'78 R100/7 electric start problem

[almostblue]

All,
Over the past month, my starter has been turning gradually slower. Today it barely worked at all. I almost was stranded when I turned off the engine at a long stop light. I had to push start. Now the thing just makes some clicking sounds and the bike won't start.

I'm wondering if i need a new starter or whether maybe my battery is going bad. The lights all work. As an aside, I've noticed that my tail light flickers when i touch the wire. Could a short in that wire be messing with the starting system?

Anyone want to weigh in on this?

Thanks,

Paul

[20774]

Could be the starter needs a rebuild, but I'd look into the easy stuff first.

- What's the output of your charging system at around 3K RPM, measured at the battery terminals? Should be 13.5v...better if it was higher. Maybe your battery is not being fully charged. You could try a battery minder to keep the battery topped off...

- How do you ride the bike? Short trips around town or do you have a chance to keep up the revs for 30-60 minutes at a time? Short trips don't allow the battery to be recharged after the starter has pulled it down.

- How old is the battery?

- What does your digital voltmeter shows as the voltage across the battery terminals when you hit the starter? If you see 10.5 or so, that's OK...anything lower, and you might have a weak cell.

- Have you cleaned the starter relay terminals? It's a small black cube under the tank on the left side. Pull the relay out and replug once or twice...look for corrosion on the terminals...might try some cleaning lubricant on the terminals.

- Are your battery cables OK? Is there any swelling under the insulation that might indicate corrosion is reducing the amount of current that the cables can carry?

I'd get the wire fixed, but I don't think it's a big part of your starting problem.

[almostblue]

kurt,

thanks. i usually ride the bike at least once a week for at least an hour at a time, often much longer, almost always hitting freeway speeds. if anything, i would think my routine should be helping to maintain battery charge.

i'll try your test/suggestions, though.

if the starter needs rebuilding, about how much do you think it will set me back?

p.

[20774]

Paul -

Not sure about the cost on rebuilding starters... From what I've heard, they're not "rocket science", so with information out there on the web, you might be able to revive it yourself. Most likely you have a Bosch starter, and that's pretty standard for most places...being out of a BMW motorcycle really doesn't present a problem. I believe I've heard maybe $50 on the low end to around $100? Look for a small shop that specializes in starters...I found one here in town and will keep them in mind if it comes to that. I think someone like Rick at Motorrad Electrik can rebuild them as well.

But I'd go through the easier steps before you consider rebuilding the starter. Another thing to consider is going under the starter cover and checking all of the connections up at the starter. Sometimes corrosion can build there and reduce the amount of current getting to the solenoid and starter.

Good luck...

[almostblue]

by the way, where is the starter?

[20774]

Upper forward part of the engine, on top of the block...

http://www.realoem.com/bmw/showparts.do?model=0333&mospid=47881&btnr=11_1726&hg=11&fg=10

See the cavity on the top...the starter basically sits in this cavity. There's a vertical hole just to the left of the stud #7...this is the hole where the engine breather valve goes in.

There's actually a cover that goes over all of this...you'll see two allen bolts on either side that come off. The cover might be stuck but use of a rubber mallet, etc., can jar it loose.

[Polarbear]

Jump it to another battery, USING good caution to avoid grounding to the frame. The battery is in a tight spot so get some help and jump a good battery to it and see if the starter is working fine. Thats it! If the starter jumps to life, go elsewhere and look for the problem, like the alternator, battery, cables, etcetc. Good advice above, btw:). I'm a R100/7 onwer too, since new:)Clovis,CA. Yes, use your car battery, but take "heed" the advice, to "not ground it" at the bikes frame. Its much easier to get help and have someone just touch the cables to the "proper posts" on the m/c end, to avoid the nasty grounding/light show that will occur if impatient:(. Good luck, Randy13233:D :wave

[almostblue]

polarbear,
good advice. i was thinking the same thing but was unsure if i could use a car battery to do it.

thanks,

paul

[almostblue]

how do you get the battery out of an r100/7? what's the procedure?

[20774]

Drink plenty of your favorite beverage and send the kids away for the afternoon!!

Well, not that drastic...depends on the size of the battery. Some like to come forward, but you have to removed the air cleaner assembly. For me, I go out the top and towards the back. You'll need to remove the bolts that hold the top part of the battery tray. There are also some bolts underneath the battery tray that tie the tray to some rubber bumpers. I think you only need to loosen these a bit. After that, you should be able to tilt the entire battery/tray towards the rear fender. Then you can maneuver the battery up and out. There may be some clearance issues with one of the bolts that hold the subframe on. I take that off so I can spread the frame a bit. Then it will slide out.

I've used two batteries over the past 10-12 years, a Yuasa and a Mareg. They're both "full size" and completely fill the battery tray. There are batteries out there (Panasonic, Odyssey, etc.) that might be smaller and make the job a little easier. I prefer the lead-acid batteries and have had good luck with Yuasa's over the years. I'm trying the Mareg (from BMW) for the first time. I'll probably go back to the Yuasa when this one fizzles out.

[almostblue]

thanks again, kurt. i'm going to try to charge the battery before attempting what looks and sounds like an ordeal to remove and replace it. i noticed the battery was low on acid, so i added water and put it on a 2 amp charge.

the starter works fine on the charger, so i've ruled out other possibilities for the moment. i suppose i may end up replacing the battery, but i'm going to trying charging my old bmw-brand battery first. a new battery costs $109 at the dealer.

[skiteach]

I've been using NAPA garden tractor batteries. I get the most cold crank amps, that the local store stocks (current is 275 cca). They last a couple of years and cost less than $50. Are the other batteries that much longer lived?

[20774]

I tend to get about 5 years out of the Yuasa batteries...they run about $100. Let's see...tractor battery for $50 lasts a couple of years; fancy Yuasa, double the cost and lasts double the time. Sounds like a flip of the coin to me!!

[skiteach]

My/5 had a Yuasa, when I bought it in '76. It was the size of the one that had been in my Honda 360. Needless to say- it would barely start the BMW. Haven't tried any other batteries and was wondering.

[20774]

Hmmm...I don't think a battery sized for a Honda 350 would be the right one for say a 1000cc bike. The battery I remember using was the Yuasa (YuMicron) Y60-N24AL-B which has been replaced by model 53030. They list a model 51814 for a /5. You can find out more on the Yuasa website...

[phil]

My 1974 R90/6 had the same issues. It was a weak battery. I put it on the charger for the night.