C25 Clutch Conundrum

[Andy Edwards]

Hello. Hopefully someone can help me with this.  I am still rebuilding the 1967 C25 engine that I stripped down many years ago. I have reassembled the clutch using a new clutch drum, plates and rollers.  There are however a couple of issues:

1. I cannot fit the new clutch springs that I also ordered. The original springs were approximately 35mm long and the new ones are 42mm. The spring cups are 7/8" deep and it is not possible to compress the new springs into these cups without the springs becoming coil bound!  The clutch was working ok when I last rode the bike. Checking the Draganfly website, they list the spring cups that I have 40-3218 as 7/8" long for production years 1967-1969. They also show 57-3951 Spring Cup at 1+1/16" long.  They only list one spring though, 40-3231, 1.75" (44mm) in length for use in all years of production. This doesn't seem to make sense to me.

2.  Only one clutch hub is listed for all years of production, 40-3207.  With the clutch fully assembled with the original shorter springs and the spring nuts incorrectly screwed in fully as far as they will go, the ends of the studs are still 5mm below the face of the spring nuts.  This means that I can use a normal screwdriver rather than the special forked tool to tighten these nuts.

Does anyone have any thoughts about what might be wrong?  Like I said, the clutch was working OK before I stripped the engine.  I guess that I could just rebuild it as it was!

[rhyatt]

try Kidderminster motorcycles
great for BSA
01562-66679 maybe they can measure the springs for you

[Andy Edwards]

I think I've got to the bottom of this.

I'm not sure how I missed this but page 268 of the excellent Rupert Ratio book shows that in 1969 BSA shortened the length of the studs of the clutch centre and compensated by lengthening the spring cups. It seems that I have the later clutch centre but the earlier spring cups!

This information is not reflected on the Draganfly website.