The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Tone on 11.08. 2009 21:35

Title: clutch
Post by: Tone on 11.08. 2009 21:35
Hi All, I am reassembling the clutch on my swinging arm A10, it's got a triumph 4 spring non cush clutch. What I would like to know is, (without the plates in) when the centre nut is on tight how easy should the centre move? because I can move it by hand but it is quite tight,I put the lock washer on first, then the washer with the scooped out bit on the inside then the nut with the turned down bit inside so it goes through the washer, is this right? Cheers Tone.
Title: Re: clutch
Post by: LJ. on 11.08. 2009 21:45
The clutch centre should not move at all... It is on the mainshaft taper and should have a 'woodruff' key in the slot, the nut should be tight and tab locked over. In fact it should be difficult to take off and requiring a puller to remove it.
Title: Re: clutch
Post by: Tone on 11.08. 2009 21:55
Sorry LJ, I didn't explain it very well, it is tight on the shaft what I meant was you can twist the centre section (shaft included) whilst the chainwheel stays still.
Title: Re: clutch
Post by: RichardL on 11.08. 2009 22:52

If I understand you correctly, if you are in neutral, it should turn easily, rotating the unengaged shaft of the gearbox. Shift into gear and see how it feels. If you are on the center stand, and the chain is running to the rear wheel sprocket, the rear wheel should move with a bit of strong hand turning of the clutch center.

Title: Re: clutch
Post by: Joolstacho on 30.01. 2010 11:02
This might be a silly question but...
Any reason we couldn't run a 'dry' primary chaincase, using modern O-ring chain on the single row primary?
An occasional squirt with sticky chainlube, no oil needed, the clutch should get enough general 'haze' unless you're doing lots of city work.

(More silly questions to come)
Title: Re: clutch
Post by: bsa-bill on 30.01. 2010 11:38
a friend tried this with a standard chain, result was the chain got too hot, might work better with a modern chain but I would think you would still need some form of cooling like drilling your case or an air scoop somewhere.
Worth a try if you have a spare chaincase outer.

All the best - Bill
Title: Re: clutch
Post by: muskrat on 30.01. 2010 11:54
G'day Jools, the other problem would be the clutch bearing running dry. Unless modified with a modern sealed bearing.
Title: Re: clutch
Post by: 1660bob on 30.01. 2010 12:04
EEEK !-No,don`t run a primary chain dry-There is a fundamental difference here-it is spinning  MUCH MUCH faster than a rear chain and will quickly overheat (It already has to cope with a hot environment), as well as vital lube, the oil transfers the heat generated by the chain back into the casings and thus to atmosphere, a cooling function that your chain lube cannot do, and oil obviously will re-penetrate the roller links at every opportunity-again your chain lube cannot do this.Rear chains at best are in a hostile environment and "get by" due to their relatively low speed, they are a compromise of cost over engineering(theoretically all bikes should have a nice, enclosed shaft that road grit cannot get at-but again its cost.Thus to expose your primary chain so is a recipe for disaster IMHO.OK  yesteryear on Manx Nortons  for racing where they were replaced often/every race and fully exposed to aid cooling-even then (famously) snapping all too often!Bob.