The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: owain on 14.09. 2017 16:32
-
Righto, I've had this problem for a while now and I can't seem to find a solution. The issue is that I'm losing transmission at high revs i.e. it feels like the clutch is slipping. I've fitted new friction plates into the clutch and clutch was nice and dry when I inspected it. The clutch springs are set really tight. A few more turns on the spring nuts and the springs would be completely compressed. The shock absorber spring nut is on tight and the spring is fully compressed. I'm scratching my head as to what the problem is. Any ideas would be appreciated! Cheers
-
Hi owain,
check the sideplay of your cluthrod. There must be a non working space about 1,5 mm at the rod befor the plates lift.
cheers Klaus
-
Have you done anything to your clutch lately
-
Cheers Klaus, will have a look if there is a gap on the clutch push rod.
Yeh, the bike has had a full mechanical restoration (bought it as a running basket case) i.e. crank grinded. oversized bore. replaced damaged gear sprockets. no new parts for the clutch though except for new friction plates. Difficult to say whether that is to blame as I didn't ride it with the old friction plates on.
-
I'd like to give a solution, but can't but let's specify here that I believe yours is a 6 Spring Plunger clutch, and mine also does it sometimes but only under load if I give it some...
I also can't get any more spring preload than you for the same reason (just short of coil binding). I had five friction plates in as per list, but I wasn't happy with the minimal engagement of the adjuster nuts, left one out last time and swap one out/one in each time I have it apart...
The only thing I can think of is the springs may have to many winds (too soft)
-
Have you tried using ATF ? Dexron allows some slippage but Ford F type gives a much more positive grip.
-
Are these different types of friction plate? (ford f type, ATF, etc). I'm not sure the specs of the friction plates fitted, I bought them from Draganfly though..
Yeah it's a 6 spring clutch dutch. It certainly is under load as it's pulling a heavy sidecar as well. Haven't even dared taking it up any hills either (currently in mountainous North Wales)
-
G'day owain.
RorC refers to Automatic Transmission Fluid of the Ford F type.
What oil do you have in the primary? If it's a multigrade car oil it will have friction modifiers that will cause slippage.
Cheers
-
Wear on the chain wheel and inner clutch basket can cause clutch plates to stick and clutch to drag and slip, no amount of spring pressure will overcome that problem, a file taken to make the surfaces smooth again can be used to fix that up.
It sounds like you have had to compress the springs too much, this should be making it really hard to pull the clutch lever in! If not I would suspect incorrect springs.
Note even with some free play in the clutch cable when the engine is cold, this can disappear when it's hot and even a small error in adjustment this can cause slip.
Some of the cheaper all metal clutch plates are made too thin and can can cause problems. They should be around 1.6mm thick from memory.
-
some clutches require a plain plate to be put in first to take up play as the first friction pale will not reach the base of the clutch basket ( the tangs stop it going in far enough), If I recall correctly I also think the usual BSA diagram used in many places has the plates in the wrong order, this mat be one and the same thing.
This might explain why it drives at low revs and slips at high
-
.. but let's specify here that I believe yours is a 6 Spring Plunger clutch, ...
*????*
Before we get carried away, let's confirm that it's a Plunger six spring clutch, which is a completely different animal to swing-arm six spring clutch (emphasis on 'animal')...?
-
Looks like a plunger in Owain's picture . So should be a great clutch ,well up to dealing with a mere double sidecar. By the way Owain how the hell do you miss hills/mountains in north wales ??? where are you at the moment .cheers Bob
-
Yep, can confirm that it is 6 spring plunger clutch. I'm going to remove the clutch plates, measure the spring length and file the inner basket to make sure that all the friction and plane plates can travel freely i.e. don't jam up.
Haha I'm severely limited to the promenade in Llandudno ;D
-
Righto, I've taken all the clutch plates out there are 4x 1.6mm thick plain plates and 1x 3mm thick plain plate as well as 5 friction plates. Springs measure approx 36mm in length. I'm using 20w/50 mineral oil in the transmission case...but it's a dry clutch so I wouldn't expect oil to be the culprit if the clutch is staying dry.
I lightly filed the clutch plate 'tracks' in the inner and outer clutch basket. Removed some muck that was on the clutch basket wall. Degreased it all then applied a thin layer of lithium grease into each clutch plate track. I thought this last step might be a bit risky as I don't think grease on the clutch plates would be particularly helpful but I applied it carefully so that it is only a thin layer in the tracks only. My rationale was that it should facilitate the free movement of the clutch plates when pulling the clutch lever in.
