Hi Doug The pre unit triumph 4 spring clutch is the popular mod. It requires a adapter. BSA actually used this stock from 1960 on wards. I have always thought the 3 spring clutch on A65s or unit triumphs, but they have duplex chains? So if it fits OK on the output shaft of the gearbox. The chain alignment is good I'd give it a try. Jeff
Re: Bsa 3 Spring Clutch A10?#6755 12/25/057:02 pm12/25/057:02 pm
Hello, Well I put the triumph three spring clutch and the a10 on the work bench and found the parts are interchangable. They seem to fit and with the later three sprng you get two more plates. I just have to work out this copper thrust washer that I see in an A65 clutch blowout. If this will fit in behind the chainwheel it might solve the slop normally found in the stock A10 setup.
Re: Bsa 3 Spring Clutch A10?#6756 12/25/0510:40 pm12/25/0510:40 pm
Here's my spiel I've posted before on the pre unit BSA clutch issue.
The 'common as dirt' pre-unit 'Tri type' 4 spring clutch has been used succesfully by myself and thousands of other riders over the years. And nearly all of us are now using the readily available repop parts. Luckily we Beezer guys no longer need to fight/fuss/curse/hate those olde/early 6 spring POS BSA clutches!!
I have a bit of experience with the 4 spring clutch and perhaps some of these general issues I'll mention may apply to your situ. I dunno. Sadly, I've learned some of this "the hard way", mostly experimenting both myself and also learning from the experiences of others, mainly GStarRon who I consider a 'guru' on this subject. We are always trying to reinvent "the better mousetrap". "Win some, loose some", aarrgh.
For starters ... The design of the older 4 spring pre-unit clutch is bit different than the later 3 spring clutches, even tho they appear to operate the same. Follow along here .. I've noticed this area is Not common knowledge.
The pre unit 4 spring 'clutch center' has small shoulders at the ends of the grooves the driven steel plates engage. These 'stops' prevent the innermost steel plate from bearing against the inner face of the chain wheel at any time, even when the clutch is engaged. This is why the first plate installed into a pre-unit chain wheel is a steel plate.
When this clutch is disengaged, the pressure plate is pushed out and the spring pressure holding the plates together is released like all clutches. BUT when the bar lever is released and the springs push the plates together the 'clutch pack' and spring pressure bears against the innermost steel plate supported by those shoulders at the ends of the grooves of the chain wheel.
This is why the pre-unit 4 spring chain wheel has a bit of 'wobble' side to side even when the clutch is engaged. It is located merely by the end play in the roller bearing assembly. BTW, this sucks and I consider it a big design flaw. Comprende?
The later and better designed 'unit' '3 spring' clutches work a bit different as I've mentioned. There are No shoulders at the base of the grooves of the clutch center the steel driven plates bear against. A bonded face driven plate is the first plate installed into a unit clutch as it bears against the inner face of the chain wheel. If you notice the clutch adaptor on the mainshaft has a nice wide thrust face with a largish bronze thrust washer. This thrust face bears against the the back side of the chainwheel at all times.
When the unit clutch is disengaged the lubed thrust face on the adapter is pressed against the back side of the chain wheel by the pressure of the clutch springs unlike the pre unit clutch which carries the pressure against the inner most steel plate. OK?
When the unit clutch is engaged, the 'clutch pack' Includes the chain wheel and everything is locked up in a nice lump. Because of this the chain wheel is locked up on the tranny mainshaft and doesn't wobble. This is "A Good Thing".
There are a couple/several different lengths of clutch springs and cups used over the years in different bike models. Be sure to use the correct spring and cup combo. What you grab off a 'swap meat' table may not be 'the right stuff'.
The BSA & Tri chain wheel bearing rollers are a bit unique. They are not the common 0.250" x 0.250" size roller easily available. But instead are 0.235" long which allow end play in the bearing. If the common bearing house supplied 0.250" long rollers are used all the end play will be lost and the clutch center will jam/lock the rollers up against the the flange of the adaptor when the mainshaft nut is tightened. Make sense? I learned this the hard way one night trying to finnish assembling a racer clutch at 2:00 AM! aarrgh.
Not all early 4 spring chain wheels are made the same. Some (all?) of the OEM chain wheels had a "dished", back face. In other words the sprocket was not made on the same plane as the back side of the wheel, but was inset approx a 100 thou towards the tranny. Because of this when installing a repop chain wheel with a 'flat' back face, the chain alignment will sometimes require you to use a thick shim behind the engine sprocket to align the engine and clutch sprockets. I sure hope everyone is checking chain alignment!
