The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: Mosin on 06.07. 2009 12:07
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I have now covered about ten miles on my A7SS, but for the life of me I can only seem to find three gears in the box! The speedo doesn't seem to be working very well and is not accurate and I have mostly been riding down very narrow country lanes where it can be difficult to guage exactly what speed I am doing, so it is not easy to tell what gears I am getting. I have checked the gearbox oil and that is fine and the clutch etc seems to be working well, but the box is still very clunky, only allowing me to drop from what I think is second, down through neutral to first when the engine is running very slowly. My instinct is that I am not getting top as The engine seems very revvy when I am in the highest gear I can find, but without getting out onto a main road, it is difficult to be sure. Especially since I have never ridden an A7SS before and have nothing to compare it to. Unfortunately, My bike does not have an MOT and the nearest test centre is 25 miles away and I'd rather not ride this without top gear! Hmmm.
Any suggestions for things to check would be most welcome.
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Mosin,
At the risk of horribly underestimating your experience, I apologize in advance, however, it sounds like you are starting out in 2nd gear (down one stop from neutral), which would explain slow engine on take-off. First gear is upward from neutral (sorry if this is way beneath your understanding). Depending on the chain sprockets on the engine and gearbox, 4th gear (1:1 ratio) can feel like a rather low gear for the open road. My 4th gear is a bit like this. I am yet to try real road speeds of 65+ mph, as my engine is yet to complete the break-in period. If your gearbox has "Sc" stamped on top, it is a scrambles type and 1st, 2nd and 3rd gears are lower ratios than a standard gearbox.
All of the above said, there may be a problem in your gearbox which might, from your story, be recognized by someone having more experinece than I.
Well, now, I'm just guessing and others will put me in my place for my "misguided ideas," but it also sounds to me like, either, your shift pedal is on backwards or you have a rear-set shifter cam plate (inside the gearbox) with a front-set pedal.
Boys, straighten us out!
The discussion got me thinking again about ratios, so, I went looking for this chart in our fourm. http://www.a7a10.net/forum/index.php?action=dlattach;topic=325.0;attach=465;image
Part of the point is how great the forum is in keeping our precious information resources. I went to the search tab and entered "gearbox chart" and "Match All Words" and, presto, there it is!
Regards,
Richard L.
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The gears on my machine were difficult to engage after re build. I found that I had the cam plate plunger screwed in too far. I kept unscrewing it half tun at a time with the bike on the stand, until the gears selected more easy. Might be worn checking.
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Mosin,
Here are 2 rather obvious questions.
a) ,has this g/box just been rebuilt and
b) Are the timing marks on the quadrant aligned correctly ?
As described in the Haynes manual.
Mike
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Hello
I have just spent a long time sorting my box, and just to put a very hard earned piece of information forward, my box would not shift correctly with the two dots aligned, but rather with the one on the quadrant one notch down. Took many test fits to figure out... Now everything is sweet again.
Otto in Denmark
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OK, Thanks for all the tips guys. I have now had the A7 out on the open road and am now convinced that it is top gear which I cannot find. I am selecting first ok (one notch up from neutral) and then dropping down into second, then down again into third, but after that I am hitting a stop. The engine runs beautifully up to about 50/55 in the highest get I can find (which I think is third), but then it runs out of power, is revving like mad, and is crying out for another gear.
I decided to have a look at the Cam plate plunger as it seemed the easiest thing to start with, but both it and its locking nut are siezed absolutely solid and they are not the easiest things to get at. I am at a serious risk of rounding off the corners if I apply any more force to them. Something which I don't want to do.
MY gearbox has "STD" stamped into the top of it. I assume that this means it is a standard box.
I do not know if the gearbox has been rebuilt or not as I bought the bike on ebay and got very little information about it. But it is increasingly looking as though the gearbox is going to have to come out of it while I investigate things further (and also free up the siezed Cam plate plunger). I have never taken a box out of a bike before.
Is it relatively straightforward? Does the engine also need to come out? Is there anything in particular that I need to know before I start? Is there anything else I can try before I resort to removing the box from the bike?
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Mosin,
You can examine the contents of the gearbox without removing it ,or the engine.
You can pull most of the internals out from the r/h side.If you want to remove the mainshaft or get to the sprocket and main bearing then you will have to remove the primary (l/h)drive side .Chain-case clutch and chain etc.
It is straightfoward.Follow the directions in your manual.
