The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: KiwiGF on 12.06. 2012 12:43
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My 56 STD s/a box for my GF has a few chips on the first gear on the mainshaft and I was looking to use a gear from a spare plunger box I have, which I think is a 49.
The 2 gears look the same apart from the plunger box has every other tooth ground down/relieved where it locates in the adjacent gear. I guess this may be to improve selection but it does seem to be at the expense of strength.
My questions are... is it ok to fit the first gear from the plunger box? Is one gear design better than the other? I'm not sure that either box has the original gears in it.
I could post photos if needed.
Thanks in advance.
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Hiya kiwi,
Not sure 'bout the 'relieved/ground down' maybe post a picture??
Seems the '49-'57 plunger and S/A gears(std 27 T) are same part#, maybe '49 is a crossover year and some reason a bit different , but can't see why it wouldn't work at least to get you out of trouble??
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Hi Dutch, I'll post a pic later today when I get home. The teeth are relieved/ground away much more on the gear from the 49 box, such that only half the teeth engage "inside" the adjacent gear. My concern is based around the fact that I've read that early boxes had problems and the design was improved by BSA as a result, and I don't want to use one of the components that needed to be improved!
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Kiwi,
The gearsets from the early boxes are completely different to about post '51 boxes.
Trev.
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Thanks Trev, I am interested in whether its a late or early plunger box mate might want this box for his longstroke. From what you say it's a late box and it won't be any use to him. I got the idea (probably wrongly) it was a 49 box from a part number on the selector forks being 67-3118 as opposed to the later 67-3204. From my experience to date of my bike and the parts it came with I would not necessarily rely on any part being what it seems at first.....the plunger box might have the wrong selector forks (or gears) in it!
The plunger box I have has a splined not keyed mainshaft (clutch end) the selector mechanism is very different design to the s/a box as well. The output gear is different on plunger box, but a couple of the other gears including bottom gear look like they will fit the s/a box - hence my question regarding the bottom gear.
One of the other plunger box gears I have already swapped over as it was identical to the equvalent s/a gear, other than what I think were material spec. markings "EN" versus "V".
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Hi Kiwi,
I think I know what you mean, the 'dog' part of the gear, it being similar to the sliding gear at the sprocket end that engages with the mainshaft sleeve gear?
My info was looking at a spare Plunger gear cluster I have-(less mainshaft w. 1st gear), and as per parts books, and probably Trev is more able to help here, as I've had nothing to do with the earlier boxes, so'll quit whilst ahead...ish... ;) ...
Cheers,duTch
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List of parts and pinions here http://www.draganfly.co.uk/shop/pi1445653175.htm?categoryId=686 (http://www.draganfly.co.uk/shop/pi1445653175.htm?categoryId=686)
From the list you can see what is compatible
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Pics as promised. Oddly both boxes have forks with 67-3118 on them, maybe that's a casting number as it does not line up with my parts book or Draganfly.
Anyway hopefully the pics show the difference between the 2 bottom gears, hopefully someone will know if the gear in better condition (on the right) is OK to fit in s/a box.
In the "exploded" pic the plunger box is on the left.
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Yo Kiwi,
I see what you mean,much as I thought, but more pronounced. Can't see why they won't work, put em in and see if they make funny noises on the bench???? then on the road??
I know the RRT2 gears are totally different,and you'll see why if you have them, and maybe scramblers?
Shifter forks are listed as part #67-3204 for s/a & plunger 49 on,so whatever they're stamped maybe as you you say(cast #?) and if they fit and do the job....?. Spare ones I have are also stamped 67-3118 and do the job.
Otherwise see what others have to say????
cheers for now
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Thanks everyone, I had a good look at all the gears again tonight in the knowledge the part numbers were largely unchanged between the boxes and have come the conclusion the differences in design is just another of those little changes bsa made over the years and not related to the early box issues I'd heard about
One of the other gears had similar differences to the bottom gear, and the dogs were also altered in shape on one other gear as well, all with the same part numbers.
Overall I'll be better off with the plunger bottom gear I reckon so that's going in.
Its not a huge job to swap out the gears if the changing is no good!
Thats assuming i can figure out how to put the clusters back in, it looks like one of those "knack" jobs...easy .....once one works out how to do it.
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While the cut on the teeth changed you can mix & match provided that you do it in pairs so you put both the plunger main shaft & lay shaft gears into the swing arm box.
As Trev noted earlier they are different so a plunger gear on the main & a SW on the lay will give you grief.
Also have a close look at the dogs .
When I have made an almost acceptable box from a bunch of buggered ones I some times need to play with thrust washers thicknesses or take a bit off the end of some dogs so that they can engage fully.
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Thanks Trevor, I will be fitting both gears it seems to make sense for a number of reasons but I'm stumped to see a noticeable difference between them other than the dog part of the teeth!
I'm just glad I could could get some use out an old box which I think is one of parts one can call "sale proof" in nz.
