learn something new every day

I installed a new countershaft sprocket on an unknown 71 Norton. After putting everything back together and installing the chain I discovered the chain had a catch to it. Nothing was obvious so I pulled off the entire primary and its contents and discovered the new sprocket allowed for NO side to side play on the chain. A stock sprocket is .350 thick, the new one is .377 thick. #&^%(&^$%$%*!!!

seattle##gs said:

I installed a new countershaft sprocket on an unknown 71 Norton. After putting everything back together and installing the chain I discovered the chain had a catch to it. Nothing was obvious so I pulled off the entire primary and its contents and discovered the new sprocket allowed for NO side to side play on the chain. A stock sprocket is .350 thick, the new one is .377 thick. #&^%(&^$%$%*!!!

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Ouch! Where did you get it? I wd never have thought to look at this in advance either...

I am working on someone's Norton and he provided the sprocket. It looks somewhat crude compared to the original which is stamped "made in England". I am going to take a disc grinder to it today and thin it out. Has to be hand held, I couldn't grab it with the lathe jaws.

seattle##gs said:

I am working on someone's Norton and he provided the sprocket. It looks somewhat crude compared to the original which is stamped "made in England". I am going to take a disc grinder to it today and thin it out. Has to be hand held, I couldn't grab it with the lathe jaws.

Click to expand...

Won't grinding it remove the case hardening? I guess it was made east of the Watford gap!! Might be worth checking the back of the sprocket to see if it runs in the gearbox seal properly

I didn't think about the case hardening. I will not be grinding on the teeth themselves but on the sides. Think that will shorten its life?

looks like the sprocket is of inferior manufacture, return it to the guy who gave it to you and let him know his new part is not acceptable, and he should return for refund/replacement , don't grind it then you just bought it...

the new tecknology is to surface harden the sprocket, so once you break through the surface hardening its just butter inside.... i got a very derogatory response from my local vendor and his fabricator/supplier when i questioned why their new sprockets were not hardened like the original one which needed replacing(rockwell c60+) I tested both. the new ones are now only surface (case) hardened, i guess there is a cost saving and possible quality advantage with the new process. the surface hardening will go a long time (claimed 40% long life)but once it is worn down, the teeth will fail in short order.

the made in england supplier ifrom whence my sprocket was supplied is Velocette Motorcycle Company

IF you really want to grind it and get it moving, I suggest you put it in writing, that customer supplied the part. So when it fails...
The mechanic who works my wife's car won't even accept parts I bring, unless he knows where they came from.

the original sprocket on a 71 would be 19 teeth... I think you will find 'made in england ' means norvil , you could try them for another or RGM

I ordered a new 20T sprocket yesterday.