Honda changed the seat many times on these bikes, specificaly to deal with this ride height issue.
The K0 had bold, wide, (beautiful) squared-off side covers and a lowered section on the seat where the rider sat, about 1/2" lower than the passenger. In some parts of the U.S., the dealers were REQUIRED (some say by Honda, some say by lawyers...) to measure a customer's inseam before selling them a 750. I was measured both times for my K1 and K2 (when some guy tapes your inseam, you don't really forget that...). The K0 required most riders to slide forward a bit and put the legs down in front of the side covers to be flat-footed. Dealers trained customers on this, if their inseam was less than 31", and would not sell a 750 to them (in the Chicago area) if the inseam was less than 30" (honest!).
The K1 had new side covers with a rounded top edge (and the oil tank had to be redesigned to accommodate it, and the electrics moved inboard of the frame toward the battery a little bit). The seat was wasp-waisted a little right at the tank, to make it feel narrower. The ducktailed seat disappeared on the later K1 (after about 9/1970 production), and the seat lost its "stepped" look, with the whole seat then being the same level. The drawback to this was that the passenger end of the seat got thinner by almost 1", and this put the thickness of the pad over the rear rubber block at only 1" in a small center area of the seat. This remained until the end of "K" production, but spawned a whole 750 custom touring seat industry!
The K2 added a scooped-out slab on the seat, just aft of the tank, and the bead on the upper seat cover piece followed the line of these scoops, which made the narrowest standing stance of all the "K" models. Trouble was, though, the rider's bluejean leg seams were scraping the paint off of the side covers, at the front top sides of the covers, right under this scooped area.
The K3 introduced the seat we called the "flat top" or "aircraft carrier" style. It's the one most often seen today, with a flat, one-piece top that has the bead all around the top edge. The front of the seat is narrowed right into the tank, almost making the top into an oval shape at that end. The whole seat sits flat and nearly level when the bike is on the ground, and it has a very squared-off look to the sides. This is the seat that remained to the end of "K" production, and is most commonly sold by Honda today if you buy their OEM seat. It does not feel as narrow as the K2.
I have replicated the K2 seat by taking the "modern" seat pad and scooping out about 1/2" of material with a serrated bread knife, just aft of the tank about 1" or so, extending back about 4" to 5", and halfway down the side of the pad. Then I make a seat cover with a top that follows this contour, flapping down on the sides so it lays nice and flat and does not wrinkle. One I made with the bead, one without. I really liked the one without, and now, when I make seat covers myself, make them without. They last longer and don't tear up the bead, making the seat look ratty. My current seat (which is stepped down too low in the driver's area since I installed the 12.75" shocks
) is shortly to be replaced with another K2 replicate that I'm about to make. Maybe I'll post pix of it along the way...
