classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: ramwing7 on August 24, 2026, 05:49:39 PM
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I have a couple of questions about the clutch on a 1949 BSA B#! rigid. It's a 6 spring clutch.
The clutch basket that came on the bike is worn beyond reasonable repair. I manage to fine a NOS one on evilbay, but when I started reassembly I notice a couple of differences.
1. The band around the clutch basket that came with the bike is 1 inch wide.
The "new" one is 1 1/4 inch.
It seems to clear the outer cover so no rubbing or dragging is noticed.
Is that difference in width going to be a problem?
2. My mechanics manual states that the clutch should have 5 fiber plates, although some folks went with 4 back in the day.
My bike came with 3
Should I add one or two or is it ok with the 3?
3. Last question. When I torque down the mainshaft clutch nut (no where near the 60 ft-lbs, but tight) the transmission seems to bind up It turns, but is tight.
I look forward to your advice.
Thanks.
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I wouldn't know a BSA clutch from a bar of soap, but I'll give my 2 pennethworth. !
The band around a Norton clutch is intended to keep oil out of the clutch plates.
As long as they are not flooded in oil, they work perfectly satisfactorily without the band at all.
A trace of oil on the plates is not the disaster it once was.
Norton clutches came in 3, 4 and 5 plate versions.
A 750cc would need the 5 plate version if you expect the clutch not to slip.
A 350cc might get away with 3 plates, but you'd have to be able to assemble and adjust it OK.
Binding when you do up the retaining nut usually means the clutch basket is rubbing on the bushing in the high gear bizzo,
maybe even pulled up hard against it. You may need some sort of washer or spacer to hold it out slightly further on the shaft.
Could be the clutch is machined slightly differently or deeper than the original. This MUST be corrected.
How is the chain alignment. ?
Hopethishelps.
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The BSA six spring clutch on the B range (not the A's) was a shameful piece of tin pressing, and the band is to stop the basket distorting in use. The number of plates (and hence the depth of the clutch centre) varies between the 350s and the 500's, the larger bikes using more plates.
On yours you should be able to use the lower number of plates, which is good as it makes for an easier clutch pull. You'll need to set up the outer plate truth to a fine degree if gear engagement is to be anywhere near silent. A DTI is good for this.