The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: chicago on 06.06. 2013 14:45

Title: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: chicago on 06.06. 2013 14:45
Hi fella's, been getting vibration (not massive) and knocking noises from the primary case side of bike, thought at first big ends, bought a mechanics stephoscope and traced the knocking noise to the clutch basket area, no knocking at all from the crank area. took the primary case off and play in the basket again (heres a video)
http://youtu.be/fFe91tvO7Zc
I had the same problem last year and replaced the roller bearings which made it a bit better but not perfect, I'm now thinking of converting to a 4 spring clutch with single chain or possibly a belt drive, my question is this, would a 4 spring clutch of a later short stroke/swing arm a10-a7 fit or would I have to get one that's designed for a Longstroke, I've got about £380 quid and spotted these on ebay.... http://www.ebay.co.uk/itm/321131323073;jsessionid=B03794CDC4C97AE3B3135DE98247991E?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D321131323073%26_rdc%3D1
and http://www.ebay.co.uk/itm/151053684413?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D151053684413%26_rdc%3D1
would either of these work ?. Cheers in advance, Chicago
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: muskrat on 06.06. 2013 15:10
 Neither will fit chicago. The s/a has a taper mainshaft, your plunger has a spline. The cush can be swapped for a s/a type.
I haven't done it but I believe a Norton clutch will fit, don't know which model.
Cheers
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: chicago on 06.06. 2013 15:59
Cheers muskrat, looks like I might be stuck then. Pitty I couldn't make one of these roller bearing washers fit behind my basket as that would stop the play
http://www.ebay.co.uk/itm/221124114323?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D221124114323%26_rdc%3D1
The centre of the clutch is rock solid, it's just the basket. Is there no fix possible for this without having to replace the basket ?.
I take it that it wouldn't be possible to undo the mounting bolts on the gear box and pull the gearbox towards the timing gear side of the bike to reduce the play ?.
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: muskrat on 06.06. 2013 21:04
 The three parts that wear are the clutch chainwheel inner bearing surface, the rollers and the thrust washer. I don't know if you can still get them but the thrust washer came in 3 sizes (thickness) .112-.126", .138-.140", .148-.150". I have never replaced mine so I can't say how the different sizes act.
 Moving the box (if possible) won't help.
I think I remember someone here replaced the rollers with a bearing. Do a search.
Does the knock go away when the clutch is dissengaged ?
Cheers
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: chicago on 06.06. 2013 22:57
Cheers muskrat, thrust washer and new roller bearings might be the way to go then. The knock seems to go better when you pull the clutch in. I've got a video of the bike running with the primary cover off and me pulling the clutch in and out but very hard to tell the difference on video but stood next to it you can tell. Here's the video anyhow....
http://youtu.be/DqwI_Rn_rCg
Cheers fella
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: gold33 on 07.06. 2013 04:53
The three different thrust washer sizes pop up regularly on fleabay.
I am in the process of having my chain wheel refurbished ie. new outer bearing surface machined and pressed into place. I had no trouble with my clutch until it fell off (once everything was adjusted) so I'm hoping the same applies when it is re-assembled, my only concern is the fact that it previously had less rollers than it is meant to. If this fails I will be going down the bearing conversion road.
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: Topdad on 07.06. 2013 11:19
Good morning Chicago, just moving back abit re Muskrat's mention of a Norton clutch fitting .This stired a braincell and I remember that this info was mentioned in an article in "the classis m/cycle" by R rossendalen the tech guy there . In the past I've phone d the mag on anther matter and he's returned my call later and was very helpful .Otherwise Tony Hayward  01244 830776  ,who does belt drives in north wales / flint is very helpful and can convert to norton clutches whilst doing belt drive conversions  so he may have alternative ideas for you to consider , I'd give him a call regards BobH
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: A10Boy on 07.06. 2013 11:28
Chicago
As has been mentioned you can fit the better AMC clutch to your bike. In fact, some people have fitted splined plunger mainshafts to their swing arm gearboxes for that very reason. I haven't done this myself, so you will have to research which clutch to use, but I believe it is the one used on AJS Models, 20, 30, 31, Matchless G11, G12, G15 and Norton Dommies. All are readily available, you can contact AMC spares or the AJS and Matchless owners club for more details.

The BSA 6 spring clutch has a well deserved repuation for being total rubbish in comparison.
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: Topdad on 07.06. 2013 12:26
Bingo , thanks A10boy  , the article was a complete study rebuild  about  rrt2 boxes and during the article it showed all the various mainshafts ,plunger std ,s/wing arm and RRT the expert doing the work stated that a very popular fix was fitting a plunger mainshaft and Norton (read Amc ) clutch as you just confirmed.
I concur totally about bsa 6 spring clutches .

And nice to hear that AMC  ( and I do just mean Amc not the original marques when they produced there own bikes ) actually made something that worked  *whistle* regards BobH.
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: duTch on 07.06. 2013 16:30


 Chicagogo, Even though my clutch is currently working fine, I do have the similar slip/slop/slap that sounds as yours, and also maybe some eccentricity, but can't offer any more remedies than already offered.
 I have/had a Norton diaphragm basket, and the splines are same, they are a triplex (maybe not such a prob), but have a larger diameter(more teeth) and don't fit in the case, but I've taken note of the suggestions also, but keeping in mind the plungers are I think a smaller diameter than the S/A mods..??
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: muskrat on 07.06. 2013 21:12
 In my opinion our duplex 6 spring plunger clutches are far better than the later swing arm type. Look at clutch problems posted on this forum, I'd say 90% are the s/a 6 spring.
 I replaced the friction plates, rollers, springs and chain over 30 years ago, the rest is original '51. Haven't had a problem since.
Cheers
Title: Re: Clutch conversion, plunger six spring to 4 spring, maybe belt drive ?.
Post by: chicago on 08.06. 2013 00:59
Hi cheers for covering all the options for me fella's, been having another look at the basket and the teeth on the chain sprocket are quite badly worn as well, Infact to the point that the crown of the teeth are starting to chip off, so maybe not worth having it machined or having a sealed bearing conversion, pitty as would have prob been the second cheapest option ?. I think ill try and get a new thrust washer and some new rollers to make do for the next couple of months, I'll give tony a call to see how much for a belt drive conversion, hope I don't need a chair to sit down when I get the price   *cry*, once again fella's a big thank you for taking the time to answer.