Everything is back on now and so I'm gonna go and menace the pensioners on the prom with a lot of throttle. ;)
-
No luck. Still slipping. Quite hairy when I'm pulling out of junctions. Slips a lot.
-
Did you say there is pushrod free play?
If the stack of plates isn't thick enough, the pressure plate can hit the clutch centre before the plates are fully compressed. At least the later 4 and 3 spring clutches can do that and the plunger 6 spring looks like it could.
-
Ah good point Triton Thrasher. Yep, there is free play with the pushrod. I've played around with it quite bit but it doesn't solve anything unfortunately. I'll have to take the clutch apart again tomorrow and have a look for wear on the back of the pressure plate. What would the solution be though? Extra friction plate maybe?
Does anyone know whether there are supposed to be any friction 'pads' on the bottom of the chainwheel? When I look at SRMs chainwheel for a A7/A10 plunger, it seems to have friction pads on it. Mine doesn't have any there..
http://shop.srmclassicbikes.com/product/chainwheel-6-spring-inserts-a7-a10
-
Hi Owain,
That's a swing arm 6 spring chain wheel not a plunger one
Check for distorted plain plates if you dismantle the clutch
John
-
Ah yeh, so it is chaterlea25.
I think you were onto to something there Triton Thrasher. I just checked the service book diagram of the plunger clutch and I have correct plain plates...but I'm missing one friction plate. The pressure plate is sitting directly onto a plain plate. It seems very simple in hindsight! *doh*
-
G'day owain.
The pressure plate acts against a plain plate. 6 plain (the rear one is thicker), 5 friction plates.
The domed cover is to keep most of the oil out but a little does get in. If you use a multigrade oil make it a motorcycle specific type OK for wet clutches. Castrol Active 4T, Shell Advance AX5, Penrite MC-4ST or as others here ATF F type. If you have surflex friction plates they can run wet (cover off). Your friction plates may have been contaminated with the modifiers in the oil you used. A good soaking in petrol the dry and give them (both plain & friction) a light rub on a flat surface (glass) with 400 grit wet & dry. Grease is not a good idea in there.
Another quick fix is to put 1 or 2 flat washers under the springs in the cups. When tightening the nuts keep the studs just below the surface of the nuts and make sure the pressure plate lifts squarely https://www.a7a10.net/forum/index.php?topic=564.msg50805#msg50805
Cheers
I luv my plunger clutch.
-
I'm not sure of the standard length the springs shoud be, but from memory I think mine are all about ~1,1/2" ( ~37mm), so yours may be a bit short and lost pressure. Being in Wales, you may be able to squeeze in a trip to SRM....
I bought some new springs from ********, and they are wound the opposite of what came out, which may or may not matter so I haven't used 'em- but that's a different issue
PS; I don't recall seeing any mention of you trip from the Continent but congrats you got it together and so far *good3*
-
Ah yeh, so it is chaterlea25.
I think you were onto to something there Triton Thrasher. I just checked the service book diagram of the plunger clutch and I have correct plain plates...but I'm missing one friction plate. The pressure plate is sitting directly onto a plain plate. It seems very simple in hindsight! *doh*
I don't know these clutches well, but the pressure plate is either kissing the clutch centre or it isn't. If you remove one plain plate and the pressure plate can still press the plates together in a trial assembly, then that isn't the problem.
When you said it slips when you take off from a junction, that sounds so bad that it seems it must be something worse than spring pressure being a bit light, or a little oil on the plates. That's what made me try to think of a positive mechanical reason.
Is the handlebar lever quite light to pull?
On a three spring clutch on another well-known make of twin, my Surflex plates always slipped if any oil at all got on them. Re-lining them with cork matting and squeezing an extra pair of plates in fixed it. Cork seems to be very good in wet clutches. Yes I know- yours isn't wet.
-
Not disputing what you say TT, but attached is a pic of my spare Plunger Clutch basket (complete with crusty phosphoric acid residue), but no springs, cups or plates
Can be seen how low the pressure plate sits in the main basket.
.... I think you were onto to something there Triton Thrasher. I just checked the service book diagram of the plunger clutch and I have correct plain plates...but I'm missing one friction plate. The pressure plate is sitting directly onto a plain plate. It seems very simple in hindsight! *doh*
I don't think that's a problem;
As Musky says the pressure plate is against a plain plate, which I maybe wasn't aware of when I dropped one friction plate out but figured it doesn't matter as they both run in the same splines so can't spin or go anywhere anyway...so going on that, I must have 5 plain plates (including the thick rear one)- fairly sure...
-
Hey Dutch- you are disputing what I say and you're quite right. It looks impossible for the pressure plate to foul the centre, in that clutch.
