Topic: Battery Dies After Riding

[boticki]

Recently bought a 77' 750f. Finally got it running well enough to take it out for a decent ride. Went to start the bike up about five minutes after shutting it off and the battery was died. Bike ran well the whole time I was out.

What could be wrong? I remember reading a thread recently an the issue ended up being the rectifier. Can't find the thread now, of course. What all can I check?

[Randy]

sounds like the rectifier.. i would charge the battery, start the bike and throw a meter on the battery to see what the voltage is.. also there could be a short.. so check the bikes wiring... see if there is bare wire, burnt or discolored wires..

[Stev-o]

Sounds like a bad battery, may not be holding a charge. Any idea how old the battery is?

[flybox1]

your charged battery should show 12.4v.

read this..

http://forums.sohc4.net/index.php?topic=93865.msg1048441#msg1048441

[Rigid]

Plug that the 3 yellow wires go into behind the engine is a weak point.  Told a guy from church that was probably his problem without even looking at the bike.  That was it, now he thinks I am some sort of Honda god.  Nope, just seen a bunch of them fail.

[Spanner 1]

How long is a 'decent ride ?........... if 50 or more miles then looks like your charging system is operational but feeding a battery that is not holding the charge . Are the battery levels above the min. electrolyte mark ?

[72500john]

as spanner1 said make sure your battery is up to snuff. a good working charging system will not charge an old tired battery. from there check your rectifier. simple doide check..diodes are either good or bad..not much in between. from there make sure you regulator is adjusted properly.pointgap,air gap and voltage adjustment. i beleive you can find all the manuals for your machine at this web page.
one other thing to check which i ran into and found info on this forum is the case of having high resistance connection to your regulator battery voltage monitoring wire..aka if this wire has high resistance which equals a voltage drop. meaning the voltage regulator will see a low voltage and pour the charging current/voltage on and in essence cook your battery. mine was a simple fix by cleaning the connectors for the ignition switch plug and at the bracket under the side cover.
hope this helps.

[Duanob]

I notice when there is a charging problem everyone takes the shotgun approach at diagnosing it. It doesn't really work.

here is a systematic approach at diagnosis and it worked for me.

http://www.oregonmotorcycleparts.com/FAQ.html

[TwoTired]

Resist any urge to adjust the regulator.  It is the last thing the touch AFTER verifying all the rest of the components are working a designed.
The components are:
Battery
Rectifier
Stator windings
Field coil windings
Interconnect wiring
Voltage regulator

I will say that even with a fully functional charging system and battery, if the bike uses more power than the alternator can supply, the battery will deplete to exhaustion.  The 750 has 210 watt alternator and a stock bike uses about 120-130 watts.  If the bike is modified to use 220 watts (for example), then the battery can't be charged up by the bike.  Finally, the alternator makes 210 Watts at 5000 RPM.  At idle, it only produces 50-60 watts, while the bike is still using 120-130.  So, even the stock bike will drain the battery during prolonged idle.

Cheers,

[curemode2002]

+1 Duanob and TT
These guys are both right and TT did an awesome job helping me suss out my chargeing issues on my CB650.

[Duke McDukiedook]

Look at the things TT says to look at and you need to look at how old that battery is probably first- if it is older than 3 years or you just bought it that would be the first thing I would suspect. Most people throw a crap or dying battery in before selling it and then shove that cost on to you to replace.

Making sure it is fully charged before checking it is one thing you want to do first.

[HonderCB]

Cleaning all terminals that connect to anything in TT's post is a good start.  Use a spray can of electric contact cleaner and spray them out, let them try, then put them back together... may just be simple corrosion.  That solved my problem, charging system works great now and i didnt spend a bunch of time troubleshooting complicated electrical components when i didnt have to.

[fmctm1sw]

Just my 2 cents.  I worked on a '95 rebel a few weeks ago that ended up having a bad stator.  I found that by looking at the AC voltage out of it.  I also worked on esquire's 350F and found the red (and white?) lead from the rectifier to the battery was corroded.  Luckily it fell apart when I separated the connector, made it real easy.  I used this:  http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf when I was working on that Rebel...

[fmctm1sw]

I notice when there is a charging problem everyone takes the shotgun approach at diagnosing it. It doesn't really work.

here is a systematic approach at diagnosis and it worked for me.

http://www.oregonmotorcycleparts.com/FAQ.html

Hey..  That's a pretty good read...

[Duanob]

I notice when there is a charging problem everyone takes the shotgun approach at diagnosing it. It doesn't really work.

here is a systematic approach at diagnosis and it worked for me.

http://www.oregonmotorcycleparts.com/FAQ.html

Hey..  That's a pretty good read...

It's an awesome read. I was all set to buy a new alt and rectifier and everything else. I followed the OMP FAQ diagnosis and found three main wires were bad. I replaced them and still had problems. Did the diagnosis again that pointed to bad wires. Dug further into the harness and found more bad/burnt wiring. Replaced it and now the charging system works perfect. Even replacing all the components in the charging system would not have fixed the problem, just a few bucks in replacing wires. I love that site.

I also bought some new wire blocks and I will buy a new fuse block from OMP this winter.