Topic: Electrical problems CB750f

[Reverend66]

I just purchased a 1976 CB750f and have been in the process of tuning/cleaning carbs etc. The other night I  put the battery on a trickle charger because I had drained it starting the bike over & over. I installed the battery (now fully charged) turned on the ignition everything lit up fine, once I pushed the starter button *click* and now no electrics. I took off the side cover & cleaned all of the connections well and it lit up again. Once again puched the starter button with the same result. Did the same thing got the electrics back & kick started it & it ran fine. Has anyone else ever had this problem? I didn't mess with any electrics other than charging the battery untill this happened. Any suggestions would be greatly appreciated.

thanks,
Darren

[OldSchool_IsCool]

What is the history of the battery?  Does it trickle charge "quickly"?  an old, weak batter will charge quick and can sustain a running engine but will lack the balls to pump out the 100+ amps the starter demands.

[Reverend66]

Before I charged it the starter worked fine, I just ran it down while I was tuning the bike. It's not blowing fuses and once I clean/fiddle around with the electrics it will light back up again. I figure it's a loose connection/corrosion, just wondering if there is a common culprit.

[NitroHunter]

I've had that same thing happen.
It could just be the battery has reached the end of it's life. Is there white stuff where the battery water level should be? Sulphated cells? You won't necessarily see any of that though, these batteries are only good for a few years. Load test it to be sure.

FYI - When you do replace it, most times a new battery comes 'dry charged' and the purchaser must fill it with the supplied electrolite. After filling to the proper level, MAKE SURE you allow it to stand several hours - overnight is better - BEFORE you trickle charge or use it. This process makes a noticable life difference. After multiple battery warrenty claims, a bike shop I worked at ended up with a factory rep on our door step to tell us this... surprise, it worked.
Keeping a floating trickle charger on it when not used for extended periods is a great plan. The batteries I've actually done this to have lasted years longer than when I haven't done it.

[Reverend66]

I was afraid it might be the battery, I'm just confused as to why the lights will quit working only to work again after a bit of messing about with the wires.

[Steve F]

The situation that you explained sounds exactly what happens when the battery terminals are not tight enough.  You get just enough current initially to allow things to "light up", but as soon as you put a heavy load (starter), the terminals cannot carry the current, and "click", everything goes dead.  Make sure that the bolts that you're using on the battery terminals aren't too long where the screws bottom out before getting tight. 
Another cause is the connections inside the battery that go from one cell to another are cracked and seperated.  The same thing happens here too.

[my78k]

This may seem ridiculous but it just happened to me the other day on my CBR. Exactly the same issue you describe. I turn it on and everything lights up etc just like normal. Hit the satrter and nothing! Everything goes out!! I dig out the main fuse and it is fine. I do a bunch more digging and still nothing.  Pull the seat off to get to the battery to do a reading and...

Turns out that one of the battery leads had somehow come loose. Not sure why it would act as described but as soon as I tightened it up everything was just fine!!

Again, I know this seems dumb but you may just want to double check it.

Dennis

Edit - darn steve you beat me to it!

[Steve F]

Edit - darn steve you beat me to it!

 
Good call, though!

[HondaMan]

Also: try changing the fuse, or jumper across it temporarily to see if this fixes it up. Steve's tip is most likely, but the fuse/fuseholder can do this, too.

[BeSeeingYou]

+1 on the loose battery connection.  Check to see that they are clean also and hit them with a file or sandpaper if not.

I posted this earlier in another thread but it seems appropriate here.  I was out riding one day and the negative wire came loose and the nut that sits inside the battery post disappeared.  I used a stick to wedge the wire onto the post and though it would not make a good enough connection to use the electric start I was able to kick start it.