Mike
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I would look at the "timing" as Otto mentions. The lining up of the dots is a little hit and miss.
Take the outer cover off and try to select the gears with a screwdriver or some type of lever and see what you get. If the box is out one tooth you will find that the selector fouls the slot in the inner cover and will not move far enough to select top gear.
Trev.
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Well I opened up the gearbox this afternoon, as suggested, and found the mark on the quadrant to be miles off the mark on the casing. Assuming that I had found the problem I lined them up perfectly, reassembled the lot, filled it with oil and took the bike for a spin. Hey-presto, I now have only TWO useable gears! Second and Third. Once it's cooled down a bit, I'll try it as Otto suggests with the quadrant one notch down and see what happens. Why is nothing ever simple?
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This is how the dot alignment looks on my box when gears are indexed correctly:
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Why is nothing ever simple?
Mosin... It is simple!........... when you know how! I almost guarantee that when you get this sorted, you'll know for next time and probably will be advising the next person who has your problem. *smile*
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Hey-presto, I now have only TWO useable gears!
Ahhh, nothing compares to the joys of owning and restoring old machinery *smile*
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Having now dissassembled and reassembled the b*%^&y thing about fifteen times today, I finally took it out for a spin. The gearbox was jumping all over the place, particularly out of gear, and the clutch for some reason started slipping like mad, but I am pretty certain that at various times on the ride I managed to attain all four gears; A first! Unfortunately before I was able to set up the clutch and try it again, my wife reminded me that I have a 10 month old baby who hadn't seen me all day....
Oh well, I'll have another look at it tomorrow...
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I would suggest the boring but thorough way; take the whole box out, and take it all apart, to inspect the gears. It is easier to check new settings when the box is in a vice also. Then you know what you have. You can get gearbox parts fairly easily on eBay. I know what you're going through! I was there a month ago, but the stuff does work when assembled correctly. If all bushings are worn it would add to the general malfunction of things, but this can be fixed by simple replacement - even if it is a lot of work.
Otto in Denmark
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Success! (in part).
Well, I now finally have all four gears, plus neutral, selecting very positively and all is looking good (This was finally achieved by positioning the mark on the quadrant two notches above the mark on the casing). Anyway, delighted with myself, I put the whole thing back to gether and went for a spin only to find that the clutch has suddenly started slipping like mad as soon as it is under any load at all. This is something which it never did when I only has three gears. I tried backing it off on the adjuster tight to the point where it was actually dragging as I was stationary and in gear with the lever held right in, but it was still slipping under load. Sorry for being a pain, but can anyone offer any explanation for this, and more significantly, any possible solutions?
Many thanks
Simon
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Your clutch is now dragging because ,as you say ,you have loosened the adjuster off too much and so now you dont have enough pull on the lever.
So next,remove chaincase and check and adjust the pressure plate spring adjusters (you could have 5,4 or 3 springs depending on which clutch you have ).If they are all right, then undo them and pull out all the clutch-plates and check the friction plates for wear (lack of friction material).
Also check plates are not "hanging up" (unlikely)and are actually being compressed by the pressure plate
When Ive worked on clutches I often go for a short ride to try it out before re-fitting the chain case.You can rest your left foot on the pillion f/rest to keep it clear of the chain.
Mike
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1) go to ATF in the primary
2) clutch plates oily ?
3) clutch springs too weak or binding.
4) cage or center with deep notches
5) hub not seated properly and spinning on mainshaft
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I'll give it a go..... What could possible go wrong.....?
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Well, I have now had my clutch to bits as suggested. Because I have never worked on one before, I don't really have anything to compare it too in terms of wear on the friction plates. However, none of the plates were oily and the springs were all the same length. I tightened the springs each one in turn to ensure a uniform pressure and I now have the clutch so tight that I can only just pull it in at the lever but it is still slipping when under load. Incidentally, it has six springs. At low speed/revs it seems to be working ok and it is engaging fine (even though it is very stiff) it just seems to be slipping under load. I am inclined to think that it is probably not simply a case of wear on the friction plates as it was working fine before I started messing with the gearbox.
I am now getting very frustrated with it having spent the past three hours riding it up and down the road with my left fut on the pillion peg and the chaincase off stopping every couple of hundred yards to adjust all the nuts or the push rod. None of which have left me feeling as though I am getting any closer to actually making the thing work again.
Any suggestions would be most welcome.
