A list of the XS650 Yamaha's foibles.

As far as what to watch for, these are very simple and robust bikes with the components in full view, and it is difficult to go wrong. The chronic issues that plague XS650's are very minimal and easily repaired. Besides the things one should look for in any older motorcycle, such as a bent frame, bent forks, worn sprockets and chain, etc, particular to the XS650 is the following:

(1) Failed Alternator rotor. If the headlight does not brighten significantly when you rev from idle to 3000 rpm then 90% it is the rotor that has failed. $175 for a rotor, but you need the special $17 puller to change it out.

(2) Worn alternator brushes, same symptoms as above; about $25 to replace if you seek factory replacements. But you can go to a hardware store and buy brushes that are close for a couple of bucks, and sand them to fit.

(3) Worn swing arm bushings. $30 for bronze replacements, but can be very difficult to change. With the bike on the center stand there must be no play whatsoever in the swing arm when trying to shake the back of the rear wheel side to side. This is a handling and safety issue and these MUST be replaced if any wear exists.

(4) Leaking clutch rod seal; $16 (this $8 for the first seal which you will destroy trying to install, and $8 for the second seal which you will install successfully after having learned how to do it after seeking the advice of someone who has already done it successfully. Buy two immediately)

(5) Bent forks, due to inherently weak tubes. They are easy to straighten by pushing the wheel against the wall, however, be sure to loosen all clamp bolts and the axle bolt before doing this.

(6) Worn #4 gear for the electric start, probably about $40 but this is a guess. If the bike makes horrendous grinding noises when starting on the electric starter, the gear is failing. If the bike makes the same horrendous noises without starting at all then the gear has failed. If the bike doesn't make horrendous grinding noises when starting, it will sooner or later. But these bikes start on the first kick anyway.

(7) Torn metal mesh in sump oil strainer. This is not visually verifiable, but it is torn, trust me. It costs $25 for a better after-market replacement.

(8) Rotten foam in airbox filters. They are about $40 at a breaker if you can find them, and who knows how much at Yamarobber. Emgo filter pods, with the necessary jets, breather filter and inlet extensions will set you back about $60 plus two months of your life as you struggle to get them to run properly. You should spend about $50 more and buy K& N filters, and save some of that two months for riding.

(9) Lost horn and starter buttons; $6 each

(10) Disintegrated fuse box: $10 for suitable replacement at Radio Shack.

(11) Broken center stand tang. This bike is hard to lever onto the center stand, unless you know the technique. This results in the center stand tang, whereon one places their foot when heaving the bike onto the center stand, to crack at the base. This can be welded, while on the bike, and a little gusset added to prevent re-occurrence. Be sure the gusset is positioned so it is flat and horizontal when the center stand is folded up, if it is vertical when in the folded position there is a good chance it will interfere with after-market mufflers and put a ding in them.

False alarms:

Don't be put off by things like non-operating flashers, the XS650 flasher system will not work unless you have a fully charged battery, and very often they have the wrong wattage bulbs installed, they take a special bulb. The correct bulb is an 1156. Or if it doesn't show a number it may show 12V27W.  The card may even say 12 Volts 2 Amps or even possibly 2.25 amps.  Some bulbs show nothing once you take them off the package.  But find a bulb 1156 and you will be OK.  They can be hard to find, you may have to order them, so buy a couple of spares when you do.  They also come in LED form, I have no idea if these work and I would doubt that they do. Likewise difficult shifting and inability to find neutral, this is almost always just a case of clutch adjustment, made difficult by the too short stock clutch cable

I would confidently buy a non-runner, as long as I could kick the engine over freely without any odd mechanical noises and as long as there was decent compression felt by keeping one's thumb over the spark plug hole while kicking it. If you want to be anal, and insist on using a compression gauge instead of your thumb, then the lowest cylinder at 115 psi with the higher within 10 psi of this will give you a bike that will run just OK, 130 psi per cylinder is great, and
150 psi is superb.

These bikes are the best value you can buy with respect to reliability, ease of buying parts in the rare event you need any, and that is usually only after you drop the bike, riding fun, and pure good looks. They are much better bikes in every respect than the Triumph Bonnevilles and Norton Commandos that sell for four times the price and more.