This is a compendium of the areas of the vintage Honda that need the most attention when putting it back into service. Square these things away first. These needs will also be found to be the most critical in terms of regular, systematic maintenance. In both instances, take these suggestions to heart. They're born of a lifetime of career-level training, experience and familiarity with these bikes.

1970s SOHC fours
Unquestionably, the single-cam Honda fours of the 1970s (i.e., 350/400 four, 500/550 four, and the venerable 750 single-cam four), are the most vulnerable in their ignition systems. The ignition system counts for more, contributes more, to how well the engine runs, than any other thing. Yes, (much) more than the carburetors, more than the air filter, more than the kind of fuel you use, and even more than the choice of standard or iridium spark plugs (which, though part of the ignition system just won't make up for a lack of maintenance elsewhere). The owner of one of these bikes must learn expertise in tuning the ignition or find an expert. Both can be difficult. But there is no other way.

70s/80s DOHC fours
Here, on this range of Hondas popularized in 750, 900, 1000 and 1100 iterations, the problem is valve seal. While all Hondas up to the mid 1980s suffer from quickly-wearing soft valves, the first-gen DOHCs are infamous for A) the valves receding at an unbelievable rate, and B) the valve seats in the head squirming out of true with the valves due to heat. The two together result in depressingly low cylinder compression. So this then is "job one" when fettling one of these machines. Where resources are spent first. Any other approach is a waste of time.

The six-cylinder CBX1000
Being a sort of kissing cousin of the aforementioned DOHC bikes, Honda's superlative CBX bears the same valve and valve seat DNA. And actually the problem is worse in the CBX. The CBX is much hotter running and the valve seats shift so much that when doing a valve job you can actually track the heat path as you service one combustion chamber then the next. The inner cylinders' valve seats are worse than the outer cylinders'. I have written about how to approach valve seat work on this model. It's a challenge. Without the most sophisticated tools, it's nearly impossible to do right.

Honda GL1000
Once again, here's a bike whose ignition system presents very significant hurdles to getting this engine to work properly. So much so that even among seasoned Honda mechanics very few know what to do. If the SOHC four ignition is way beyond most people's capability, this ignition is ten times worse. The carburetors present their challenges too, being unlike anything most mechanics will ever have encountered, it's not unusual for at least one of the two camshafts to be mistimed, and cylinder wear is usually excessive. But proper tuning of this machine goes way beyond even these demands. Successful tuning of the GL1000 requires you know many intimate things about this ignition system, secrets that only decades of studious effort reveals. It is not at all intuitive. And substituting an aftermarket electronic ignition, with their quirks and unreliability, relieves only a part of the pain. Don't even dream you can make this bike run right without this special knowledge.

Honda GL1100 and GL1200
The ignition system is seldom a problem on these models, if you discount the 1100's tendancy to over-advance. The carbs too are pretty reliable. The GL1100's main problem is rusty fuel tanks, a fault it shares with the GL1000. The GL1200 is perhaps the least troublesome of all the four-cylinder Wings, so the focus when rehabilitating one is going to be the carburetors, which like any vintage machine will be resined-up and are likely to have been badly serviced in the past.

Honda GL1500
Honda's first six-cylinder Gold Wing boasts just two carburetors, which are well-designed and very easy to service. The ignition system is happily troublefree. The problem you will find on this model is all of the wires and vacuum hoses that support this engine. Confirm they are intact and properly connected before you do anything else.

60s/70s 350, 360 and 450 twins
The ignition systems on the 350 and 450 can frustrate, for sure. More crude than that on the GL1000, they baffle many. And though the 360 carbs are fine, the 350 and 450 carburetors are troublesome. The 350 came with more than a half dozen different carburetors, each with its own code number. The 450 was produced with slightly fewer carb choices, but it made up for it by shipping with a mind-boggling range of main jet sizes. However, given all of that, the real downfall of these bikes is lubrication. With so little oil capacity people typically run these machines out of oil, particularly when they're run at high speed. Add to this the neglect the engines' centrifugal oil filters receive and you have the number one issue with these Hondas and the thing that must be addressed first. They all exhibit lubrication related issues.

First-gen Honda V4s
The 1982 through 1985 VF models are poster boys of idiosyncrasy. Peculiar. Unique. Mechanically beautiful. But they're just machines after all and they respond well to knowledgeable service. However, the people who have been in there before you will have timed the camshafts wrong. The symptom will be good running everywhere but at idle. You'll never get it to idle reliably. Honda was indecisive about the correct timing method, to the point that felt pen wizardry was encouraged in factory training school. A lot could be said about these bikes. If I had one in my shop today I would make sure I could find replacements for the short-lived cam chain tensioners, and that someone hasn't broken the carburetors removing or installing them. This is so common virtually all the ones on ebay are damaged. The rear wheel splines are rare now so if a drive shaft model I would also confirm that situation before committing to the project as well. Go after the biggest hurdles first, starting with the cam timing.

These then are the trouble spots of Honda's popular vintage motorcycles, the things you'd be wise to give attention to first so as to avoid getting too deep into a project before you find out it isn't worth it. Of course, the "worth" question is personal and it's up to you do decide that. But this list should help you approach minor restoration intelligently.