Cush drive elimination

[Bsalloyd]

I have been changing all my old bikes to the four spring style clutches. The question is with the four spring clutch can the cush drive assembly be discarded? Of course I will keep the sprocket. Duh

[muskrat]

G'day Lloyd.
It depends on which 4 spring you use, with or without the cush type hub.
When I first started racing the A7SS I had a non cush 4 spring and left the cush drive on. With a strobe light to do the timing I was able to watch the cush work. I was surprised at how much work it did.
Basically the cush drive takes the shock out of the power pulses. Without it the shock is transferred down the line, chain, clutch, g/box.
No cush on the Cafe with belt primary, Notrun Comical clutch.
Cheers

[BagONails]

That's interesting Musky, I'm wondering roughly how much movement you could see, were you looking at the radial movement on the lobes or the axial movement against the spring with the strobe?

I'm still running my cush drive but due to the odd mix of components I ended up with roughly 40% reduced cush travel axially against the spring.  I didn't mind as this left me enough threads on the crankshaft to turn my old nut into an additional lock nut (turned down it fits inside the new one and tightens with a pin spanner) and dispense with the useless split pin.

No problems to report so far, I've done probably 2000 miles since the rebuild and I've only adjusted the primary and final drive chains once just recently. (All new chains and sprockets throughout).

[Black Sheep]

My B31 has a cush drive 4 spring clutch plus the original engine sprocket cush drive. Makes for wonderfully smooth transmission and gives the rear chain a very easy life.

[mikeb]

My B31 has a cush drive 4 spring clutch plus the original engine sprocket cush drive

i'd read somewhere not to have both - not sure why. I've just put a 4 spring clutch and cush centre on my plunger B and so removed the cush spring and made a spacer to hold the lobes together.
So Lloyd you can swap out the 4-spring clutch centre for a cush verison (a straight swap) but it creates other problems and... why?
(I have plans and reasons, just  probably not very good ones)

[muskrat]

G'day BON.
I witnessed the axial movement of only two to three mm, mostly at low revs. The higher the revs the less movement. Mind you I'm sure it was the original 1957 cush spring.
Next time I check the timing on the plunger I'll try to take a video.

Cheers

[BagONails]

G'day BON.
I witnessed the axial movement of only two to three mm, mostly at low revs. The higher the revs the less movement. Mind you I'm sure it was the original 1957 cush spring.
Next time I check the timing on the plunger I'll try to take a video.

Cheers

G'day Musky! That makes sense when you think about it. To really see what's happening you need a strobe that you can adjust the frequency on.
However, unlike you I don't thrash mine so I'm not overly concerned!

No cush with a belt drive either. Those belts don't stretch so there's not really any cush built in I wouldn't have thought. Is a cush drive detrimental to a belt and pulley system?  Or maybe the belt is tough enough to not need one then again the gearbox is still feeling the sting so I'm not sure what the ideal set up for long life and happiness really is...

[orabanda]

If the primary drive cush spring nut is torqued up (65 ft lb?) then the inner shoulder of the nut should be bearing against the shoulder of the crankshaft.
When a timing disc is bolted to the nut, it is isolated from the movement of the sprocket due to the cush drive working, because the outer nut & the crankshaft are locked together.

If the nut was not hard against the crankshaft shoulder, then a split pin would be required to stop the nut eventually coming loose.

Richard

[BagONails]

If the primary drive cush spring nut is torqued up (65 ft lb?) then the inner shoulder of the nut should be bearing against the shoulder of the crankshaft.
When a timing disc is bolted to the nut, it is isolated from the movement of the sprocket due to the cush drive working, because the outer nut & the crankshaft are locked together.

If the nut was not hard against the crankshaft shoulder, then a split pin would be required to stop the nut eventually coming loose.

Richard

 

Yes, as Richard has said it is most important that the nut is retained as it tightens against the cush sleeve bearing which in turn bears against the spacer, inner race of the drive side main roller and as such keeps all those nasty little end float adjusting shims in compression against the crank web shoulder.  Without this then all hell would most probably break out in very short order.

If the cush assembly is to be removed then provision must at least be made to ensure that the nut can still apply the all important clamping pressure as described above. Then you would also need a spacer in the mix to keep the engine sprocket running true, Probably easier to run with both original engine cush and clutch cush or keep the engine one and dispense with the one in the clutch ultimately maybe?

[chaterlea25]

Hi All,
I ran with both cush drives fitted for years,
No issues , I fitted a NOSsolid clutch centre when I fitted the electric starter, loses a pound or 2?
I could always get a bit of clutch slip about 4-5k revs until I fitted the 7 plate conversion and solid centre ... it's like a modern bike now!! Click click into neutral or first with the radial needle bearing  pressure plate there's no problem at traffic lights or filtering either..
I have posted pics before of how much an engine pulley wore on a Goldie after about 6k miles when no cush drive fitted
I got SRM to fit a pulley to an original cush sprocket for my RGS project, that's a while away yet

John