If it isn't Honda, it's going to be tough getting OEM parts. CycleMax is a dealer that is in Pennsylvania that did very well finding my dad some parts for his vintage Honda. You might give them a call. I'm not sure how their resources are for old Yamaha.
Check out the used parts too-
I can't think of the others off the top of my head.
So yeah, I don't want to discourage you- old bikes are lots of fun, but parts are a bitch pretty much all the way, and not cheap either.
Basic parts are still going to be easy to find, simply because Yamaha didn't make them to begin with. Things like 2 stroke oil (only use oil for oil-injected bikes), spark plugs, chain, sprocket, etc are easy to find. Sometimes cables/control assemblies can be retrofitted from other bikes. For example I think the throttle cable from a Honda XR-80 can be interchanged with the throttle cable on a '71 SL 125 (if memory serves). In many cases reed valves, pison rings, etc are also not hard to find.
Hardest parts to find for anything old and Japanese are things like gas tanks, side panels, and fenders. If you can repaint or refinish what you have, it can men thousands of dollars and hours upon hours of seraching for the right parts.
In many (not all) cases, you can still get aftermarket rebuilt parts. Fork seals, piston rings and the like can be easily found in most cases.
On the other hand, if you need a new cylinder head or bottem-end rebuild, you may be up a creek. These parts are becomming hard to find.
Hope this answers some of your issues. Good luck whatever you decide to do. Old bikes are a blast, BUT (that big butt there now)
The brakes are gonna suck if you're accustomed to riding a new bike
While the old timers will tell you how fast they are, they're not- plenty fast to kill youreself, but not fast compared to most other dual sports/dirt bikes today
You'll want new tires, especially if they are trials tires or knobbies. Riding on 20-30 year old tires isn't a very smart idea unless you aren't going to ride much off the road. You're just asking for trouble if you do
There is no suspension on an old bike. Sure, they look like they have forks and shocks, but they don't. All 6 inches of front travel and 4 inches of rear travel are taken by any rough trail.
Keep a spare or 2 spark plugs with you- those old 360s gobbled plugs like none other, or so I'm told anyway. My dad owned one, I personally have never ridden one. I have had the opertunity to ride plenty of other vintage hardware, and it is totally cool. I love the feel, the look, and everything. I didn't grow up around these bikes, but there is something undeniably cool about the crackle and blue smoke from a two-stroke. I don't own any vintage hardware, but I'm sort of looking for a Kawasaki KE250, or 350 BigHorn enduro. I own a '01 KE 100, which is a cute, nostalgic bike. It's the closes thing I have to vintage, with drum brakes, tiny suspension, 2 stroke, oil injected etc etc. Love it to death. I've put over 1,000 miles on it since I moved to AZ a year ago, which believe me is a long way with the handlebars buzzing... [img]/ubbthreads/images/graemlins/laugh.gif[/img]
Good luck whatever you decide. [img]/ubbthreads/images/graemlins/smile.gif[/img]