77 R100/7 suddenly, instrument lights out and not starting

[tourists]

Back home for a few days and I have my dad’s 77 R100/7 here that I’m trying to get started. It was running fine a few weeks ago then suddenly not.

Key on, new battery, in neutral: Only the orange turn signal indicator light is on and no other instrument lights. No response from pushing the starter button with or without clutch lever pulled. Initial searches had me jumping neutral and clutch switches but no luck.

The instrument lights being out is making me wonder: would a dead starter relay affect the all those lights in the cluster? This is my first time with electrical challenges so I’d love some thoughts on where to go.

 

[jad01]

The instrument lights being out is making me wonder: would a dead starter relay affect the all those lights in the cluster? This is my first time with electrical challenges so I’d love some thoughts on where to go.

Yes, if the starter relay is not making good contact at the terminals, it can cause the lights on the instrument panel to go dead, in addition to preventing the bike from starting. The relay may be bad, but it seems more likely that the contacts are dirty/corroded. The location of the relay under the tank makes it prone to corrosion where it plugs into the wiring harness. First thing I'd do is pull the relay and plug it back in two or three times to ensure good contact. If the male blades on the relay are green/dirty/corroded, you might take a little fine sandpaper and clean them. Good contact cleaner sprayed in the plug/female sockets and then plugging the relay in and pulling it out several times will likely help clean those out as well. New relays are cheap if it is in fact bad- check out www.motoelekt.com.

It would also be a good idea to check the ground at the battery/engine case, and ensure that the battery is good/charged before springing for any new parts. If the ground cable is at all questionable, I'd recommend replacing it (again, an inexpensive part). If the cable grounds to the engine case where the speedometer cable engages the transmission, be careful not to over-tighten that bolt... it is hollow and the threads on the case are delicate.

 

[willhawks]

Jim's advice is spot on

I owned a 78 /7 myself. at some point in my learning curve my guru (The late/great Keith Patchett) told me whenever assembling electrics after a cleaning to add dielectric grease as well. While I can't prove cause and effect, it seemed that I had less electric problems after that. FWIW

Best,

Will

 

[20774]

And just for the record and future searches, his first name was spelled weird - Kieth:

https://books.google.com/books?id=Q...qSCh2C9g0X#v=onepage&q=kieth patchett&f=false

 

[SCBuckeye]

Had mine conk out similarly - first just a split second while going about 45 MPH, but came back on - then happened again, and then while just getting ready for pulling onto a small street off a state street, it went cold. I was just fiddling, and stuck my fingers under the front left side of tank, and viola, lights came on, and bike started. I took off tank, and cleaned all connections of relays (be careful, some connections there are hot all the time!) and then I took a piece of thin plastic (from an old plastic milk jug) and "shielded" the area from water and weather that might blow in from the front.

Worked! Never had the problem again!

 

[tourists]

Looks to be a relay problem, cleaned the terminals and no change so we cracked open the relay and found a massive amount of corrosion. We were able to hot wire it to crank so at least the problem is isolated a bit. Now it's new relays and fixing the leak in the brake fluid reservoir that seems to be causing that corrosion. Thanks again for the info here!

 

[tourists]

And just for the record and future searches, his first name was spelled weird - Kieth:

https://books.google.com/books?id=Q...qSCh2C9g0X#v=onepage&q=kieth patchett&f=false

WOW... These scans of American Motorcyclist magazine. There goes my weekend

 

[dennisdarrow]

You do know of course, that the brake master cylinder there under the tank, the culprit for not only this problem but paint, engine case tarnish, and umpteen other things, is easily rebuilt via a kit or several folks who specialize in these repairs...... God bless.....Dennis