This is easily and quickly done. Before the inner primary cover is installed, merely snug fit up the engine sprocket and clutch chain wheel. Using a straight edge on the back side of the sprockets, insure they are in alighnment. If not adjust the engine sprocket position with shims on the crank shaft.
I and others have discussed this alignment issue at length. Strangely, it's not an issue with some bikes. Perhaps some mainsahfts are also different lengths? hmmm
Watching your pressure plate, does it smoothly move in/out when the lever is pulled? Are your springs adjusted equal so the plate spins 'flat' and the clutch is free when the lever is pulled in and the kicker is pushed through? Do you have difficulty shifting gears due to a dragging clutch?
Another story: With my 20k+ high mileage much abused 4 spring clutch on my Goldie, I was noticing increasing chain wheel "wobble". Yup things were wearing out. When a "Triumph type", 4 spring is installed on a BSA, a different clutch adaptor p/n 42-3170 is used to match with the BSA tranny main shaft. BTW, this is the part and set up as was OEM BSA on '62 and '63 GSs and A10s. Anyhow, the chain wheel had "wobbled", long enough in service so as to cause the narrow flange of the adaptor to wear into the back side of the chain wheel and was even pushing the bearing race out of place slightly into the chain wheel face. Remember, this flange is not a "thrust face", with a 4 spring clutch but merely 'locates' the chain wheel. So... As we were using Tony Hayward belt drive clutches adapted to BSA trannys on other GSs, Ron and I had a bright idea that worked great. The Hayward clutch uses some BSA & Tri unit 3 spring parts. But the unique clutch adaptor sold by Hayward has a large thrust face just like a 'unit' BSA/Tri adapter, but the bore and taper fit the pre-unit tranny mainshaft. hmmm. So I merely used a Hayward belt drive clutch adapter with the large thrust face on my 4 spring chain wheel. No more excessive chain wheel wobble. woof.
From now on I will always use a Hayward adaptor with a 4 spring clutch build up on a Goldie vs the OEM design. And I believe with this piece I'm sure you could also adapt later 3 spring clutches to the early bikes. hmmm? ...
"Too soon old, too late smart". dave - NV with a high mileage and much abused 4 spring clutch on a kinda fast Goldie with Barnett plates and 10-30 oil in the primary, that pulls in softly with 1 or 2 fingers, squeaks the tire and has tolerable drag.
dave - NV
Re: Bsa 3 Spring Clutch A10?#6757 12/25/0510:51 pm12/25/0510:51 pm
The Triumph-type clutch must have come on at least one of the pre-unit models because I got a hold of one of those clutch conversions years ago myself.
The key to the whole thing is the "hub". If you've got the hub then you can build a 3 or 4-spring clutch that is far superior to the original BSA item.
Triumph basically used the 4-spring on the pre-units and the 3-spring on the units, but since the only difference is the central "cush" housing it makes little difference. I prefer the 3-spring myself due to the larger cushions, ease of truing and ready access to spares (Triumph used that design until the end). The same hub and roller combo will support multi-row chain wheels or single row.
That's an item you won't want to trade or sell. Congrats on a great find.
Don't hide 'em, Ride 'em !!
RF Whatley Cornelia, GA
"Shop Boy" at Rodi British Bikes
Re: Bsa 3 Spring Clutch A10?#6758 12/26/0512:06 am12/26/0512:06 am
Thats the wonderful thing about this board. Someone like Rocketman asks the leading question and all of us lurkers benefit big time from the responses. Myself in this case being the owner an A7 and A10 - both with the dreaded 6 spring clutches.
Thanks very much Dave for the excellent treatise (as always). You have a knack for making complicated issues understandable with your masterfull way with words as I'm sure many have told you. As does Redneck :p as well for that matter.
Really greatfull to you two gurus as well as John Healy, Panic and Tom Sharp (and others) who take the time to provide us with the benefit of their experience and expertise.
P.S. Hope that you are having a nice Xmas. And, BTW hope that Joel is fully recovered and raring to go again
Re: Bsa 3 Spring Clutch A10?#6759 12/26/051:01 pm12/26/051:01 pm
Good explaination Dave. It appears that the length of the rollers would be the main issue on mounting the 3 spring unit clutch hub. I have been around the A10 for many years but never understood why there was no thrust washer behind the chainwheel. Yes, the clutch always seemed to make gear changing snatchy. I agree on the design flaw.
What I am shooting for is: A10 clutch center pre-unit 1960-1963 Triunph\BSA unit type 3 spring hub Standard A10 rollers (Thrust washer mounted behind the chainwheel against the clutch center (what would be minimum thickness?)
