Honda CB750 Sandcast

FRAME AND ENGINE PAIRINGS

kp · 9 · 2420

kp

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Here is a discussion that may get memberS interest
A question that I would love to be answered is how many engines were produced/available when production started from day 1 and how were engines and frames matched. There must have been at least 200 engines in the inventory ready to be fitted as we see such variations between F and E numbers as acceptable. An interesting fact for us is what I will call variation clusters. If you study the directory (even for the small numbers we have) you see some interesting patterns. Look at the first 3 digit series in the ranges 1s 2s 3s 4s etc E numbers are relatively close. Go to the F5xxs and we have E numbers in the 7xxs We get to the early F6xxs and they come back close again. Later F6s and F7s and they jump up again When we arrive at F8s these are all over the shop. Then we get to F9s and the 4 digit Es start being fitted and we also see some wider variations This pattern continues unabated more or less through the whole sandcast run. What does this mean. Hmm I'm thinking it's because the engine production was ongoing but delivery was not regular Maybe a truckload or pallet of engines every few days. Last engine unloaded was maybe the first one fitted after delivery. We have these other oddities where a pairing is 500 or even a thousand out and the owners swear they are the original pairings. I owned a sandcast years ago that had a difference of over 400 and they were the original pairing. Who would really know but I would just love to have the complete answers to this dilemma. Input please fellas
If only Mr Honda would give us access to the records
Yabba Dabba KP


Steve Swan

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KP, this is very interesting!  i only gave it a cursory reading, but i will carefully read it to absorb what you are saying.  Thank you for this thread and let's hear other's ideas!


Steve Swan

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Here is a discussion that may get memberS interest
A question that I would love to be answered is how many engines were produced/available when production started from day 1 and how were engines and frames matched. There must have been at least 200 engines in the inventory ready to be fitted as we see such variations between F and E numbers as acceptable. An interesting fact for us is what I will call variation clusters. If you study the directory (even for the small numbers we have) you see some interesting patterns. Look at the first 3 digit series in the ranges 1s 2s 3s 4s etc E numbers are relatively close. Go to the F5xxs and we have E numbers in the 7xxs We get to the early F6xxs and they come back close again. Later F6s and F7s and they jump up again When we arrive at F8s these are all over the shop. Then we get to F9s and the 4 digit Es start being fitted and we also see some wider variations This pattern continues unabated more or less through the whole sandcast run. What does this mean. Hmm I'm thinking it's because the engine production was ongoing but delivery was not regular Maybe a truckload or pallet of engines every few days. Last engine unloaded was maybe the first one fitted after delivery. We have these other oddities where a pairing is 500 or even a thousand out and the owners swear they are the original pairings. I owned a sandcast years ago that had a difference of over 400 and they were the original pairing. Who would really know but I would just love to have the complete answers to this dilemma. Input please fellas
If only Mr Honda would give us access to the records

KP, fascinating observations.  your reasoning is as sound as any speculation that could possibly be made.  certainly reasonable to think engines were delivered in batches and not one at a time.  i suspect timing the foundry work was a challenge to coordinate with engine assembly and then complete engines arriving at the assembly line.  i would think it reasonable the foundry was at a different place than the engine assembly and of course in between assembly there were machine operations (not only on cases but also on many other parts) which i also expect were not all necessarily in the same places as foundry and assembly.  thinking through the process of what was involved to produce an engine from start to finish will probably help make speculation a bit more coherent....  if we could get a handle on date codes of various parts as well as pair Evins with specific production weeks as well as dates Evins were paired to Fvins we might even think we know more than we already think we do......  and then there's the matter of chassis parts production, chassis assembly.  at least we know from pictorial evidence the bare frame was lowered over the engine when that aspect of assembly took place.  where the engine/frame pair went from there likely was in the same or a nearby area where the rest of assembly occurred.  then we also had the issue of machined castings, in particular crankcase halves that had to be reworked before engine assembly could continue.  lots of variables and lots of factors.

one has to suspect there were different shops in the different factories.  there had to be foremen for the different shops and there also had to be factory foremen.  an then maybe one big kahuna who oversaw overall production.......


Sgt.Pinback

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Do we know the highest engine number in sandcast frame (not the later French ones) up to VIN 7414?
Cheers, Uli (Leonberg, Germany)


Steve Swan

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Do we know the highest engine number in sandcast frame (not the later French ones) up to VIN 7414?

Uli, i am not sure i understand your question.  to the best of my understanding, 7414 was the engine number.


kp

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Do we know the highest engine number in sandcast frame (not the later French ones) up to VIN 7414?

Uli, i am not sure i understand your question.  to the best of my understanding, 7414 was the engine number.
You win a cigar Mr Swan. 7414 is the last sandcast engine and exists in a members collection in Europe
Yabba Dabba KP


kp

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When I say last sandcast engine I mean last of the non French engines
Yabba Dabba KP


Sgt.Pinback

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Ah OK.
7414 is the last engine number.

What was then the last VIN ?
Cheers, Uli (Leonberg, Germany)


bojje

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Hi!
Since the seller could not or did not want to tell me the VIN E7414 came from we will probably never know the VIN. However, I have asked my contact at Honda Sweden to check in Japan if it is possible to get an answer of this question. This week I am up in north sweden for moosehunt and next week the rebild of #7258/7414 will continue. I expect it to be finished in about six weeks from now.
Kind Regards,  Bo from Sweden.