I am in the midst of restoring my CB750 K1 (4/71, 1089xxx) and discovered it has a two hole rear hub. The hub has a 13 followed by a 6 stamped on an internal face if that means anything.
My question is this; reading comments made on these forums, two hole hubs came on KO bikes. Is it possible that my K1 came from the factory with this hub? The only changes to the bike I have identified is a post '71 drive hub with studs rather than bolts and a Harley 16' rim.
I can trade/barter with a local that needs a two hole hub. He claims the K1's only came with 4 hole hubs. If this is true I can most likely obtain the correct K1 hub and drive hub. Is there anything to identify a K1 hub, other than 4 holes?
If I go ahead and do this, assuming it is not correct, should I be looking for extra$ on the exchange?
Thanks in advance for any information.
In the build era of the 750/50/550, Honda frequently recycled parts in their processes.
It went something like this:
4/1971: a 750 engine (or cases) failed QC, needed some work on #2 crank support, like maybe the bearing hole was not bored just right during the align-bore step.
6/71: The engine was recycled through the Engine Department for correction of the 'bad' part (or machine steps) and someone judged the best way to fix it, then it was fixed.
7/71: The engine (cases) put back into the Production Process, and scheduled into another bike build.
The above actually happened to my own 750K2 engine: it started out as a K1 engine, ended up in my early K2. Along the way, the engine serial number was ground out and welded in, then restamped, so I am supposing it got further than just cases only before some defect was identified. (I first noticed this in 1980 when I stripped the paint from the cases, before repainting them - which filled in the tiny edge-of-welds marks in the serial number 'window'). Inside the engine, the #2 crank main bearing support has 3 stamped-in QC marks, and it has a bearing shell one size larger than the others. Since the engines were bored left-to-right, this would seem impossible except for some sort of rework step.
During the years when I actively 'tracked' such things, I came across 2 other 'early' K2 bikes with serial numbers close to mine (...#4530). One was earlier (I think it was ...#4520-something), and had a K1 engine also, the other over 150 numbers later, and had the K2 engine. Many other examples of this sort of 'exchange' of parts abound on these bikes. Even during the K5/K6/F0 era, the engines swapped heads and cylinders, and cams and pistons, a lot. It's not real unusual to find, say, a K6 with pop-up F0 pistons and a K5-era cam: these are real hotrods that develop somewhere around 10.6:1 compression, and the carbs will have #110 mainjets inside. Every now and again you will hear of these 'legendary' K6 bikes.