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Hi Kiwi,
Been away for a week or so,
In my opinion/experience ????
The early gears have half the number of dogs to take the drive the later have long and short , this helps with gear selection, and then the short provide more strength when fully engaged
I'm guessing BSA found a need for this on the bigger cc bikes as they continued with the early type gear on the 250cc models fitted with the heavyweight box (or maybe use up remaining stocks??)
I have also found that later boxes have gears stamped EN36 and earlier?? V18 or VIB
see this prevoius posting
http://www.a7a10.net/forum/index.php/topic,4817.0.html
Hope this helps
John
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Thanks John, there's more to the interchangeability question than I thought.
But the box build is on hold due my own stupidity! I ruined the Rh end mainshaft thread after the shaft got stuck in the smaller ball bearing in the inner cover, when I was trying to fit the inner cover after getting the mainshaft and layshaft all in place. The shaft was far to tight a fit in the bearing especially as the inner appears to be clamped by the nut and kickstart mechanism on the rhs end anyway. Should they be a typical interference fit?
I'm not sure if the bearing was at fault or the shaft but I'll test fit them together next time and once I have found a new mainshaft. Expensive mistake on my part :-(
Another question ......is the best way of assembling the box to fit the inner cover/bearing once the mainshaft is in position in the box? or fit the cover/bearing to the shaft, and then fit the whole lot together?
Hope that makes sense!
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Hi Kiwi,
Bummer about the shaft *sad2* *sad2*
OK heres another of my ?0.02 worth
The shaft should be a light press / tap fit in the bearing, the outer ratchet nut MUST NOT be over tightened as this will distort the ratchet bush
I fit all the innards before fitting the outer cover (works for me!!)
HTH
John O R
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Yeah Kiwi bugga 'bout the shaft, but don't ditch it threads can be redeemed... maybe?
As John says/inferred, nice snug fit sounds good, I had a little grief wit mine too when I reassembled, just gotta go steady steady. I think personal choice on the reassembly, mine being Bolt-on, put the guts in place then pulled the mainshaft out to put in the inner cover bearing, and jiggled back together, but yours is S/A. Just make sure you get the index marks right as discussed a little while back, not hard, steady steady.
cheers duTch
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Thanks John/Dutch - this confirms what I suspected, this being the shaft should not have been as tight in the bearing as it was. I managed to crack the shaft where the thread/kickstart spline is *sad2*.
If I was was desperate the shaft could be fixed but it would be a "mission". I've ordered a used one from a local supplier and fingers crossed it's in good enough condition to use (tapers and key slots tend to be knackered on them of course...). I should know it's condition when I get home tonight.
I've made a right mess of the fixing up the box! I fitted/reamed new sleeve gear bushes but am I'm now having to use the plunger box sleeve gear to pair up with the better condition plunger L/S gear, as per above posted advice - so I might be waiting for parts and re-doing the sleeve gear bushes again.
I just hope I get my act together once I get the engine parts back from the machinest....(fixing mismatched cases, oversize plain main bearing housing, distorted barrel bottom face, bad threads etc). I'm still planning to have the bike ready for next March's National BSA rally in the Wairarapa (especially as I am helping in the organisation of the rally). That's not a very difficult target....... one would think! (but my original target was LAST years rally, in Dunedin).
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Kiwi,
Just a thought- I presume you have the correct (imperial size) bearing? Don't know how close a metric one is to size, could be close enough either way to cause grief?
cheers
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Hi Dutch I'll measure the various parts up and report back, I guess a thou might make all the difference.
The local supplier sent me a mainshaft off another bike, I'm not sure if they can supply the right one but I'm not holding my breath! *rant* *rant*
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The bearing should have a number on it, if you didn't replace it and it was correct to start,-reckon it should've gone back in ok!!??
But as I said I had a similar moment with mine but can't remember what I did(fairly sure I put a new bearing even though old one was ok??)
Just don't go blue like those little ranty blokes!! tho' they are entertaining
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Dutch, bearing is new from Draganfly in box with L 3/4" on it but I will measure it and the 2 shafts etc
I suspect I need a new bearing as it was well and truly stuck on the shaft and I've probably marked the track. Blue fellahs are great. Discovered tonight. Yep I feel a bit annoyed , myself to blame with cost if new shaft I might go for using the plunger shaft and non BSA clutch
Painful given all the new 6 spring clutch parts I've already bought!
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Hi Kiwi, I experienced the same problem last year doing my box up. The mainshaft would only fit through that bearing after i used considerable force ,block of wood and hammer no damage to shaft but once just about together couldn't tighten cover and still turn layshaft ,turned out to be an oversize mainshaft , rub was the mainshaft was new and from Dragonfly. During the numerous attempts to rebuild the box I came up with a way of keeping everything together, simply use a rubberband to hold cogs and gearchange dogs together both main and layshaft, worked a dream . You remove the bands via the inspection plate in the side and long nosed pliers carefully.As per Dutch's post watch the dots on the inner cover and gearchange pawl ,normally dotted red ,that also caused me grief for ages until someone( wonderful person) on the forum suggested moving the dots slightly out of line ,Mine was a teabreak box and that did it been great since, best of luck BobH
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I just remembered I have info stashed in my phone in front of me;- Hoping what I have is the correct info, anyone else can please confirm??
