Dear BBQ: I had a similar problem with my '76 C model and while your bike is later with a more complex electrical system - I'm pretty sure that it still has a Starter Safety Relay. I just posted a test and repair procedure for this relay in another thread and it might help you out so I am going to insert it below. Good luck!
Pete
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Hi All: Well, its now been just under two weeks and the starter has not yet failed to crank the bike, so...it does appear that the Starter Safety Relay was the problem. In conclusion, if your starter button makes the oil pressure light come on - BUT - it doesn't commence any action from the starter motor - AND - you have a good battery and good ground connection on the handlebars, try the following little 15 minute repair job:
- remove RH side cover and the two large JIS (looks like Philips) screws which attach the Starter Safety Relay (SSR) to the frame of the bike;
- remove the electrical connectors so that you can take the SSR to the workbench;
- remove the very small JIS screws that secure the relay cover to the base (these little guys are really small - don't drop them!);
- GENTLY clean everything you see inside the relay cover with electrical contact cleaner and a toothbrush (including passing a business card between the two relay contacts to clean off any crud in there);
- reassemble and see if things work better.
Once again, I would
not eliminate the SSR, as others may suggest. The relay prevents the starter from being accidentally engaged while the engine is running and so it protects the complex, expensive and difficult to repair starter gears from being ground to a pulp. The relay is a simple device and it should be reliable - but after 40-odd years, it may simply need to be cleaned - mine sure did. Also, you can check the handlebar ground connection by simply checking to see if the horn works. If you get a good loud "beep" - you've got a good handlebar ground.
NOTE: this Starter Safety Relay problem is
not related to the well-known XS650 Bendix drive gear issue - if you've got that problem and you hear a horrible grinding sound when you hit the button, you will need to do an entirely different repair involving removing the RH engine case (clutch cover) and replacing the final drive gear and spring clip. There is tons of info and several videos on how to do that job.
Pete
