Wow this is the real deal 1968 prototype CB750

[AshimotoK0]

https://www.cb750prototype.com/

[Bryanj]

There are a couple of diferent posts about that recently on the US forum Ash, what they say makes sense to me in that a running prototype would be there before a pre full production set sent out to tease the dealers but not sure about Honda leting that out of the factory first

[Laverda Dave]

Some amazing history and early engine photos in that article. Thanks for posting Ash, great read👍

[K2-K6]

Very interesting Ash.

Makes sense that they took it there as soon as something tangible was available to show, what with history of them in USA Honda network asking for a multi cylinder engine to advance from the 450 twin as request from marketing position etc.

The notes say "only CB750" to use accelerator pump on carbs .... probably don't know about the F2 then, and also Keihin made 

Interesting about having a Hyvo primary chain on that one only too. Last development of this bottom end, going into RCB racer, went to gear primary drive with a idler intermediary gear to keep the gearbox rotation in same direction too.

[AshimotoK0]

The notes say "only CB750" to use accelerator pump on carbs .... probably don't know about the F2 then, and also Keihin made 

Yes I though that too .. very complicated carbs too yet the 4 pre-production prototype bikes had 4x modified CL77 carbs sprayed with silver paint!

Not seen anything about the way he came by it ,which is a bit of a shame... but early days yet I suppose. Always nice to know the history after it was shipped to the USA. I guess it must have gone back to Japan at some stage but that's only a wild guess.

[K2-K6]

Interestingly, the combined float bowls are seperate in function, having discreet volume for each carb, but seem to be used as mounting to give structural component (later a dedicated carb "rack") along with a beam across the top of carbs to make a competent assembly.

Placement of anything PRE marketplace is, as I understand it, subject to tax and import regulation for which a temporary waiver is given, after which the item (s) have to be either removed from the country, or destroyed for disposal (being cheaper) to ultimately comply with their temporary import.

Guessing that some of these vehicles escape by someone hiding them away as they think it's too much of a waste, on a personal level, to really scrap them. Interesting that some are kept, understandable that the stories are deliberately obscured. Technically the IRS could still come for the demands of import be met, although out of time status likely to apply now. In taxman terms, they'd probably want to see it crushed 

[Spitfire]

Fascinating, and amazing that it survived, though the full story would be even better.

Cheers

Dennis

[AshimotoK0]

Interestingly, the combined float bowls are seperate in function, having discreet volume for each carb, but seem to be used as mounting to give structural component (later a dedicated carb "rack") along with a beam across the top of carbs to make a competent assembly.

Placement of anything PRE marketplace is, as I understand it, subject to tax and import regulation for which a temporary waiver is given, after which the item (s) have to be either removed from the country, or destroyed for disposal (being cheaper) to ultimately comply with their temporary import.

Guessing that some of these vehicles escape by someone hiding them away as they think it's too much of a waste, on a personal level, to really scrap them. Interesting that some are kept, understandable that the stories are deliberately obscured. Technically the IRS could still come for the demands of import be met, although out of time status likely to apply now. In taxman terms, they'd probably want to see it crushed 

Sounds spot on to me Nigel. Vic World was at DS 750 event and was very approachable and a totally unassuming guy, when I talked to him.

BTW I think the CB750A Hondamatic SOHC 750 had a Morse Hy-Vo primary chain.