Well, the other day I decided to take my '87 K100RS in to work.  Started up just fine (battery was hooked up to the trickle charger over night), took off down the road, down shifted coming up to a stop sign and the bike stalled.  I went to restart it and the starter kept kicking but no ignition.  I was able to push start it and get it back to the house. I let the bike run for a while, cut it off and tried to restart it but was met with the same issue.  I hooked up the charger, went to work, and 9 hours later the bike started right up.  When I cut it off and went to restart it, same problem.  I am thinking it may be the alternator.  Anyone have experience with this?

Many thanks! 

Charge the battery, put a voltmeter across it and take a reading. Start the bike, let it tick over, take a voltage reading. Rev it to 2000+rpm and take a reading.
The results will tell you exactly what the problem is.

Does the engine spin over and not start or does it just not turn over at all?

If your alternator isn't working then the charge light should come on in your instrument cluster.

Measuring the voltage of your battery tells you very little.  

Take your battery to an auto parts store and ask them to load test it.  They will do it for free. (It helps them sell batteries.)

good question rick ....not enough info so far, 

thinking dirty - bad starter brushes already

"Measuring the voltage of your battery tells you very little."

You are only measuring the voltage of the battery when the engine is not running. When running you are measuring the voltage of the bikes electrical system as produced (or not) by the alternator.

If the starter is turning the engine over then it likely isn't an alternator issue.

The engine is not spinning over.  The starter engages, but not the engine.  Come to think of it, the charging light was not on while it was running.  My question is when it stalled out, why wouldn't it start again?  At some point this week I'll bring the battery down to the shop and have them look at it.  Not like I'm going to be on the road anytime soon...too much snow and ice

Thanks all!

The charging light should go out once you have sufficient revs to have the alternator putting out. If the alternator does not have sufficient output to excite the charging circuitry then the light will stay on.

The starter engages, but not the engine

Do you mean that the starter engages, and tries to turn the engine over, but can't, or that it engages and spins, but the engine doesn't?

Mike

When you rev it and the headlight brightens that tells you that the alternator is working.

Save money and weight buying a battery: http://classickbikes.com/ckb.tech/0.ckb.tech.files/batts/batteries.htm

gellermpd wrote:... Went to restart and nothing but starter turning over...

Hi there, so the starter is turning over the engine but there is no ignition. If that is the case I would not think the battery is at fault, usually a faulty battery has no strength to turn over the engine. Or I´m missing something?
Best regards
JAP

As Duck said earlier get the battery load tested and DON'T try to start it again till the battery is known to be good because you have a high risk of welding the starter relay contacts together, costing you a relay as well as a battery.

RicK G wrote:As Duck said earlier get the battery load tested and DON'T try to start it again till the battery is known to be good because you have a high risk of welding the starter relay contacts together, costing you a relay as well as a battery.

+1 on that one.

Signed,
The Voice of Experience  

Thank you all!  I am going to pick up a new battery sometime this week.  I will update then.

Again, many thanks!

Don't just go out and spend money on a new battery. A load test will tell you whether the current ( ) one is still good for service.

Mike

Ok.  Old battery was no good.  Replaced it yesterday and the bike cranked right up without any issues.  Ran it for 20 minutes and shut it down.  Went to restart, no issues.  Took it in to work this morning without any issues. Before the ride home it fired right up.

Soooo...that being stated it was the battery.

Thank you all for the input.  Now, I am more knowledgeable on this subject matter.

Again, many thanks!

I love a happy ending!!!

klamityboy wrote:I love a happy ending!!!

Thai massage? 

Oh, very happy endings indeed!! ;-)

Not sure where you guys are buying your batteries, but thai massage is definitely not offered at my battery shop!!!  Or were you just speaking about "recharging your batteries"!!! 

Not sure my batteries would keep a charge at a thai massage parlor...