Are they all as deeply dished as that?
-
Do the spring cups ever bottom out on these things?
-
I bought some new springs from ********, and they are wound the opposite of what came out, which may or may not matter so I haven't used 'em- but that's a different issue
PS; I don't recall seeing any mention of you trip from the Continent but congrats you got it together and so far *good3*
Do not use springs wound the wrong way on a 3 or 4 spring clutch because hey will allow the adjuster screw to unwind.
On an older clutch where you can fit lock nuts it dosn't mater but on the clutches with the mushroom shaped sleeve nuts they are a disaster.
-
Hey Dutch- you are disputing what I say and you're quite right. It looks impossible for the pressure plate to foul the centre, in that clutch.
Are they all as deeply dished as that?
I'm pretty sure mine is not so far below the cage.
-
.......- you are disputing what I say and you're quite right. ........
...just usin' my best diplomacy *smile*
Do the spring cups ever bottom out on these things?
Good question, one that I've been meaning to investigate for some time- NOW is that time.....
So here's some pics that show;
#1> the inside of the Pressure Plate, and in the first two pics have inverted the Spring-Cups at the absolute possible (bottomed out), which shows in;
#2> the bottom of the Cups just level with the Pressure-Plate sitting accordingly Bottomed-out.
#3> Third pic is the Cups in normal position,
So my conclusion is; If the Cups were Bottomed out would be sitting a bit proud of the Pressure-Plate.
- obvious to see there's not much in it though *eek*
Edit; just measured the cups @ ~1.231"/31.25mm (underside of lip to bottom of cup) Cup-surface of Pressure-Plate to inside-Bottom of Clutch Inner = ~1.273/32.33mm , so There's about 0.040" (40 thou/1.0mm) clearance- not much to play with.
That's on my spare anyway, others may be different *conf*, I'll measure my unit in use next time I have it off.....
I'm pretty sure mine is not so far below the cage.
Shirley GB, if you took all the plates out it would *smile*
Do not use springs wound the wrong way on a 3 or 4 spring clutch because hey will allow the adjuster screw to unwind.
On an older clutch where you can fit lock nuts it dosn't mater but on the clutches with the mushroom shaped sleeve nuts they are a disaster.
I totally agree Trev, that's why I've never used 'em. I asked for opinion about this ages ago, but don't recall any feedback (until now *good3*)
-
The other obvious possible outcome of the above conclusion is out may be possible that tube chips have been replaced with longer incorrect ones... *dunno*
-
Hi Dutch,
How many plates in that clutch?
It looks like is short a few as the upturned cups are virtually level with the pressure plate??
I know that the centre will not be sitting against the chainwheel when on the bike
Take a pic of the plates stacked onto the inner drum, with the pressure plate and upturned spring cups
John
-
John, there's no plates in it.
The pics are purely for demonstration to show the absolute extremity of pressure plate travel, (which won't happen with plates in ) , in answer to TT's question and to satisfy my own curiosity and also provide a possible answer to Owains dilemma... *smile*
-
Well, I've cleaned all the plates (friction and plain) in petrol and used 400 grit wet sand paper on a piece of glass. Also placed 2 washers into each of the clutch spring sleeves. Didn't make any difference.
I'm pretty tired of disassembling and reassembling the entire transmission everytime I made a small alteration. So I left the transmission case and clutch cover off and had a look at the transmission when it's running...The clutch is working fine....What is not working very well is the shock absorber, with heavy load (given some throttle) the spring immediately compresses and transmission is lost. When I placed the shock absorber spring onto the crank spindle during the rebuilding of the engine, it went on very easily. I had to really struggle to compress the spring and get the nut onto my B33 but this spring went on with no squeezing needed at all. Surely this indicates that the spring is well passed it's due date?
-
Hi Owain,
WTF *????* *????* *????*
Its a wonder that the crank or something has not broken????
If the crankshaft nut is fully tightened, which it should be *ex* tightened to 65ft/lbs
The cush drive assembly should not be able to "slip" even if there was no spring there
If the bike has been run with the nut not tightened fully any shims that are fitted to set the crank end float
can and will break up *sad2*
John
-
G'day owain.
Something very amiss in there. The spring is either shot or the wrong one. There are 3 springs listed for our A's. 67-2052 = long stroke A7's,
67-2062 = plungers 50-57 and s/a 54, 67-1136 = s/a 55-62. I can't say the correct lengths but someone will.
Cheers
-
If the cush drive cams were jumping over each other, that should have been noisy.
