The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => Gearbox, Clutch, Primary => Topic started by: Dean on 13.06. 2021 19:14

Title: Is there a conversion for plunger clutch
Post by: Dean on 13.06. 2021 19:14
Does anyone know iof there is an off the shelf conversion to the 4 spring clutch for the plunger 6 sping clutch?
Title: Re: Is there a conversion for plunger clutch
Post by: Greybeard on 13.06. 2021 23:24
I don't know the answer to your question but I do know that the 6 spring clutch used on the plunger bikes is superior to the swing-arm 6 spring clutch.
Title: Re: Is there a conversion for plunger clutch
Post by: Minto on 14.06. 2021 00:16
I don't know the answer to your question but I do know that the 6 spring clutch used on the plunger bikes is superior to the swing-arm 6 spring clutch.

Yes, apparently if set up well the plunger 6 spring clutch is very good indeed... I have yet to experience this. Mine after adjusting the drag and slip out of it and stopped the cover allowing all the primary drive oil in to soak the plates, still requires Popeye to operate it.
Jase
Title: Re: Is there a conversion for plunger clutch
Post by: KiwiGF on 14.06. 2021 00:25
Does anyone know iof there is an off the shelf conversion to the 4 spring clutch for the plunger 6 sping clutch?

I also do not know the answer to your question but have heard a norton commando clutch fits the splines of a plunger mainshaft, I have not tried this out but thought it worth mentioning in case you have some mates with notruns  *smile*

I am not sure which year commando, or if it is a diaphragm spring clutch.
Title: Re: Is there a conversion for plunger clutch
Post by: Joolstacho on 14.06. 2021 01:30
Wish I could help more, BUT yes, there is -or at least was an adaptor to fit the 4-spring clutch replacing the 6-spring one.
I did mine about 35 years ago but I can't remember where I got the adaptor sorry. I bought a lot of stuff from Armours at the time, maybe try them?
Title: Re: Is there a conversion for plunger clutch
Post by: Black Sheep on 14.06. 2021 06:45
The 6 spring plunger clutch is pretty good. If it's as heavy as a Norton Atlas there's something far wrong. Go back to basics - cable routing, cable lubrication/replacement, spring strengths, clutch plates. You know the drill.
Title: Re: Is there a conversion for plunger clutch
Post by: Greybeard on 14.06. 2021 09:45
... still requires Popeye to operate it.
My clutch slips if I give the bike too many beans, the clutch operation is easy-squeezy. I will take the cover off and tighten the springs when I can be arsed.
Title: Re: Is there a conversion for plunger clutch
Post by: Rex on 14.06. 2021 18:59
After a lot of plate tweaking etc the clutch on my plunger is pretty sweet now. Nice feel and little/no crunching into gear.
Not as good as the Ariel or Scott, but pretty good for a BSA... ;)
Title: Re: Is there a conversion for plunger clutch
Post by: a10gf on 14.06. 2021 20:24
On the plunger back in the days, after beeing sure all parts were in good shape (replacing whatever was needed) I spent quite some time fine tuning the springs for a completely even lift all around + finding out the right pressure slip vs easy to operate. ...& don't mind a dose of normal clutch assembly wooble.

At the end the old 6 spring system became perfect in every way. imo it's a good piece of engineering, just needs it's tlc. One of the absolutely best behaving parts on my bike.
Title: Re: Is there a conversion for plunger clutch
Post by: BSA_54A10 on 15.06. 2021 09:12
The spline on the mainshaft of the plunger box is the same as the Burman boxes used by just about everyone other than BSA & Triumph.
AFAIK just about any Burman clutch will fit on the shaft , after that it is just finding one that will fit inside your primary with the right number of teeth .
Never been able to have this confirmed but I have always though that BSA bought in those plunger boxes complete with clutch.
Particularly as the plunger B & M series use a std BSA clutch
Title: Re: Is there a conversion for plunger clutch
Post by: Greybeard on 15.06. 2021 09:45
Never been able to have this confirmed but I have always though that BSA bought in those plunger boxes complete with clutch.
Interesting. Who knows about the Ariel Huntmaster clutch?
Title: Re: Is there a conversion for plunger clutch
Post by: Rex on 15.06. 2021 10:23
I wouldn't hanker after a Burman clutch on a BSA. I have a Burman BAP box on a Panther, and they're renowned for having a poor lift mechanism giving less lift and plate separation than would be ideal. 
Getting a crunch-free shift into first at a standstill is next to impossible, and takes DTI accuracy on the pressure plate and a slow steam engine tickover to get anywhere near. The plunger clutch is far nicer to use.