That is one nice New Factory K1!
The fork ears are K2 or later, which you've already surmised. They probably got bent when the incident that broke off the steering stop happened, which likely also bent the tank, hence its repaint. You might find either some 'undent' work (or Bondo?) on the side of the tank opposite the broken steering stop. This too-far-twist often damaged the wiring harness right at the steering head, too, so that might account for the new harness?
The K1 had a particular issue when the New Factory started making the frames with the increased-strength lower bolsters for the engine: they forgot to provide a path for the water vapor that accumulates inside the frames to find a way out, as the new bolsters were fully welded shut. There was a recall notice to add a small (3mm or 3/16") hole in the bottom of the frame cradle, just behind the front lower engine bolsters, to provide ventilation. Here in the US, our (then new) high-pressure carwash sprays would force water into the frames, back above the driver's footpeg mounts, and it would collect behind the bolsters, rotting the frame. I drilled many holes there, and occasionally still do! (It was hard to forget, as the bike had to be held over on its side by 2 shop employees to allow a long electric drill to get access to the frame sites...)
Hey,
Thanks for your comment, it`s entirely possible that the chain of events happened just as you described. It`s weird though that if they fixed everything and even repainted the tank, why did they not replace the triple tree?
I`ll take a good look at the frame around the bolsters for corrosion. What exactly do you mean by New Factory?
It's sort of ancient CB750 history now, but the first factory that made them did most of the work by hand or semi-template work. The heads, for example, were all hand-ported in all of the engines that came from this Factory, and the rest of the work exhibited less-than-consistent work, bike-to-bike. But, these were also the ones that developed the most power, so they became coveted and searched for by 1971. These bikes were the first production bikes to routinely reach 100,000 miles (despite the few BMW R60 bikes that could make the claim back then, but at great expense to their owners) and, if they did not suffer the chain-thru-the-cases from less-than-expected (by Honda, of the owners) maintenance, they became legend by 1970. They were so incredibly popular that they were sometimes sold for as much as 3x their normal price (for which Honda would revoke the shop's Honda contract, immediately) and became the most-stolen bike in history (until the CX500 replaced that record in the early 1980s).
By 1970 Honda decided to build an entire New Factory, building just CB750 bikes (at first). They got it started by mid-1970, with the K1 becoming the first ones from that site. they suffered some growing pains from using templates for everything (so their 'corrections' were not real pretty), but by mid-1971 the entire output of this place was CB750. Their appearance became more consistent bike-to-bike, with the usual Japanese drive to make everything exactly the same to simplify assembly, while their engineers worked on making the bikes more reliable (an oxymoron?) by taming them down a bit, so as to help reduce their high warranty costs. Keep in mind, nothing like this bike had ever been done on a mass-production scale before (despite those Arial Square Four, Indian Four, and FN's 4-cylinder 2-stroke bicycle, all hand-built, limited-production items) nor had anything ever had such a market impact in this field: Americans proved to have a real knack for destroying them within their 90-day warranty period - usually by abusing them harshly. After all, they could take the neighborhood's Harley, Mustang, Camaro, Charger, and even Corvette by 3rd gear (110 MPH), and people literally stopped and stared at them as soon as they saw 4 pipes on the front. I lost track by 2 months of how many people at stoplights (we didn't have lots of air-conditioned cars then) would yell out, asking me, "Hey, what kind of motorcycle is THAT?", and other such things. By the K3 model, Honda had resolved to completely change how their bikes would be made, making the most advanced injection-mold machines for first the 750, then the 550, then the 350F/250F and the CB360 twin engines. Those became the forerunners of how all motorcycle and most car engines are made today, if made from aluminum or magnesium cores.
But, the New Factory bikes lost some of the 'personality' that could be seen by the handwork that was used to fix up [this or that] defect on a 750, making it deemed adequate for sale without tarnishing Honda's image, which was a very sensitive point then. I have an Old Factory K2 (my first 750 was an Old Factory K1, with many problems) that was finished in 11/1971, using a K1 Old Factory engine that had failed QC somewhere along the way, then went back for remedial work, and came back to the production line during the beginnings of the K2 series. While this engine dropped right into the chassis, the rear crankcase breather (originally 6mm size) had been removed and replaced with the larger 8mm version, the left-front engine bolster was hand-fitted to the 1mm narrower K2 frame cradle (looks like with a file?) and the K1 footpegs and mounting bolt/nuts were used on the otherwise K2 frame setup. It also came with the #657A series K1 carbs, probably because the cam is K1, but since the exhaust became the HM341 quieter pipes, the AD125 Hitachi spark advancer was installed (instead of the newer TEC version) to try to help keep the plugs clean. This ultimately failed, leading me to rejet later and recurve the advancer springs, but in the end it got more power than almost any other K2 around me which became apparent when I could take another K1 or K2 on the street, despite toting a Vetter fairing from day one on this bike. This was part of how the 'Hondaman' legend got started (thanks to other 750 owners of the area). In truth, it was just about knowing how Honda had made them.