Simon
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This may be a silly question, have you checked that the shaft key is still intact?
I have seen this problem on an A65 with the key sheared off.
Trev.
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Trev,
I have had a look at the exploded diagram in my Haynes manual and I can't see any mentio of a shaft key. Perhaps the A65 is slightly different?
Simon
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The clutch set up is the same for every BSA ever made with the exception of the Bantam and the bolt on gearboxes both of which have a splined mainshaft.
There is a key.
Its purpose is to index the hub to the main shaft and to prevent the hub turning on the mainshaft when you tighten the clutch nut.
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I've found the key! It was on the gearbox diagram in Haynes rather than on the clutch diagram! I have also found it on the bike and it appears to be completely intact.
However... I did notice that some of the "fins" on the Clutch chainwheel which form the housing for the clutch plates appear to be bent outwards slightly i.e. they are not at ninety degrees to the chainwheel itself. I suspect that this may possibly be my problem because they appear to be allowing the plates to rotate within them rather than gripping. Does this sound like it might be possible? Also, is it permissable just to have a go at bending these "fins" back up to ninety degrees to the chainwheel or am I looking at having to buy a new chainwheel? Finally, Haynes is showing some sort of shroud which appears to go around the outside of these fins (presumably to prevent ATF from making it onto the plates) My bike does not appear to have any sort of shroud like this. Is this likely to be a problem?
Simon
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Mosin,
You could straighten out those fingers yourself and, if careful to get them all at 90 deg. to the chain wheel, you should be good. Examine the slots between the fingers where the plates fit. These must be free of nicks and gouges, any found should be filed out, leaving a nice clean edge along the slot. Otherwise, buy a new pattern basket for around 35 GBP. The one I bought was not great, but OK, the problem was that one or two studs spun where they were pressed into the basket. the fix was to braze them all in place. Maybe a first-rate N.O.S. basket would not have that problem, but I didn't know where to get one.
Richard L
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Simon,
you must have an early basket. Later ones have a band around the outside to prevent what has happened to yours.
You could straighten it and modify it with a strip of sheet metal tacked to the outer diameter.
Trev.
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Trev,
Perhaps I read too fast. I thought Mosin was talking about the inner basket. Nevetheless, I think what I suggested still applies, except, of course, regarding the studs. Very interesting about the early baskets not having the band.
Mosin,
Are talking about the tines for fitting the inner tabs of the plain steel plates or the outer tabs of the friction plates.
Richard L.
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Sorry, I am talking about the outer basket. The one with the slots for fitting the outer tabs of the friction plates. The tines which form these slots were splayed outwards by a few degrees - probably due to the absence of this strip of metal which Trev mentions. This appears to mean that only the innermost friction plates are actually engaging with these slots and the outer ones are rotating freely within the basket. I have carefully bent the tines back up to ninety degrees and reassembled the whole thing. I will give it a go when I get back from work today, but I am cautiously optimistic.....
Mind you, I've said that before....
Simon
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Well, I've had the bike out for a spin and the good news is that the clutch started off working perfectly! The bad news is that after about two miles the fins/fingers/tines/whateveryouwanttocallem had splayed back out and the pressure plates were spinning freely in the basket again with all the clutch-slipping consequenses.
So, now I know what the problem is and it looks like I'll be ringing round tomorrow to see who can sell me a new clutch chain wheel. Preferably one with a metal band on it to prevent this happening again.
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Just by way of a follow up, I got hold of a NOS clutch basket off ebay (one with a band around it) and I fitted it yesterday. It works absolutely fine. So now I finally have four working gears and a working clutch! All I need is for it to stop raining for five minutes and it's off the the MOT Test Centre for me!
Thanks for all the help guys. I would have been completely lost without it.
Simon
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Hi Simon,
Glad to hear all is well again,
Did you check the tangs on the plates that engage with the chainwheel for damage?
If they were skipping on the old one they might have been rounded off! they should have sharp corners and the plates should be a reasonably close fit in the basket
Regards
John O R
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Hi John,
Some of the tangs on the friction plates were a little rounded on the leading corners of the tangs. I overcame this by simply rotating the plates through 180 degrees when reassembled the clutch so that the damaged corners were not taking the same impact and, what had previously been the undamaged following corners of the tangs, are now forming the leading edge. I hope that this makes sense (basically, I just put the friction plates back on the other way round).
I don't know if this is an acceptable solution or not, but it appears to be working so far....
Simon