My 550xs hasnt been started
Three possible causes for your problem immediately come to mind: (1) starter; (2) engine; and (3) electrical system.
1. Starter. The oil seals in some Yamaha starters have a nasty habit of hardening and letting oil seep into the starter. That oil acts as an insulator and prevents your starter for working properly. In particular, the "brushes," which are a high-wear item to begin with, are positioned in a way that they can easily get saturated with oil, at which point they no longer conduct electricity. Thus, electricity will flow to the starter, but it's just locked up in place. Replacement starter brush assemblies are generally available through Yamaha parts suppliers; Yamaha tended to use the same starter in multiple bikes. While everything is apart, it's also a good time to replace the oil seal around the starter shaft. Yamaha does *not* sell these, but you can match the part by its size at a bearing and seal shop. It will only cost a few dollars, and it'll make a world of difference for the longevity of your starter.
2. Engine. Before trying to start your motorcycle, did you double-check to make sure that your engine was turning over? Engines that have been stored for long periods of time can have the pistons rust in their cylinders. Or, if you didn't drain the tank, the crankcase can overfill with gasoline mixed with oil, causing hydraulic lock on the bottom end (happened to me once with an XS650; a quick oil drain and fill solved that problem). Pull the spark plugs and squirt a bit of lightweight oil into each cylinder. Then, using the kick starter (this is an old 1970s XS550, not a more recent XJ550, right?), slowly turn over the engine. The pistons will push the oil up and down, coating the cylinder walls. If you don't have a working kick starter, put the bike on its center stand and put the bike into 3rd or 4th gear. Then, rotating the rear wheel should turn over the engine.
3. Electrical System. In my experience, vintage Yamaha electrical systems have proven to be more unreliable than their Honda counterparts. Sometimes, wires can lose their insulation and short out. Much more commonly, terminals and connectors tarnish or corrode and fail to let full amperage through. Connect a test meter to the positive terminal of your starter when it's installed in your bike, grounding the negative lead to the frame or the negative terminal of the battery. When you press the starter button, what voltage do you see displayed on the meter? You should see the full battery charge--about 12.6 volts for a fully-charged motorcycle battery--but you might see noticeably less due to electrical gremlins. If this is the case, start by cleaning all the visible terminals you can see--generally speaking, the starter terminal and starter relay terminals. If you don't see any voltage at all when you press the starter button, your starter relay may have gone bad.
Good luck!
