorten yours ? Can you member how much excess there was under the radius part ?
Thanks, MW
Hi
With the gearbox out of the engine and on its side with gears etc in a vertical position then if you look at the cam plate from the front with the 5 cut outs in front of you the plungers are engaging at the top end of the 5 slots with some actually catching the radius in each slot , I feel the quadrant / gear lever shaft needs to have some material turned off the under side of the shaft so it drops down and the plungers engage into the centre of each slot on the flat faces. If this is so I cannot understand why unless the cam plate is not as it should be ? Perhaps a badly made one, this could be my problem for not getting the gears !!
Thanks, MW
If I understand you correctly, with the gearbox internals the same way up as they would be in the engine, the quadrant plungers appear to engage too far back in the camplate slots? Any chance of a picture showing the plunger / camplate positioning?
It would be interesting to see the gearbox which might make it much easier to diagnose the problem. Where are you based?
Hi
I am in Sutton Coldfield in the Midlands. I will take a photo soon, a friend has the quadrant at the moment to try and have a look .
Can I attached photos to this site ?
MW
Hi,
The end of the spring where the V is formed was too long and catching on something (can't remember the details it was about 20 years ago).
Quote from: jumbo12 on 31 Aug, 2022, 17:16
Hi
I am in Sutton Coldfield in the Midlands. I will take a photo soon, a friend has the quadrant at the moment to try and have a look .
Can I attached photos to this site ?
MW
I will be travelling back home down the M6/M42/M40 on Saturday morning from the Lake District and would be happy to pop in and have a look at the gearbox if that is any help.
Attaching a picture is simple using the 'Attachment and other options' button. Just need to make sure you resize the number of pixels so the .jpg file size is within the limit indicated.
Hi
If you could pop in on Saturday that would be brilliant, really struggling now. I feel the position of the plungers is not correct.
If you could visit, do you have a mobile or email address that I could give you my address, don't really want to post it.
Thanks, MW
Posting a message on the forum is absolutely secure and I will definitely be the only person who will be able to read it. However, I will post you my mobile number and you can SMS me if you prefer.
Depending on traffic, I should be with you between 11-12 on Saturday. It would be good to start with everything outside the gearbox assembled on to the inner timing cover, if possible.
In the meantime, it would be interesting to know more about the history of the bike and the reason why you have fitted a new camplate? For example, did you acquire the bike in a non-working condition and it's gearbox has never worked properly?
Hi
I purchased the BSA about 3 months ago as an unfinished project.It has had a lot of work and money spent on it. I wanted to strip it down to make sure all was ok as it had been standing for about 2 years. I have only ever been able to engage I think neutral and second gear, I assume on his rebuild is when the cam plate and springs etc were changed. I did ask him the question about the gears and he did say all four gears were working when he rebuilt the bike, do not know if that's the truth, he seemed a decent person.
Since taking out the gearbox I have been able sometimes to engage gears but not consistently.
Look forward to seeing you.
Mike 👍
I'm assuming that the gear change problems were there when you bought the bike - the previous owner may have changed the camplate in order to try to address the issues but this may not have been completely successful.
I'm sure we'll be able to get to the bottom of the problem on Saturday morning. Should be there between 11-12 am and thanks for sending me your details.
Just to summarise what we found when examining the gearbox today. Everything looked ok at first sight after disassembling the gearbox but, when put back into the engine, the gear change mechanism was found to jam and it was impossible to select all the gears. There is a question mark over whether the gear quadrant plungers align with the middle of the camplate cut-out slots and therefore the key dimensions for both components needs to be checked but they are probably ok.
However, after a more detailed look at what was happening when you tried to change gear, the problem appears to be that one of the quadrant plungers was projecting too far, possibly 1 mm more than the other, and was jamming the mechanism. In practice, the mechanism uses the upper plunger when changing up and the lower plunger for changing down. When the gear lever is moved to change gear, the appropriate plunger is pushed against the inside edge of one of the camplate slots thereby rotating the camplate to the next gear position. However, when the gear lever is released, the quadrant spring should rotate the quadrant back to its central position but, to do this, the bevel on the outside of the active plunger must press against the other side of the camplate slot, depressing the plunger and allowing it to slide out of the slot.