-
I busted a spring a couple of years ago, and was still able to ride around for a while with no dramas until I got around to having a bo-peep...
I think it was making a bit of a clunk when I rolled it over with the kicker, but nothing much else untoward.....so having said that, I know the cams will still still engage without any spring at all, but can't remember if it still engages with a loose nut.
Even though I ordered a new spring of the correct number, I think I was sent the wrong one (for S/A), or it's just crap- shorter and a bigger diameter , so it doesn't sit on the sliding /fixed sleeves comfortably (in fact I used a short length of SS exhaust pipe to sleeve over the sliding bush and nut, these sleeves don't spin or slide- just 'space'), so I now have some lash and a clunk at times when engaging kicker, and or in and out of the 'dead-spot' between power-on/power-off- otherwise it rides around without drama- (except the previous mentioned minor slippage), but WILL change it when I find a better one(note to self).
I did a rant about it at the time- a search might find it, I'll try that later if need be.....but I don't think that's the problem of the clutch breaking loose; maybe owain you just over-charged the engine when you re-built it *smile*
-
I ordered a new spring from Draganfly (67-2062). It hasn't been making much of a noise tbh. It was only when I drove the bike around without the transmission cover on that I noticed it and only visually as well. Either way this spring seems well off, I have a feeling that I may accidentally placed the A10 shock absorber spring into my Triumph unit engine as I was rebuilding both engines simultaneously and in a messy workshop :S
-
........, I have a feeling that I may accidentally placed the A10 shock absorber spring into my Triumph unit engine......
I've only owned one of them, and it was a T100R (Daytona) but I didn't think the Unit models had a cush-drive that you coud mix it...*dunno*
-
Ah you're right dutch. I guess it's just a spent spring then...or just a bad mechanic ;)
-
Righto, new engine shock spring arrived today. No difference in height with the old spring. The cush drive cam is still sliding over the on the sprocket. Starting the bike is now an issue as a forceful kick causes the cush drive cam to disengage immediately. The only thing I can think of now is that the cush drive cam and sprocket (type with 2 lobes on it) are badly worn. It does look visibly worn on inspection with heat marks at the top of each lobe and with one side of each lobe uni-laterally different in profile. Being a cheap bugger, I tried using a dremel to exaggerate the profile of the lobes on both the sprocket and cush drive cam, hoping that it would make it harder for them to slide past each other...no luck.
Is this a common problem with 2 lobe cush drives? Is there anywhere that I can get a new cush drive/sprocket and do you think this could be the solution?
-
Try Andrew at Priory Magneto's. I may have this wrong but aren't you currently in the UK?
-
Can you post photo of your assembly?
-
Can you post photo of your assembly?
Good idea. Sounds like a mis-match of parts.
-
It won't seem to post any images on this thread :S. I recorded this video though, if that helps.
https://www.youtube.com/watch?v=-TvrxRBItd4
-
The spring does not look like it is being compressed enough.
Is the cush nut fully tightened against the sleeve?
-
Yeah, I can confirm that the cush nut is fully tightened and pressing against the sleeve. And Yes Graybeard, I'm currently in the UK :)
-
The spring does not look like it is being compressed enough.
Is the cush nut fully tightened against the sleeve?
I agree. On my machine there is a definite gap between the split pin and the nut.
-
I can't get the nut on any tighter, there is about a 1-2mm gap between the pinbolt and cush nut. Perhaps grinding a few mm off the nut? *conf*
-
I cured my Cush drive riding over by grinding the splined sleeve down until the spring became coil bound so it would not ride over its self . As said many times before you cant be certain that all the parts on your bike may not be correct. *smiley4*
ELLIS
-
The lobes on the engine sprocket look completely gubbed. If you can't get hold of a replacement, I most likely have one in my box of bits.
-
I clicked through frame-by-frame, and something doesn't look right (at 0:09 it shows a gap between the spring and the sleeve much like mine, so i reckon it's not the proper diameter spring which affects the tension); Even with no spring installed, the nut should stop the sleeve from sliding further so the cam lobes should engage enough to drive (well mine does), and not pass over (not reccommended, but if yours doesn't engage, then I guess that's a substitute for a slipping clutch *conf*). Plunger and Swing arm components are physically different, and the *sliding* splines are different sizes and are not compatible, so can't mix them. Plunger model Spring-nuts are stepped so the sliding sleeve can pass over it (trying visualize that in my own mind now).
