Newbie question

Hi everybody: My name is Dudley, I've been poking around the forum here for about a year now. I'm very impressed with the wealth of knowledge. Maybe somebody can tell me what is going on with the numbers on my bike. I acquired a 1974 850 Roadster last spring. It had been sitting "out behind the shed" for about 15 years covered up with a tarp. I couldn't pass it up. It had every nut and bolt that was on it from the factory. It was a little crusty, but not anywhere near what I've seen here on the forum. If and when I recover my pictures from my broken computer I'll post a picture of it the day I got it. Since then, I've completely torn it down and have a question about the numbers. In Roy Bacon's "Norton Twin Restoration" he says that the 1974 850 MkllA engine numbers started with 307311 in January of 1974. And it's a 6 digit number. The number on my engine case is a 7 digit number. What does that 7th digit mean? He also says that the first 850's numbers started in April of 1973 with 300000. If I can figure it out, I'll post some pictures. Can any of you guys tell me what's going on here?

Apparently there were some '74 models built with 235*** serial numbers!

I don't think anyone has come up with an explanation why, or what the seventh number is supposed to indicate.

Would it happen to be a Roadster with the "White with thick Blue and thin Red stripe" colour scheme by any chance?

235*** are 750 short strokes using 850 barrels and crankcases, steel rods, high compression pistons, 4S camshaft, big inlet valves with thin stems(RH7 head), 80.4 mm crank. 80 bhp (marketing figure of course). Very rare.

johntickle said:

235*** are 750 short strokes using 850 barrels and crankcases, steel rods, high compression pistons, 4S camshaft, big inlet valves with thin stems(RH7 head), 80.4 mm crank. 80 bhp (marketing figure of course). Very rare.

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However, a significant number of 235*** serial models appear to be standard 850s and 750s, not all 750 short strokes and ""235565" has already been identified as being an 850 model.


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Yellow_Cad said:

Well, I visited this Commando one more time and here is what I learned:

1) The stroke is that of an 850

2) All three numbers (plate, motor, and gearbox) all match (235565)

3) The number on the motor has a little round symbal before and after it and after the round symbal after it is the number 1 and then another little round symbal

4) There is smaller than normal (not much space at all) space between the top fin on the barrels and the lowest fin on the head

5) Many years ago this bike blew a head gasket. This was repaired but the silver paint on the head is very thick and almost certainly brushed on. This made me think that it might have been originally polished and painted during the repair.

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