So I really don't need some sort of monster top end either. So I'm thinking that really wonderful wide torque band and smoothness of a 4-cylinder 4-stroke geared to let it pull like a mule between about 30 and 70 mph in the gears will be just the ticket.
I can't see how you'll be happy with a 550. While the engine is certainly smooth, you need to work the left foot to get torque, meaning it must be in the upper RPM band before throttle twist has much authority. The Harleys are all about throttle twist, in whatever gear you are in. The 550s need to be above 5000 RPM to get throttle twist thrill. If you are in the twisties you want to be above 5000 when 2/3 into the turn so you can accelerate out. To scoot you need to work than downshift routine. It is only going to haul ass when the red line is teased.
If you cafe it, that usually means exhaust changes and loud, scaring deer into your path and polluting the quiet countryside particularly if you keep the R's up to be in the power band.
The 550 ain't no torque motor. It's a horsepower motor and to get that horsepower, it needs to rev. And that means a lot of action with the left foot.
The 550 is totally wonderful in the turns as it handles superbly neutral in the stock set up. Much of that handling is destroyed by wide tires and other changes that occur along with gaining that "cafe look".
It is quite rare that a "race thoroughbred" is also a well mannered street machine. Race machines expect the operator to "work" them. IMO
If you are buying a bike to mod the crap out of. Please stay away from destroying pristine stockers. The basic bits you need to build a custom "whatever" are all present in a derelict/ignored example. This way, you are adding to the bike pool rather than subtracting a well kept example from the total population. (also IMO)
For trans and clutch reliability, stay away from the US model 500s.
The front forks were improved for the 74 CB550 and later.
If you want to avoid rocker shaft elongation wear, stick with the 77-78 models F or K.
If you are going to keep the stock air box, the 77-78 K couplers are quite difficult to replace.
The PD style carbs found on the 77-78K models, allow finer pilot circuit adjustments and are more precisely tuned/set up for, the stock exhaust and intake system. Some find the changes in internal carb set up to be more difficult with the PD carbs than the "sloppier" earlier style carbs (which, oddly, can also be found on the 77 CB550 F model.) Any induction system changes will require internal carb set up changes to both carb styles. And, if you change the exhaust on a PD carb equipped bike, be prepared for carb set changes for that, too.
That's all, off the top of my head.
Cheers,
