Primary Chain Case!

[LJ.]

Last Thursday (July 13th) friend and self went down to Brighton from Peterborough UK, to pick up his new Enfield. Almost got there and BANG!  > The primary chain snapped! What a mess!



Got home courtesey of Carole Nash Insurance, no problem. The 4th day after it happend I have a new case, now I need to order clutch drum today and hopefully will be back on the road after the seventh day, which is not bad considering parts are sometimes hard to get.  8)


I really dont know why the chain should have snapped,  ??? I only replaced it three months ago. My friend and I think that it may have been a low stress chain only suitable for conveyor belts or such like. This time I have a Reynolds and I shall be keeping a very close eye on its performance.

One thing I am concerned about... The clutch drum/or basket, is it acceptable for it to be slightly wobbley?  ??? I would have thought NOT! but some guys say that they are all like that. My friend has discovered on his B31 that the friction plate should go in first rather than a plain plate as this then takes up that wobble/slack. Difficult to describe here in text. Hope you catch what I'm trying to say. I know that the drum and engine sprocket should be in line so the chain can hook neatly.

Well....guess I'll just have to get out there and try it.

[dpaddock]

Bummer!
Yes, the clutch chainwheel is wobbly. And, assuming you have the factory six-spring clutch, the first plate into the basket is a plain (driven) plate. See Plate 4, p.23, in the Spares manual.

[Caretaker]

Bad luck, but good to see the damage was somewhat contained! & thanks for sharing your excellent photos and description, & hope your problem is nicely sorted out by now. A good reminder to keep checking things on the bike now and then, and to only buy & use the best parts one can find. And, yes, my 6 spring clutch is wobbly too (not extremely...) but alignement is fine and, my chain has lasted a long, long time with no sign of wear... so I should probably change it soon!

Regards
Erling

[dpaddock]

Pitchline velocities in primaries are 'way beyond recommended limits for standard chain, which is why one must always use Renold or another chain built for motorcycle primaries.

The chief cause of chain failure is tightness, assuming lubrication and alignment are correct. I run my chains loose, almost slapping the case.

As for Erling's concern about wear: up to five percent stretch is permissible, although I use two percent, especially in the primary. Abrasive wear is obviously not a factor here. A quick indicator is to observe the sprocket teeth. If they're "hooked", they're worn and so is the chain. Replace both chain and sprockets. (Generally the drive sprockets wear more quickly than the driven.)

Best,
D/

[fido]

I've never had one break but I used to find a handful of broken rollers in the bottom of the chaincase on both the A7SS and the B31. My 1948 bike has a nice duplex chain which has never given any trouble  8)