G12 crankshafts

zwarts · Post by **zwarts** » Sat Feb 25, 2012 11:04 pm

"P.S. Bob: Have you written any service manuals for AJ's?"
No, I haven't the time! There are plenty of manuals available already, mostly written by Fred Neill who was the works service manager at the time these bikes were made. The drawback with manuals is that they cannot anticipate the sorts of question which crop up here. I am also a firm believer that there is no substitute for the practical experience gained by working on these bikes yourself and then using them as intended (or, in my case, perhaps not as the makers originally intended!). If you have a good grasp of the four stroke cycle and some basic engineering knowledge then there's nothing else that logical thinking and common sense cannot solve with these comparatively simple engines!
Cheers, Bob.

Oldun · Post by **Oldun** » Wed Apr 04, 2012 6:58 pm

I should point out that the X in the engine number doesn't mean a factory replacement engine.
My 1960 650 CSR has an X in the numbers and when I asked Les Ward at the OC for a dating cert, I asked about the X. I was told that all twin engines of the period had an X.

laxy · Post by **laxy** » Fri Apr 06, 2012 7:37 pm

groily post of feb.11th is interesting.If the engine no. has an X in it then its not the engine that left the factory in that frame? Would the number stamped on the crankcase be the same no.as the original engine no? If so a lot of "matching numbers " bikes have been sold over the years that have had an engine transplant, all be it by the factory

laxy · Post by **laxy** » Fri Apr 06, 2012 7:49 pm

I think the mystery of the X in the engine no. needs clarifying.A lot of people, NOT ME! have paid top dollar for a matching no. bike that might have had a replacement engine fitted.Also the seller might have acted in good faith but has sold a bike that did not leave the factory as a complete unit as far as the engine and frame numbers are concerned

les ward · Post by **les ward** » Sat Apr 07, 2012 9:08 pm

The Factory records for circa 1960 show the X on twin engine crankcases were present at the time of initial dispatch and are the original crankcases.

The only archive material I ever saw, when I was machine dating officer, regarding replacement crankcases was an AMC invoice and that showed that the replacement engine with new crankcases (following crankshaft breakage)was dispatched unstamped.

Groily · Post by **Groily** » Sat Apr 07, 2012 10:38 pm

And I think the groily post of Feb was wrong and he has to grovel. I had fallen for folklore, convincingly delivered, in relation to a set of cases in my own shed.
Sorry to have confused myself, and doubly sorry to have done same to anyone else. I now reckon the '61 motor I have (complete with X) is correct for the frame it was with, but I haven't gone through the proper hoops to prove or disprove it (not worth it for that rather bitsa beast).
Proper investigation would, I am sure, bear out 100% what Les says!