Honda-SOHC

Is this one in any better condition than yours?  The teeth all seem to be intact if a little worn.  AFAIK the CB and CL mechanisms from that period are pretty much interchangeable (the part #'s are identical - 24610-292-030).

Might be worth picking up anyway for what's known as the pizza cutter selector part shown prominently in the fourth image.  Those things are the main weak point of the 450 gearshift mechanism and when they go, finding gears gets very hard.  Decent ones are very hard to come by now. 

In terms of getting the 72/77's to run, the kits themselves are pretty decent - although I have no idea quite how closely they replicate the original bits.  If the carbs are in decent shape, those kits will get you 90%+ of the original set up.

That said, steer clear of the air screws they supply in those kits; they're invariably the wrong shape and will make your life very difficult.  I stupidly swapped them on the CL77 and CA77 . . . should've realised from the fight the little o-rings were putting up with the air screws that something wasn't right.  Basically, they don't seal and so air is pulled in around the screws.

Eventually realised the air screws were causing the trouble, swapped back to the originals and everything settled down.  Last time I checked, Silvers had both the correct air screws and o-rings that fit on them.

To get the liners out, stick the barrel assembly in the oven.  The aluminium block expands at a faster rate than the liners, so once the oven's hot enough, the liners will fall out.  If you stand the assembly right way up (like it would sit in the engine) gravity will help pull the outer block down; you'll hear a thump when it goes.  Can't remember what the "right" temp is, but it's not all that high - 200 deg C or something similar should get you started.

Usual caveats apply: make sure there's nothing rubber left in/on the assembly - like the rubber rings that hide around the liners under the block (or the fin spacer plugs on the '750s) - and if you're doing it in the house, clean the whole thing thoroughly before you start.  Even then, it's probably going to get a bit smokey . . .

Refitting is basically the same process in reverse, but when you do it, put the assembly upside down so the block falls onto the liners as they heat up.  And if you're swapping liners between blocks, don't forget to check they seat properly and the top faces are completely flush.  You may need to skim the deck depending on how closely matched the liners are.  I tend to use the sandpaper-on-glass/MDF technique for that.

Just been looking through the extensive Chilton's motorcycle repair manual 1945-84 version because, well, reasons.  There's nothing in there that differentiates the studs.

Without any clear overhead images of the head, it's very hard to say what goes where.  Other models in the same family (like the 350/4, 400/4 and 750/4) had a couple of shorter studs in the front; the 750/4's were the outermost front (corner) two whereas the others were one in from the front corners.  The 650 seems to be the odd-man-out and none of the images I could find showed the top view layout clearly enough. 

If I had to take a guess, I'd start with the two rear outer corner holes (carb side).  With the exception of a couple of the inner holes, the stud holes at the front (exhaust side) are shared with the spark plugs, so it's unlikely to be any of those.  If all 8 of the holes that are only accessible inside the head have the same floor depth (I have no idea whether they do or not), the logical place for longer bolts is in the only two remaining holes, being the outer rear corners.  Looking at images of the underside of the head, those holes also have spaces for knock pins.

That said, 2cm is a fair old difference in length and not something that's going to go unnoticed if you get it wrong - those longer bolts should sit up if they're in the wrong place.  I'm assuming you've already assembled the engine dry to see how the bolts feel in different locations . . .  it should be fairly obvious where there are a couple of deeper holes.

Cool.  Good work.

Don't be too hasty with the second one.  Honda used a variety of different key blanks, so only certain keys will fit certain locks.  If you can't get your key in, it's almost most likely to be because the spine of the key has a different slotting along its length.

Since the tooth pattern isn't all that complicated, you probably found a magic pairing with your old key and the enclosed lock.  I've got around 10 different keys across different models and the number of locks they fit into varies, but no one key fits every lock.

And if you get the lock out intact, you can always sell it - there's usually someone looking for a steering lock barrel to match their ignition/seat set, especially if you can read the numbers.

In the second picture, you can see the lock and the yoke mount it's in are different colour metals.  What you need to do is get the lock to turn so the little retaining pin lines up between the two mount sections and the whole barrel will pull out.  If you can read the lock number, your best bet is to find a key, otherwise you'll need to drill in from the front (i.e. through the key slot) and then turn the barrel once the lock mechanism inside is busted.  The same method applies to the other set up, but since it's enclosed it's much harder to see.

Take a look at the images in this post and you'll see a variation on the barrel on the lower lock - the only real difference is that the rectangular section is larger on the CA77 one.  The instructions I wrote in that post about how the lock is removed also apply to the 750 locks.

I've managed to remove a couple of locks without doing either - trust me, it was more luck than judgement and not something I'd recommend.  It only works with the lock mount shown in the first couple of photos (where the lock isn't entirely enclosed.  Basically the method I used involved sticking a screwdriver behind the frame section you can see in your second photo.  Look at the lock end, and you'll see one 'leg' longer than the other . . . I got the shorter leg to bend out just enough for the pin to pass by it by belting it the right way and then knocked it back into place once the lock was out.  But I've since found it's a high risk strategy and should be avoided if you don't want to risk snapping the mount.   

In the last of your images, you can read the lock number - looks to me like it's T3879.  If you haven't already, order one off eBay and while you're waiting for it to arrive, fill the lock with WD40 or some other penetrant - chances are it's frozen in place.

Not a textbook assembly, but these may help . . .

Looks like I have the wrong battery sticker but whatever, it's on the inner rear plastic mudguard.  Not a lot of other places to stick it.

Helmet holders are on the raised rear section joining the frame sides (the bit that supports the back end of the seat).

Sorry - can't work out how to embed images from Google Drive . . .

Doesn't look like it shows up on any of the K model microfiche drawings (although I'm sure I've seen them on K's). 

There's a sticker shown on the F model diagrams, but some of the parts lists no longer list the part number.  Since the battery design and routing isn't all that different to the K models, I think the sticker you're referring to is part #24 on this diagram.