Hi Folks.
I've recently overpaid for an M33 Bitsa, a 52 B33 in a 53 M21 frame. On removing the chaincase I was surprised to find a complete lack of cush drive, which has been entirely replaced with a spacer and a 19 tooth direct drive sprocket ?
With a 4 spring clutch conversion. Does anyone recognise this scenario ? Is it a hash up that requires returning to original ? It seems to run ok.
I did see a note on a forum somewhere that some 4 spring clutches have an integral cush drive ?
This is my first post here, and have tried posting a photo from my phone, but have yet to learn the method.
Best Regards Steve.
So after a bit more research it seems a similar setup to a B50 or B40 or possibly a 1958 B33 (last production year) that had a 4 spring clutch with an internal cush drive, with a fixed sprocket. So I've just to identify which mashup of parts have been applied.
It sounds as if you have a Triumph 4 spring clutch. This has rubber inserts in the clutch centre. The normal 4 spring for a BSA has no inserts and relies on the cush drive on the engine drive shaft. A 1952 engine would have a 4 lobe cush drive, although on my 1949 M33 I have changed to a 2 lobe as I think they give a better drive. If the system you have works without lots of snatching then leave it, it is now no worse than a Triumph. No one can see it either.
Thanks Idle.
That would seem the most likely scenario. It seems common to use the Triumph 4 spring clutch.
The unit singles had a double chain, by looks of the B50 Manual.
The AC b33 models for 58-60 did have a cush drive inthe clutch with a single chain it seems, but it seems the triumph version was the most common 4 spring conversion from what I can glean.
Just a bit disconcerting to spot a big chunk of engine part not there when the case came off.
So it seems fine for now, and I can get on new valves and guides, and finding somone to straighten the frame. As the wheels appear to have a devil may care attitude to alignment.
with that conversion you avoid the dreaded 6 spring clutch . so an upgrade . but those 4 spring clutch centres do wear out.
Apols *Idie*
Quote from: HackneySteve on 12 Dec, 2021, 19:18
Apols *Idie*
Thanks Eddie, what is the sign they are worn ? Do they run out of adjustment ? or slip ?
Given the Frankenstein nature of this bike, I doubt it was new when fitted. Although the sprocket teeth seem ok and the chain isn't has ok tension.
they knock when worn and can cause clutch drag. just pull the centre about and check for play to splines , vane or rubbers.
new ones from lpharris around £100 - not bad price.
Thanks Eddie.
If the rubbers in the clutch are worn you will notice a distinct knock when you accelerate and slow down.