I have just one piece of advice to add to the above:
DO NOT jump on the kick starter or use any sort of tool (like a breaker bar) on it. The kicker is not designed to break loose a stuck engine and all you will do it ruin some of the gears inside or possibly break the kicker shaft - which is a fairly big job to repair.
Take out the spark plugs and put something like Marvel Mystery Oil (
there are lots of witches brew suggestions that people use - another is a mix of automatic tranny fluid and acetone) down each hole and let it sit for a few hours/day or so (and leave the plugs out throughout this entire operation).
Then I would recommend following Gary and Ratranger's suggestions and shift into a high gear (3-4-5) and then sit on the bike and simply jog it back and forth till you detect motion -
and/or - take off the round left side cover plate (the one that says
YAMAHA on it - held on by two JIS screws) and gently rotate the big nut back and forth to get the crankshaft moving a little.
Be patient - this may take a little while - but they nearly always break loose with a bit of effort.
Not to worry - it is likely that the piston rings are stuck with some gummed up oil and old gasoline or possibly a bit of rust but once it starts to turn, the engine should come back to life OK or possibly it may just just need a bit of hone and clean up with some new rings. As Raymondo says, these are simple machines and parts are readily available plus there is tons of help available on this forum including several step-by-step threads on how to do the top-end on an XS650. In my view, the best rebuild thread is by forum member Jim on getting his Miss September back in shape.
Here is the linky:
http://www.xs650.com/threads/jims-1980-sg-miss-september.50545/). Read that one over and when you are ready, follow Jim's steps through the top-end rebuild and when you are done, you will have an extremely nice bike to ride (plus it is a total chick magnet)!
QUESTION: it the bike complete (are the side covers and original handlebars with it)?
COMMENT: these older bikes are becoming a bit rare and that one looks good - so if you plan to chop it, please don't - until you have ridden it in stock condition. It is of course your motorcycle but I must tell you that most of us have found that the XS650 truly is a very nice bike to just boot around on and with a few simple modernizations (chiefly to the electrical system), they are reliable, safe and truly a blast to own and ride.
If you really want one that has been chopped, there are lots for sale on this forum or on Craig's List. Just search for "
For Sale: failed chopper project" - as many of them are either incomplete (
because the owners had more ambition than money and/or skill) or the owners find them so uncomfortable that they cannot be ridden more than a few miles without painful back injuries.
....and welcome to XS650.com from Canada's sunny southern coast in Windsor, Ontario!
Pete
PS - you will need to post A LOT more photos.