Topic: Honda CB750K1 Engine numbers.

[aussie cb750 k1]

Concerning engine numbers for the K1 Series....does anyone know if any of this series only had (6) digits in the engine number.For example....CB750E123456 or should it be 1123456.My bike has only (6) digits after the CB750E.

I'm wondering if the cases have been numbered incorrectly after the previous owner threw a chain,smashed the cases & bought new ones that of course are unstamped & left the (1) off after he punched in CB750E-( )123456.All these engine numbers should have 7 digits,,,,is that correct???

[Hinomaru]

Welcome to the forums. 

I don't know why you have a 6 digit engine serial number, but I'm assuming you have an Australian market K1 (area code U). If that's the case, then the correct 7 digit serial numbers for Australia begin at::

CB750E-1044806 (engine) and CB750-1054244 (frame)

Reference: Honda publication



The USA market 750 K model engine serial numbers also have 7 digits and look like this K2 example:

[aussie cb750 k1]

I appreciate your reply & the effort you went to.My bike is 9/71 K1 that is an import from the US.The engine numbers have been stamped with ordinary workshop punches & are not the same typestyle as your sample K2 numbers.
Me thinks these are a new set of cases supplied by Honda after a chain breakage,much like the early Sandcast model.However when I started to strip the bike I found it had an endless chain fitted,so chain breakage and smashed cases might all be the answer.The bloke who owned the bike might have mistakenly left off the first digit.
All that being said however,there is a K1 on Trade Me (much like Ebay)in New Zealand,the owner of which is the fifth owner & who works in a Honda shop in Hastings.This bike has (6) digits on the engine number after the CB750E.So what gives???

[Hinomaru]

Well, I did some further research and checked the Honda published reference for engine & frame serial numbers from the following markets that the 750 K1 was sold in:

USA
General export
England
France
Germany
Netherlands
Australia
European direct
Japan

The engine serial numbers from the above markets all show 7 digits and they all have this format: CB750E- 0000000 
I don't know why a 6 digit engine number would be used and that's a bit of a mystery. Since there are now two K1's with 6 digit engine numbers, perhaps another forum member can come forward with a plausible explanation?