Seems like a 750 serial number on an 850 (2008)

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grandpaul said:
A guy on fecebook posted this one...

Seems like a 750 serial number on an 850 (2008)


He included this caption: "This engine I bought as a 750 short stroke, also with 850 cylinder block. Numbers don’t seem to be far away from the other engine, but this one without the extra number and rondelle."

MAYBE THE POSITION OF THE STATOR STUD HOLES IS A CLUE?
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Those 850 style cases look like a bad doctor job to me. So initially I'm skeptical. The machined surface marks on the pix above are straight... and run from 2 oclock at the top down to 8 oclock. I have over a dozen engines 200k+ and NONE show those kind of marks.

Any 200K+ thru the end of MKIII engine that has not been "doctored", has machine marks on the sn boss that arc . as if the center of the cutter swing originates from the center of the crank bore. The arc of cut radius is 4 to 4.5".
It is called a facing process. It's a fancy boring head.
 
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dynodave said:
Those 850 style cases look like a bad doctor job to me. So initially I'm skeptical. The machined surface marks on the pix above are straight... and run from 2 oclock at the top down to 8 oclock. I have over a dozen engines 200k+ and NONE show those kind of marks.

Any 200K+ thru the end of MKIII engine that has not been "doctored", has machine marks on the sn boss that arc . as if the center of the cutter swing originates from the center of the crank bore. The arc of cut radius is 4 to 4.5".
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Curiouser and curiouser...
 
So what is the verdict on 850s with a 235xxx plus 1 engine number ?
 
Another one, from the "Seen on e-bay" thread. dodgy/bodgy stamping job...

1610906424807.png
 
Does seen odd but the faint numbers behind seem to be the same characters but the faint 5's look smaller as if the first attempt was a test or a way to faintly mark them while waiting for a proper sized 5 to turn up.
 
I'm fairly satisfied the OP 235 bike is NOT an 850 as the numbers and "850 style" barrel and actual 850 cases are exactly what you would expect for a SS750.
If someone strips the SS crank, rods, pistons, cam, RH7head or RH8 and fits stock 850 guts back in, what have they gained ? .....big time...... a SS750 kit for $0
and what ever they sell the residue for

On GP post 65 you can still see some residue of the original long sweeping facing cutter marks, so the face IS original to the cases.
 
kommando said:
Does seen odd but the faint numbers behind seem to be the same characters but the faint 5's look smaller as if the first attempt was a test or a way to faintly mark them while waiting for a proper sized 5 to turn up.
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the data plate and trans match . I think the engine stamping is factory . Heres a theory; it is messed up because the normal 850 stamping process was not followed . Maybe a different person? Probably because of the unusual number.
 
dynodave said:
I'm fairly satisfied the OP 235 bike is NOT an 850 as the numbers and "850 style" barrel and actual 850 cases are exactly what you would expect for a SS750.
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However, it has an RH10 head. Other 235 850s have the long stroke.

I get the feeling that the supposedly 200 short-stroke engines were rebuilt as 850s when they reached the US as the short-strokes were never intended to be sold to the general public.
 
L.A.B. said:
However, it has an RH10 head. Other 235 850s have the long stroke.

I get the feeling that the supposedly 200 short-stroke engines were rebuilt as 850s when they reached the US as the short-strokes were never intended to be sold to the general public.
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When homologating for racing purposes, surely the factory didn't keep all 200 examples, would they? Then, any that were sold to privateers is the same as general public (except they may have also been raced)
 
grandpaul said:
When homologating for racing purposes, surely the factory didn't keep all 200 examples, would they? Then, any that were sold to privateers is the same as general public (except they may have also been raced)
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That is the question, as short strokes were supposedly available in Roadster specification or, that's what the brochure suggests.
Seems like a 750 serial number on an 850 (2008)


The limit stamps look original which suggests they and the '1' are factory stamps.
 
I was trying to arrange to buy the bike but was too late...anybody here get it?
 
