Boxerworks.com

Hi,

I am recommissioning my 81 R100CS after a couple of years sitting in the garage. The old battery was shot so replaced with a new 20amp AGM one. On trying to start the bike the starter motor just goes 'clunk' and refused to turn the engine over. In case the engine had seized I removed the plugs and squirted WD40 down the plug holes. Pushing the bike in gear I was able to turn the engine. But still no joy with the starter. Is this a case of a stuck starter or what. Any ideas please as to cause and solution

Carefully check that your main battery cables are good from end to end. If both cables are solid, try boosting it with your car.
Sounds like a bad starter or a dud 'new' battery.

About the same thing happened on my '84 RS...new battery and the starter wouldn't go. Charge the (new) battery and it was good to go. That was a new one on me.

Hi all, will take the starter out and check it then report back

millerboy998 wrote: ↑Wed Apr 09, 2025 2:57 pm Hi all, will take the starter out and check it then report back

Why take the starter out? All tests can be done with it in place.
First (and most basic) test is trying it with 'known good' battery and booster cables.
Why open a can of worms if it's not necessary?