Hermit, so the first TED RDC I scrolled down to was
RDC (99-2251) 1974 750 #100174 page 35
ref. # 13. 57-4550 listed the correct part number is 57-4791

Good luck trying to do that! 57-4791 is wider and has the groove
for the locating circlip used in the later iteration of the layshaft.

57-4791 is used with the 57-4900 5 speed layshaft. Please note that the related parts for the early layshaft are also listed improperly.

All of my references have been written in my parts books, and cover more than was given to us in the addendum sheets. If you want to come down and copy them your more than welcome.

I live by Henry Fords words: "Never complain never explain. But I make exceptions. "At 82 my work load still includes working 7 days a week (one quarter of a day Sunday). Now that I am semi-retired I typically work half a day monday thru saturday: That's 8am to 8pm. This includes servicing over 300 dealers for Triumph, Norton and BSA parts and over 1,000 Vincent customers. Writing software for our business system and maintaining 2 Linux servers. We also publish quarterly magazine: Vintage Bike for the TIOC.

With the Covid we are short staffed and the staff we have have been working 60 plus hours a week. What was a stressful business has become even more so. We are constantly chasing shipments. Customs has become a nightmare. Having to arrange for shipments be trucked from Europe to the UK because freight rates from Europe have become punitive and now with Brexit freight is not getting out of the EU into England.

We have had more shipments lost in the last year than we have had in 50 plus years of business. Collecting insurance monies for thousands of dollars can take 3 to 4 months and then only if you stay on their case. Meanwhile you are out of product.

And then the phone rings and someone want us to explain how to time his magneto on a Vincent, or diagnosis his electronic ignition, that has never changed a light bulb...