[Unkle Krusty]

Wot Slum said.
The CB550 was a good bike with a good engine. The CB650 had some top end issues. The CB750 was also reliable.
The seventies bikes did not handle as well as the eighties bikes, but are acceptable. The early eighties Suzukis probably handled the best.

It is amazing how much better an old bike will run, with new electrical wyre and connections. My XS1100 Yamaha improved the miles per gallon by a large amount, after fixing a bad connection to the coils. Even a corroded wyre to the tail light, creates resistance and takes away watts from other parts.

UK

 

[Unkle Krusty]

Engine rebuilds are for experienced mechanics, and not many of them are capable of doing a good job.
Better to spend that time riding, and buy a low mileage engine. I have a spare XS1100 engine with 25,000 miles on it. Paid $100 for it, which included the frame and rear end.
I also have a spare engine for my XS400.

Wyre for boats is a bit more money, but is a lot better quality. Simply a matter of replacing what is already there. The biggest issue is whether to use the original corroded connectors, or replace them. Hondas have colour coded wyres. Blue, brown, black, yellow, red and white mostly.

UK

 

[Unkle Krusty]

What exactly is it that makes a rebuild difficult if there are step by step videos available for that exact engine?

You need to decide how many angles to have on the valve seats, and which shop will follow your instructions.
You need to know how to plaster gauge new crank bearings, if you can find crank bearings, and someone to grind the crank if it needs it. You need to be able to measure the crank accurately. Same goes with the pistons and bore. How to end gap rings and what piston clearance to run. You need to know how to put a degree wheel on the crank and set it. Then you need to know how to accurately time the camshaft.

By now you will be down a lot of $$$$ and wasted about six months with no end in site. So you will also need another bike to ride while the fixit bike is being fixed.
You will most likely need to change the steering head bearings, the wheel bearings, the swing arm bearings, the fork seals, the brake pistons and pads, the sprockets and chains and a bunch of things I have not thought of.

You will need to change your own tyres and get them balanced. The carbs will be plugged and dirty / rusty inside. The gas tank may need a lining, the pet cocks will leak, the head light will fail, and finding pipes will cost a lot.

There is a lot of good info on the internet. There is also a lot of misleading info on the internet. I have not checked any sites about rebuilding engines.
As I said above, I have a near new low mileage 1100cc engine for $100.

UK

 

[Unkle Krusty]

There was a time when I knew just about everyone who worked in a bike shop from Vancouver BC, to Portland OR. Plus some guys who worked inland. Only one out of the entire bunch was good at rebuilding Honda engines. He got hired by Canadian Honda in the late seventies and is still there. He also went with me to the bike races for a few years.

I also knew nearly all the guys that raced on the three North West tracks, Westwood in BC, SIR ( Kent ) in SW Seattle, and PIR in Portland. Only a handful of those guys could rebuild a two stroke crank. Engine rebuilding is a specialized business, and completely non doable by a rookie, IMO.
Back in the day there were more machine shops that could do decent work. On the plus side, there are internal parts available for many engines. On the downside, a gasket set might cost more than a decent engine.

My price for a complete XS1100 as a spares bike, would top out at $500.

UK

 

[Unkle Krusty]

I used a CB750 front brake master cylinder on one of my race bikes and tortured it. Worked like a charm.
As above, the guidance system was the biggest problem. The stroker kids rode the 500 and 50 Kawasakis to death, and the CB750 and later the XS1100 Yamaha and the 1100 Suzuki. That is why so many are in the dead bike yards. Low mileage engines sitting in bent frames.
All the Honda engines and gearboxes were very reliable, more so than any others from the seventies. That includes BMW.

UK

 

[Unkle Krusty]

Back in the day when I was selling bikes and taking trades, I would spend time checking the alignment of the front forks, bars, swing arm and so on. Then check for scratches on the levers, all four, and the engine casings. I wanted to figure out if the bike had been dropped and how often, and how severely.

That plus the miles and how it ran. And if the brakes worked. The cables and tyres could also tell stories. Most bikes had spoked wheels back then. Broken and missing spokes, and wobbly wheels were not uncommon.
I left that company in 79 and they hired an incompetent friend. They went bust in 82 with too many over priced trades.

UK