Following on from Rob Millers posting about the frequency of failure of the gearchange return springs on an M20 (which is a rare occurence) a Norton was struck with this problem at the Buckfastliegh 40s weekend which I have just returned from.
Clive, the owner of the bike has broken two in 18 months and Riks previous posting indicated he has also broken two in a fairly short period...It seems it may be wise to stock up while originals are still available...On the plus side they are much easier to change on the Norton gearbox than the BSA one...Ian

email (option): ian@wright52.plus.com

Replacing a broke spring in a BSA M20 gearbox is a piece of cake. You only need a handful of friends with tools and parts to do the job, and of course about one hour of labour while being tortured by these same friends with their camera's and their laughter.

Henk

email (option): ahum@quicknet.nl

No,No,No...when an M20 stops the main thing is to get it running again as soon as possible...the cameras and laughter are for the Norton riders.. .. ...Ian

email (option): ian@wright52.plus.com

There were precisely four Norton riders on the campsite in France and none of us is the type to laugh at another's mechanical misfortune, certainly not when it is being repaired with such consumate craftsmanship.

So far I've only done the one return spring on the 16H. The AMC boxes seem to be harder on pawl springs.

An earlier post on here suggested that there was a problem with the NOS springs and that modern replacements are more reliable.

There is certainly a good case for having a spare handy somewhere in case they get harder to find but if the supply dries up then it's not too difficult to have made.

Maybe it would be a good idea to get the springs shotblasted, I believe that Daimler did this on their scout cars as they were suffering persistent breakages and as soon as they did this the springs didn't break, it could be something to do with the lines on the metal from where the wire is drawn. Blasting them supposedly stress relieves them, it may be worth checking a NOS one with a pattern one and see if the NOS one looks to be blasted

email (option): davmax@ntlworld.com

From memory Dave, the surface finish is quite linear and striated so that may be the problem. I'll have a look at a spare but I don't fancy cleaning cosmolene this evening !

BSA applied a ground finish to both valve spring and girder fork spring wire before manufacturing the springs, following problems with stress fractures caused by surface irregularities. I have not come across any documentation indicating whether this process was applied to other springs but it is possible. I think the problem with BSA gearchange return springs is more one of design. The entire ratchet assembly is a bit of a compromise as they enclosed what was essentially a hand change mechanism. The smaller of the two springs particularly is very lightly constructed and both springs can contact the back of the ratchet assembly during operation causing wear on the spring coils over long periods of use. Condensation in the outer cover and the resulting corrosion can also sometimes an issue..I coat the entire assembly liberally with graphite grease before fitting it to the gearbox..Ian

email (option): ian@wright52.plus.com

I haven't had any trouble on my 16H in the years since I got her on the road back in 1979. In those days you had to pass a road test on the RDW site near Almere ( speed, handling and noise < 85 decibels!) So I am still proud to have gotten away with that.
I must have done over 80K kilometers (I am now up to my 7th rear tyre) so either I was lucky, or teh Norton spring is okay.

I know for sure that it is far better accesible than the BSA one, with the small nuts on the backside of the front cover being absolutely inaccesible for anyone larger than a midget with very tiny hands!

Did you hear that Henk.....Rob recons your a midget....Mind you! You did only put three of the four back . Ron

email (option): ronpier@talk21.com