In this case, the straight side of the plunger rather than the bevelled part appeared to be hitting the side of the slot stopping it from being pushed out of the way and therefore stopping the quadrant from returning. It's possible, the problem is due to a slightly mangled plunger retaining plate although attempts to bend it to give equal plunger projections proved to be difficult. Short of changing the quadrant, and if it proves difficult to sort out the problem with the retaining plate, it might be possible to carefully grind down the plunger at fault to put the bevel back into the correct position.
Overall, a bit of a strange problem that must have occurred some time ago - perhaps, the previous owner who did most of the restoration work changed the quadrant because the splines had gone and didn't realise the plungers did not sit level?
This appears to be a very subtle problem with this C15 gearbox and the attached picture tries to show the problem in a bit more detail.
The slot marked in red is where the camplate pokes through which is 1/8" in width. The quadrant is in the position it would be in with the gear lever fully pressed down - the flat side of the central plunger will have just pushed against the inside edge of a camplate slot to move the camplate to the next lower gear.
However, under spring pressure, the bevelled edge of the plunger marked in blue will move until it hits the opposite side of the camplate slot. At this point, the plunger should be forced downwards out of the way so that the quadrant can then move back to its central position.
The problem here appeared to be that one of the plungers was projecting too far and, rather than the bevelled edge of the plunger contacting the camplate when trying to return to its central position, the lower straight sided part of the plunger was making contact meaning that it jammed in this position.
The picture shows an easy way to check whether this problem is present because, when the quadrant is rotated by +/- 20 degs, only the bevelled part of the plunges should move across the camplate slot. From the picture, it looks as though it would take a plunger to project about 1 mm more than it should to cause a problem which seems to be case here.
Hi,
If one of the plungers is causing the problem changing gear on one direction then swapping the plungers should also swap the problem. Perhaps worth doing to confirm or eliminate the plunger as the problem. I suppose after that some different plungers??
Dave.
When compared side-by-side, the two plungers appeared to be identical. At the time, I assumed it was the somewhat battered retaining plate that was causing the problem but, in the limited time available, I wasn't able to change the shape of the plate enough to solve the problem. Although its unlikely to be case, its possible the quadrant may have been machined wrongly where the plate screws down and the only solution for this quadrant may be to grind down one of the plungers to make it project the same distance as the other?
Hi,
Update on my gearbox woes!!
I have now fitted a new plate that holds down the quadrant plungers, I have also checked their position from the photo enclosed in the last post regarding the arc they move on the cam plate, one of the plungers was as expected high, I have ground down this plunger and it now fits within the required arc so when trying to engage gears the chamfer pushes the plunger down instead of a dead stop.
Feeling very optimistic as I can now engage all 4 gears whilst applying pressure with my thumb on the cam plate while the cluster is out of the engine.
However, when I fit the gear cluster back into the engine I can engage first, neutral and then a combination of the other 3 gears, I can feel some gears then sometimes a jump from second to forth and so on. Think I just need to keep trying.
I would like to take this opportunity to say what a fantastic site the BSA OWNERS CLUB is, without it and the responsive help from its members especially SPACEMAN, I would not have been able to sort out my problem, fingers crossed.
Regards, MW.
Mike.
It sounds as though your quadrant was machined wrongly because the plungers should project the same amount with a good retaining plate fitted. As discussed, I am happy to send you my spare quadrant to try - if this solves the gear changing problems then it will at least confirm the problems definitely lie with your quadrant which may need a bit more fettling.
However, I am not entirely sure which unit single my quadrant came off although I think it should be ok on a C15. The distance between the shoulders on my quadrant is 1.658" and the length of the splined shaft from the outer shoulder is about 2.863". If you can confirm these dimensions match those on your quadrant, I will stick mine in the post for you tomorrow.
Hi Mike
The shaft length is 2.876 but the quadrant width where the plungers sit is only 1.240 is that where you measured your 1.658 ? If so, not the same quadrant.