When someone finds out WHO these 200 bikes were homologated for USA / AMA ?. World wide available or USA available as a complete bike only ? What were the rules back then? Then they woud have gone through Berliner OR norton west california to a US dealer then to the race bike builder. I can't imagine a serious racer with only one engine. 3 or 4 engines maybe one or twq rollers.
Ok you got 200 in the US and racers do NOT want a bike, they want the engine. So they buy the bike to get the engine and sell the carcass. Maybe the dealer was the engine swapper, then sell to racer. What are you buying today? A left over carcass with the number of a SS750 and an 850 with a RH10 head?

A complete running bike , engine removal, complete disassembly, reassembly , back to running bike is done in 12 hours or less. I've done it...around 2003 on my friends 73 850 when we fixed the Fraterelli rebuild. It actuall took longer than it should have but since we found the internals had been sand/bead blasted and was doing the nasty to the expensive rebuild. We has to scotchbrite all the case internals. It is still running today.
 
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grandpaul said:
Another one, from the "Seen on e-bay" thread. dodgy/bodgy stamping job...

View attachment 21117
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I’m looking at a Craigslist ad for this one 235592 in Morgan Hill, Ca. I recall years ago a comment that these 235xxx may have been factory recalled machines. Now seeing both engine sizes. If the case it’s no wonder there is no factory production record. In sales of anything these would then be “seconds”.
 
illf8ed said:
I’m looking at a Craigslist ad for this one 235592 in Morgan Hill, Ca. I recall years ago a comment that these 235xxx may have been factory recalled machines. Now seeing both engine sizes. If the case it’s no wonder there is no factory production record. In sales of anything these would then be “seconds”
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If the bikes were returned to the factory and rebuilt with new cases then I can't see how they could be classed as "seconds"?

If they had been factory recalled then they must have already had 235 serial numbers to begin with as there would seem to be no logical reason to change serial numbers from 3xxxxx as that would have involved changing the crankcases and gearbox. These 850s so far, seem to be in the 235500-2356?? serial number range and built in early '74 according to the frame plates and frame '*850*F' serial numbers.

Would the factory have bothered to ship those apparent "seconds" back to the UK and then back to the US again?
Shipping them back to the US with different serial numbers must have required documentation in my opinion.
Any apparent rebuilding would most likely have been done in the US, in my opinion, possibly by the importer?
 
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Strange how these bespoke items appeared to pass through the hands of the Stuttering Stamper!
 
L.A.B. said:
If the bikes were returned to the factory and rebuilt with new cases then I can't see how they could be classed as "seconds"?

If they had been factory recalled then they must have already had 235 serial numbers to begin with as there would seem to be no logical reason to change serial numbers from 3xxxxx as that would have involved changing the crankcases and gearbox. These 850s so far, seem to be in the 235500-2356?? serial number range and built in early '74 according to the frame plates and frame '*850*F' serial numbers.

Would the factory have bothered to ship those apparent "seconds" back to the UK and then back to the US again?
Shipping them back to the US with different serial numbers must have required documentation in my opinion.
Any apparent rebuilding would most likely have been done in the US, in my opinion, possibly by the importer?
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I see your point. The fact that 235xxx was used on both standard 750 and 850 machines is still a mystery. Speculation the 750s were left over material after the April ‘73 stoppage of 750 production. For the short stroke 750 was there a way to physically distinguish the cylinders from standard 850 such as one cooling fin less?
 
Old thread
Well done by lcrken -thanks

Short Stroke 750 Build

Well, I've been inspired by the build threads by Paul and others, so I'm starting my own. I'm just starting the rebuild on one of my short stroke 750 engines. I originally built it as a mild road race engine for AHRMA Formula 750 racing. After a fair amount of that, I freshened it up a few...
www.accessnorton.com www.accessnorton.com
The hard ware is not in question (by me anyway) the article does answer "some" of my questions. There may have been 2 different factory SS engine at different times .
Still gone elsewhere for more data/details.
 
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