Clearance between rollers and clutch hub should be ???
Does this sound reasonable to remove the wobble or should I go for the Hayward adapter? Where is this adapter avaiable?
Thanks. It's getting there. Doug
Re: Bsa 3 Spring Clutch A10?#6760 12/26/052:26 pm12/26/052:26 pm
Good thread for me to try and soak up too, for current -in process- '56 rebuild. Have heard people say they used a 3 spring clutch center, but couldn't quite understand what keeps the first plate in from falling off the back, since the 4 spring clutch center has the little shoulders. Now I think I get it.......simply put a fibre or bonded plate in first and there won't be room for the next steel plate to fall behind the clutch center and the back of the basket, when the clutch is released. I still need to buy a Tony Hayward hub adapter and thrustwasher...
Unity Equipe has them I believe anyone else carry them in North America I wonder???????????
Already have new correct length rollers and again..Glad the experieced have pointed out these critical details for proper function. I think it's already been discussed about the "double cush" when using a unit 3-sping center or early 4 spring cushed center (like mine) and I have been told "you won't notice it" and "don't do it" ....referring of course to removing the spring from the front cush assembly. I'm gonna try the double effect myself and see just how spongy it may or may not make the action. But as of now ...planning on a "just happened to be laying around " 3-spring unit center (with more plate capacity...gotta be good right?) in a new pre-unit basket. (I'll be checking the primary chain alignment too) Good stuff you guys are talking about here!
GOLD S-TARvin OVBSAOC # 1625 1960 DBD34 Gold Star 1956 DB34 Gold Star 1969 Bonneville several basket case Triumphs
Re: Bsa 3 Spring Clutch A10?#6761 12/26/055:32 pm12/26/055:32 pm
All - The 3-spring clutch I mentioned having was used on a DBD34 along with the crankshaft mounted spring cush. It ran great. Your gearbox and neck vertebrae will love it.
BTW, I understand that when you use the Triumph clutch that you must use the Triumph rollers as well. The BSA rollers look the same but are (apparently) about .015" longer and lock-up the clutch when the mainshaft nut is tightened up. My boss ran into that issue recently.
Clutch basket wobble or looseness on a Triumph clutch assy doesn't mean a dang thing. When the pressure plate and pressure springs are installed, the entire basket, et al, is pressed back against the clutch hub and all looseness and wobble go away. Wobble only returns when the clutch is disengaged, which is about a total of 3 seconds for every 100 miles. So of all the things to keep you awake at night, this is NOT one of them.
Don't hide 'em, Ride 'em !!
RF Whatley Cornelia, GA
"Shop Boy" at Rodi British Bikes
Re: Bsa 3 Spring Clutch A10?#6762 12/27/059:12 am12/27/059:12 am
Howdy RF ... uhhh gee, you've made a couple of comments I don't agree with ..
I believe you'll find ALL BSA clutch rollers used in either the pre unit 4 spring or the unit 3 spring clutch are the same dims .250" dia and .235" long, the same as the Triumph parts. But ... the commonly available (cheap) 'bearing house' .250" dia rollers are .250" long. These longer rollers will lock up the clutch as you describe.
And ... Clutch basket wobble on the Pre Unit 4 spring BSA or Triumph clutch is always the same whether the clutch is engaged or not. Sadly going down the road the chain wheel wobbles all the time .. and wobbles more and more as time goes on and parts wear. And yup, it used to keep me awake at night worrying. heh.
But .. the later model Unit ie: 3 spring clutch chain wheel Only wobbles when the clutch is disengaged. I'm quite sure this is the type clutch you are familiar with and referring to. Going down the road the clutch chain wheel is locked up in a lump on to the tranny main shaft. "This is a good thing". If you are interested in 'why' reread my previous description of the differences between the two clutch designs.
dave - NV
Re: Bsa 3 Spring Clutch A10?#6763 12/29/052:17 pm12/29/052:17 pm
Hi Guys Well I am learning lots here. So a couple of questions. 1. How is the best way to get a hold of Tony Hayward. Does hwe have email or a website? 2. The 3 spring clutch: what is it from? What type of chain wheel does it have, is it a single or double row chain. Lastly does any one have any experience putting one on a plunger A7? Heres another thought. This Suzuki clutch conversion that people are using in the UK is it posible to find out what model used it and get the bits from a scrap yard? Jeff
Re: Bsa 3 Spring Clutch A10?#6764 12/29/054:27 pm12/29/054:27 pm