But I am not sure if my quadrant is correct for my bike, I've been trying to obtain some dimensions for the correct one but proving to be difficult, the part numbers are all different without any sizes given.
I believe the plunger quadrants are interchangeable on all the side point unit singles (C15-B50). It was the same part number for the B44 through to the B50. Although the C15 has a different part number, I am sure there is only a minor design difference between it and the later quadrants. Unfortunately, Rupert Ratio does not provide any information on the differences.
As said, I am not sure which bike my spare quadrant came off but the key dimensions are shown in the attached picture.
Hi
Checking my quadrant dimensions it is within a few thou of yours so it looks to be same.
If you could send me your spare one to try, it would be most appreciated, might well prove what the problem is
Thanks,. M
I will post it off later today if I get back from my trip in time!
Unfortunately, sorting office closed at 2 pm before I got back and so will post it off this morning!
Apparently Royal Mail is on strike today and tomorrow!!
Hi
Gearbox woes update.
I have now tried another quadrant loaned to me and at last I can engage all 4 gears, sometimes going up or down I do seem to miss one. But it seems to prove that my problem was a faulty quadrant for some reason. Now all I need to do is find another quadrant to purchase , all so far on eBay are all too short. If anyone has a Quadrant for sale please let me know as I cannot proceed with my rebuild until I find one.
Thanks, M
The problem found with jumbo12's gearbox was that one of the gear change quadrant plungers projected too far and this jammed it against the camplate when trying to change gear. This was confirmed when my spare quadrant was tested and worked correctly.
Unfortunately, replacement quadrants appear to be a bit rare on the ground at the moment and so I offered to swap the quadrants. However, the spline on my spare quadrant was not in good condition and so I have undertaken to repair it with a replacement splined shaft. The pictures show the process adopted.
The main issue was to keep the replacement shaft concentric with the remaining quadrant shaft and the way I did that was by boring a hole in the latter on my lathe and then turning a tight fitting spigot on the replacement shaft. The join between the two shaft was positioned so that it would be in the middle of the gap between the inner and outer timing covers.
To perform a strong weld, it was then necessary to machine a groove at the join as shown although this had to be enlarged a bit further to make the welding a bit easier. Even so, trying to weld a small 1/2" shaft was a bit fiddly. After the welding was complete, the shaft was then machined on the lathe to reduce its diameter back to 1/2".
Hopefully the repaired quadrant will solve all of Jumbo12's gear box problems?
Hi,
Excellent illustration of a great repair technique and hats off to Spaceman for persisting in helping jumbo12 with his gear box problem.
This what this Forum and the BSAOC is all about.
The World could learn a few lessons here.
Dave.
Hi
Have now fitted the replacement quadrant supplied to me by SPACEMAN. I can now engage all 4 gears with neutral being a little iffy at times, I feel that when the engine is running, clutch fitted and oil, the gear change will be more normal, not having had a BSA before not too sure what to expect.
Just two other points I would like to make regarding why maybe my original quadrant did not work, they may or may not be relevant.
1. The chamfered part of my original plungers where they make contact with the cam plate are flat, on the exchange one there is a slight radius on this face which I think would help the plungers to work better, less friction.
2. The plunger hole centres on my original quadrant is about 3mm wider than the exchanged one, this may have contributed to why the plungers did not make the correct contact with the cam plate slots for gear change.
Food for thought!!
Once again, I would like to thank the club members especially SPACEMAN, for their time and help on this gear box problem, I would never have sorted it without them and would have reluctantly sold the bike as a non-runner whereas now I can carry on with my restoration.
Members please carry-on helping others as you do, we all appreciate your comments and experience.
Regards, M
Having had a chance to have a good look at the old quadrant, the problem now seems to be that the bore for one of the plungers is very rough and the friction produced makes it very difficult for the plunger to be pushed out of the way when it comes into contact with the camplate.
The quadrant has clearly been abused in the past because the retainer plate was very battered. I need to look more closely but the rough bore seems to be scored internally circumferentially. It's possible the plunger rusted inside the bore at some point and some hammer blows were applied to the plunger in order to free it producing the scoring.
I am sure it is repairable but am not sure how at the moment?