# RLS-6 1-7/8 x 3/4 x 9/16 That could be the bearing shop P#, but it should still cross refer.
Don't get carried away with the 'Rantys' like I do.
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Hi Kiwi,
I'm trying to keep pace with all the changes you are making *conf*
To the best of my knowledge the inner engagement dogs on the plunger sleeve gear are different to the swing arm sleeve gear , ( I hope I'm wrong for your sakes ????)
if this is so then you would need to change the 3rd gear pair as well
(if that will work out with the engagement dogs on the opposite side ????)
More and more *conf*
On the other hand I have seen gearboxes running away merrily with a lot of wear on the gear teeth faces
and I have fitted NOS gear pairs which whine like a banshee ????
Gook luck
John O R
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Hi Dutch/John, I'll report back after a good look at things tonight. Recognise the incorrect shaft I was sent by any chance? Its the shorter one in the pic....
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Hi, I've had a look with the benefit of all the info in postings and found:
1. The mainshaft I broke is at least a thou more in diameter than the other two mainshafts I have at 0.751" and that would have caused the problem with fitting it I think, maybe same as yours Topdad? The new bearing it was supposed to fit into is the same inside dia as others I have at 0.750" maybe less a bit.
2. Of the 8 gears only one seems to be too different to fit in both boxes, plunger or s/a, that being the l/s gear nearest the clutch that engages with the sleeve gear has slightly different dogs, but even that gear looks to be only different due to the plunger l/s being slightly different, or in other words fit a plunger l/s in a s/a box and that gear would also fit in a s/a box.
3. So the gears marked v16 (from plunger box) look interchangable to those marked en36 (from s/a box) but given advice to the contrary that are not a compatible material or shape I'm not going to mix and match v16 and en36 gears, but I sure could understand people giving that a go!
I'll post pics in due course of the gears/shafts.
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So heres a pic of one side of all the gears, on the left the gears and 2 shafts taken from a plunger "semi unit" box, the gears are marked with V16 albeit some markings are incomplete. On the right are gears and shafts taken from a 56 swing arm box most of which are marked EN36. The far left has the layshaft gears from the plunger box. I've shown just the "dog" side of the gears as the other sides all appear identical.
So the visual differences are:
1. The layshafts have the wire spring clip in different places on the shaft, this means the gear kept in place by the clip will not fit on both layshafts. The inside of the gears dogs are machined away on the plunger gear to allow the gear to slide further over the clip. My guess is the s/a design is stronger as more gear engages with the hex shaft. Without trying it I would say the plunger layshaft and that gear would fit into a s/a box, if one really needed to use that gear, but see below ref lube provision for the plunger layshaft. There's a close pic of the end of the shafts showing the difference (pic 227), also a close up of the inside of the 2 different gears (pic 224).
2. The plunger layshaft does not have a spiral groove for the drive side bush. The bush also does not spiral groove either box, I guess the groove on the s/a shaft is to improve the life of the bearing, the bush in the plunger box has a longitudenal slot I guess in place of a spiral on the shaft. the s/a bush does not have this cutaway.
3. The dogs are different on two of the plunger gears, the m/s gear next to the sleeve gear, and the l/s bottom gear. There's a pic of the bottom gear in an earlier post and the other gear from each box are in pics below (pic 225 and 226). My guess is these changes in design are to increase strength rather than gear changing but I could be wrong, the design change did not appear to require a change in design of the gear the dogs engage with (this assumes the boxes I a have contain original gears of course!).
4. The washers on the layshaft are of different thickness, though I'm not sure if that is caused by wear, or to get the end float correct.
Anyway, I hope all these posts that adds to the forum knowledge and helps someone.
My problem (edit: now all answered/solved thanks all) has now switched from being whether to use a V16 bottom gear in a s/a box (it is has slightly different dog design to the EN36 gear) to sourcing a new mainshaft (or maybe I'll use the plunger mainshaft and spend the money on a better clutch instead).
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Hi Kiwi,
First thing that came to mind is, wouldn't the 'engagement factor' still be governed/determined by the 'throw' of the selector forks??
Otherwise my attention span at the mo' is kind of short-had a big night last night, but maybe can suggest slipping in the images next to the description, might save scrolling up'n down ??
Cheers for now duTch
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High Dutch, I'll see what I can do ref pics but I just added them at the end, no obvious choice on position but I'll work on it.
Engagement factor if I understand that correctly is the same either gear, but with en36 gears its not just the dogs that engage but the other teeth as well? which is stronger, if that makes sense?
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I'll see what I can do ref pics
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