learning how to learn

[JD]

The bike: 1979 R65 w/30K miles

The project: Purchased last fall, the bike seemed to run well. It wintered in a dry garage but was hard starting in the spring. Had it tuned at a local beemer shop  and it ran well all summer.

The problem: Now it's dead again, no crank/no start. My son rode it to class one night and on return it wouldn't start. He said the starter turned over for a second and then all dead, nothing.  Had it picked up and now it sits in our garage. The battery seems ok, tests at 12.65 v. The only thing that works is the daytime headlight. So, we lifted the seat, pulled the tank and that's where we're stuck at the moment.

I'm trying to learn, along with my son, how to go about diagnosing the problem but with a (on my part) serious mental deficit of understanding things electrical.  I'm wondering if some kind souls could suggest or help walk us through on how to learn what to do to figure this out. We have the Clymer manual and a multi meter.

Thanks so much for any help.

[montmil]

I'd be suspicious of the battery.

During the winter storage, was the battery kept on a tender? A float charger that cycles on when voltage drops to a specific level? How old is the battery? Wet cell or AGM?

Your VOM may show what appears to be adequate voltage but the battery may not have enough muscular amps to power the starter. Also, the charging system on our R65s does not begin providing adequate charge to the battery until around 3000 rpm. Urban driving, with multiple traffic stops and lower revs can quickly drain a battery no matter how new it may be.

Check battery cables. Clean off any corrosion. Confirm the ground cable is, well, grounded. Don't go all King Kong on tightening the cable where it attaches to the transmission. Steel bolt-aluminum threads-stripped. RuhRoh.

If you have a FLAPS -Friendly Local Auto Parts Store- nearby, take the battery to 'em and they can 'load test' it. You'll probably know what to do next. In the meantime, slap it on a charger. And remember to keep the revs up during urban assault riding.

Report back with what you discover.  [smiley=thumbsup.gif]

[JD]

Pretty sure I can eliminate a battery issue, have had it on the charger and it seems up to snuff.

[montmil]

Pretty sure I can eliminate a battery issue, have had it on the charger and it seems up to snuff.

Load tested? Wet cell or AGM? Age of battery?

[Barry]

If you don't want to take the battery for a load test then measure the voltage of the battery during a starting attempt. This simple test should narrow it down to battery or starting circuit.

If the battery voltage falls much below 10 volts and the starter doesn't turn the battery is knackered - you just did a crude load test.

If the voltage doesn't fall at all or very little then the starter is not attempting to draw current so there is a fault in the starting circuit. Starting relay will be the next thing to investigate.  Do you have a wiring diagram ?

[JD]

Thanks guys for the help so far. Yup, looking like the battery had me fooled. Took it to the local supplier and had it load tested, guy there said it was weak. Nice guy, offered to put it on their trickle charger overnight to make sure. We'll go back tomorrow and check it again but my hunch now is we'll be picking up a replacement. I'll let you know how it turns out. Thanks again.

Jim

[montmil]

...my hunch now is we'll be picking up a replacement. I'll let you know how it turns out. Thanks again.

Jim

AGM batteries are quite popular with Airhead owners. Check the General Announcements section for a good deal on a correct size AGM battery. R65 forum peeps get a discount. Be sure to ask for it.

[Bob_Roller]

Unless the bike is ridden at highway speeds, the Bosch charging system doesn't provide enough power to charge the battery .

City driving will drain the battery in about a week of riding, had this happen to me when I lived in Chicago .

Now I have highway speeds to work, 70 mph and no issues in the last 23 years in Phoenix, other than batteries die in 2-3 years due to heat !!!!!

[Barry]

My experience is not the same as Bob's.   I ride a short commute of just  under 4 miles to work and 4 miles back again. I wouldn't call it city driving. Even though the speed limit is mostly 30mph I keep up a brisk pace and there is only one set of traffic lights and that only on the way home.   With this type of use my hybrid Gel/AGM battery stays fully charged although the previous wet cell didn't and required a weekly top up charge.  That will have been down to the higher self discharge rate of a wet cell particularly when old.

Other than making sure all the connections are clean the only thing I've done to the charging system is to increase the voltage regulator set point to 14.5 volts cold 14.3 volts hot. This I consider essential to raise the charging voltage to what the battery manufacturer recommends.  With the lights off my gen light goes out at 1000 RPM and stays out.  

Even with a wet cell there will often be scope to increase charging voltage because German manufactures have in the past had a bit of a reputation of being too conservative with the voltage set point often setting it as low as 13.8 volts. That was reflected in my 1989 Mercedes 190e which was hopeless with a best of  13.8 volts cold falling off to 13.6 volts hot but I've been gratified to find they have upped their game on my 2009 C class which charges as a high as 14.6 volts and that's not with an AGM battery. Even wet cells of the modern no maintenance type can and should be charged a few tenths above 14 volts.  

[JD]

Thought I'd get back to say yup,it was the battery. Had the old one load tested and it was dead. Put in a new AGM and all seems well again. Thanks to all who responded.

[montmil]

Now that you have a spiffy new AGM battery, it's time to upgrade your voltage regulator to a solid-state unit that will maintain the AGM battery at a higher 14.2 voltage than the stock regulator allows.

Rick Jones at Motorrad Elektrik has a plug n' play unit that's perfect for the Airheads. Got 'em on my bikes.

http://www.motoelekt.com/charging.htm

[Semper Gumby]

+1 Rick.  Also get a Deltran or SnapOn trickle charger and keep the bike "pluged in" when it sits.  This will help keep the battery ready for action and make it last longer.