There is also
http://www.cmsnl.com/honda_model8286/You may want to contact the vendors too. They might have the parts you are looking for, but they may not have posted on their web site all about early 70's bikes !
What kind of part are you looking for ? Have you done a compression test on all four cylinders ? What kind of problem did you identify ? Has the engine ever been rebuilt ? What total is on the odometer ?
If I'm not mistaken, you are talking about a bike such as this one
http://www.cyclechaos.com/wiki/Honda_CB500Finding new parts will be quite of a challenge considering it is a rare bird, out of production for over 37 years !
Considering the difficulty of finding critical common parts that will eventually require replacement (ignition, gaskets, oil seals, chains and sprockets, all rubber parts) I don't think planning to ride this bike regularly will be an economical experience. Any engine part that fail may be a death sentence. This bike is made to fly ! but you are likely to burn its wings pretty quickly if the engine has not been already rebuilt.
If it is in near pristine condition, a collector may be interested to buy it to restore, otherwise, it is a very risky project for an everyday bike.
I question your will to ride this as a first bike too. This bike is VERY powerfull (50HP) and the engine weight configuration makes it quite heavy to handle in slow traffic. I'm not sure it is going to be very forgiving for a beginner.
Mine is a Honda twin cylinder from 1980. Despite the fact I just had the engine head, cylinders and piston rings rebuilt to specs, I'm considering buying another one just for a complete spare engine and critical parts. Mine is a very common model and there are still good spare engines to find. I doubt you can do the same, spare bikes and old new parts are long gone for such a rare bird.
In short, because this bike is on the countdown for running out of available essential parts. It is a better candidate for a collector than to be used everyday as a first bike.
