I have just noticed that the spring link on the engine drive chain of our ’58 Birmingham Scott is cracked, what size is this this ? and can anyone recommend where to obtain one ? also the chain seems very tight how much slack should there be ?
Don’t run the bike with the tight chain/cracked link !! This can loosen the drive sprocket on the flywheel, which is a total engine strip-down job to put right. To adjust the chain first slacken the two nuts holding the final drive outrigger to the gearbox tray, then the two nuts underneath the tray that hold the gearbox in place. Now go to the adjuster sleeve-nut on the rear right-hand side of the tray, and turn it anti-clockwise, which will push the gearbox forwards and so slacken the chain, to give you a good inch of up and down play in the chain. Tighten the two nuts under the tray, and then the two outrigger nuts. Recheck the free play in the chain.
This procedure will have tightened the rear final drive chain, which will then also need adjustment by slackening off the rear wheel spindle nuts and then slackening off the two locknuts on the adjacent adjusters, to allow the wheel to go forwards, then tighten the wheel spindle nuts and finally the locknuts on the adjusters.
Finally check that the back wheel is still in alignment, by means of a length of string or a straightedge placed alongside both wheels, about four inches off the floor. NEVER run the bike with tight chains……
“Sprockets Unlimited” can advise you on all things chain, and supply everything you need. Obviously the new link needs to be the same make as the chain, which would originally have been Renold, not to be confused with Reynold or Reynolds…
Many thanks for that, do you know what size the original chain was, and how I can tell if it still has the original ?
Richard Blackburn of North East Classics Ltd., can supply the Renold bits that you need. See inside rear cover of Yowl for contact details. The side plates of genuine Renold chains have the name stamped into them. The closed end of the spring clip on the connecting link should always face the direction that the chain is travelling in.
I’ve contacted Richard and he doesn’t supply the make of chain fitted to my bike, the markings on it are a “O8 B” on some links and what looks like a rounded capital ‘A’ within a circle, I don’t think this is the original chain as I have a copy of a letter from the previous owner to the SOC trying to source a new one as the original was badly worn, does anyone recognise these manufacturers markings ?
As the primary chain has been running very tight it is likely to be strained and stretched, and personally I would just fit a complete new Renold chain, and I think that it would be false economy not to. If the chain fails at any speed it can pile up into the front of the crankcase, jam the engine up solid, and even break the crankcase.
Renold 1/2″ x 1/4″, 69 pitches and connecting link.
I think Brian meant to say… 1/2″ X 5/16″ and not 1/2″ X 1/4″ which is the mag chain size on pre Brum Scotts.
Oops, however, magneto chain is 1/2″ x 1/8″….. The Flyer/Rep/Brum primary chain is Renold 4305 type.
Oops again. Can’t get anything right first time!!
Just to check is that 1/2″ X 5/16″ 69 links including spring link (i.e. 68 chain links + 1 spring link) or 69 chain links plus the spring link (so 70 in total) ? as Richard at scottparts.co.uk is suggesting 68 chain links plus the spring link ?
69 including the split link. The chain less the split link will always be an even number,( unless you also buy a cranked “link and a half”, that some makes of bike seem to need due to inadequate provision for moving the gearbox backwards and forwards ).