If the spring Nut is fully tight, it *looks* in the right spot, assuming it's the proper one-hard to tell I think....perplexing, but we'll get it sorted; *dunno*
*beer*
-
Hi Owain,
As far as I can see on the video, you have mismatched parts
The cam and sprocket should be a close fitting match without a gap between them
so no relative movement without the spring compressing
As said before the assembly should not be able to ride over when the nut is tight even without the spring
John
-
I forgot to read Page 4 (this one) before I did my previous post, but just dug out my spare cush bits, and it appears that your sliding sleeve may have been shortened by at least 1/8" *eek* .
As can be seen in my pic the sliding sleeve hangs over the inner by ~ 0.028". You may be able to remedy (bodge) this with a packer shim on the minor diameter of the nut, but holding it in place (?- maybe with a light spring or squishy meal sleeve or similar) something to think about for a while *conf*
-
I agree dutch, Just as I said in my post. *work*
ELLIS
-
but holding it in place (?- maybe with a light spring or squishy meal sleeve or similar)
...
... or silicon face to face
I agree dutch, Just as I said in my post. *work*
ELLIS
Sorry, I might have not interpreted that properly, but I think I intended (but forgot ) to disagree with grinding any more, as I generally prefer to regenerate if possible, and was also distracted with other ideas *smile*
-
Actually Ellis - (not to be confused with Ashley- or Shirley *smile*), I'm still not sure which bit you ground, but I also don't like the idea of 'coilbound'....tholly *smile*
-
I think the parts dont match together. It looks like a 4 loop sprocket connekted with a two loop part.
cheers Klaus
-
Yeah Klaus, I reckon you're right *conf*.... my cross-eyes over looked that, would'na thought it possible but fairly obvious now I look harder *bash* , but probably easier to find a two lobe one than a four lobe(?)
-
Righto, I've done the bodge fix for the disengaging cush drive and stuck big washer between the the end of the sprocket sleeve and the cush drive nut. My only concern is that, should the cush drive nut come loose (used loc-tite and pin bolt to keep it in place) then the washer could potentially knacker the thread on the crank....should the drive nut come loose.... :o
-
Yeah, I can confirm that the cush nut is fully tightened and pressing against the sleeve. And Yes Graybeard, I'm currently in the UK :)
Your cush drive is wrong.
You have a 4 lobe inner with a 2 lobe outer and that is a receipe for disaster.
What has been happening is the lobes have been passing over each other.
You can go either way, although the 2 lobe is a lot stronger than the 4 lobe.
They also use different springs.
The 4 lobe uses a square section spring and the 2 lobe uses a round section spring.
The square section spring comes in a dozen different lengths so finding the correct one is always a bit hit & miss.
-
When I took everything apart, there were only 2 lobes on the sprocket and 2 lobes on the cush drive. There definitely weren't 4 lobes on either. Perhaps it may appear that way because I tried grinding the profile of the lobes with a dremel in a bid to stop them sliding over each other. :/
-
It looks very wrong to me an also looks like they are jumping over each other.
-
I totally agree , there is something completely wrong with that cush drive unit and I feel you may be stuck in Llandudno for some time if you don't change 'em . Is there any one on the forum in England who may have so spare bits of a plunger cush drive for you ? I can't see any other way to deal with it except change it !
-
Owain, you are about 80 miles from Andrew Guttman at Priory Magnetos who is very likely to have what you need.
-
When I took everything apart, there were only 2 lobes on the sprocket and 2 lobes on the cush drive. There definitely weren't 4 lobes on either. Perhaps it may appear that way because I tried grinding the profile of the lobes with a dremel in a bid to stop them sliding over each other. :/
Well now I have read you post properly, it confirms things.
The lobes should not be able to pass over each other with the cush nut done up to the shoulder.
You can check this without the spring.
If they can skip over each other then they either are not a set or are worn beyond their useable limits.
-
Thanks for all the help on this issue. I ordered a new old stock sprocket/cush drive sleeve/ such drive cam/ etc. When comparing parts it was very obvious why cush drive and sprocket lobed were sliding past each other...The back of the sprocket and cush drive sleeve were incredibly badly worn...in fact it had even won abit of the crankhousing behind the sprocket as well. (New parts on left/ Old parts on right).
-
That's the ticket owain now you will soon be up and running with no slippage. *smiley4*
ELLIS
-
Given the step in the flange part, I don't think it's worn like that, otherwise you'd also have a step in the worn part- I would suspect the sprocket part has been machined to accommodate some clutch mis-alignment which you'll need to address as you re-assemble (though I can't imagine how that would happen to such a degree, but still worth addressing).. good luck with it, you're lucky to find the parts and I think the sleeve part may be from a '54 on as the flange seems a bit wider than the other (not stepped), to accommodate a seal- but should still fit