The R65 doesn't have a distributor, your bike if it hasn't been altered or modified by a previous owner, will have a contact point type ignition system .
The 'bean can' is located under the alternator inside the front cover .
The airhead bikes have what is called a 'wasted spark' ignition system, both sparkplugs fire at the same time, so you don't need a distributor .
How many kilometers has the bike been ridden ?
Normally the timing chain is good for alot of useage .
Easiest way to check the chain for being worn, is to use a strobe type timing gun, if the image you see in the timing hole is blurred when the light is working that is usually a good indication of chain wear .
If you are not familiar with an airhead BMW engine, they make a few unusual noises compared to say an Asian bike .
If your mechanic took the cylinders off and found nothing wrong, there probably isn't anything wrong with the engine .
The transmission is another source of odd noises with the engine running and in neutral .
