Battery problems?

Hi folks,
I have a problem on my 2003 FE 400 and was hoping for some advice.
With the ignition switch turned ON I have no lights, horn, starter….nothing. But starts first time on the kicker. Ticks over, runs great. With the engine running the lights work; well sort of. At tickover the side and headlights are quite bright, but if I rev the engine the main beam goes out and the side goes very dim. Surely this is the opposite to what should happen.
Bike has 8000km/200hours on original battery so have ordered a new Yuasa YTZ7s.
Advice I have, so far, is that my Rectifier is shot and this is why my battery is flat and explains the lights also.
Can anyone confirm this or come up with any other comments, thanks in advance.
Paul in Driffield, Yorkshire.

That almost sounds like a short circuit, or a bad ground. Try the rectifier and battery first though.

Thanks Bendberg,
have ordered a new battery and rectifier from DCR here in UK.
Have been trawling UHE and recon a Digital Multimeter might be usefull for me.
But there are so many available!
Any reccomendations?
PS: had the berg out round town today. Starts first kick and runs really well. So not my stator, or is that wishful thinking?

Paul..........

FWIW SM610's 04 FS450E YTZ7S battery also gave up the ghost recently.

Maybe 4 years is the normal lifespan of these compact batteries.

As long as your charging system is reading 14v-14.4v when the bike is running the battery should recharge.

The multimeter needs to do OHM's, DC voltage minimum. You will find most meters will do the above and AC volts, AC/DC amps, continuity of circuitry. If you are only using the meter to troubleshoot your current situation, I would say to price shop the meter.

Paul - Is your bike one that has the regulator and rectifier in a single unit or are they seperate?

Have you tried connecting jumper leads to another battery & measuring the running voltage? Confirm your battery os OK before opening the packaging of the new regulator/rectifier unit as you may be able to return it if not needed.

What you are describing sounds like the battery is probably the only thing that has failed by going open-circuit. It would appear flat because it is stuffed, not because the charging system is not funtioning. Jumping another battery across it would temporarily fix the problem if that is the case. If the battery has failed it should not take out any other components with it.

When you rev the bike without a functioning battery and not much electrical load the regulator effectively shorts most of the stator output out, dropping the average system voltage to the point where it is probably too low to light up the main beam but enough to tickle the side lights.

Since the bike starts & runs well you must have good spark, so the magneto part of the stator must be OK. The 12V charging coils rarely fail so it is unlikely your stator is faulty.

With digital multimeters, often ones aimed at automotive applications have an inductive pickup tachometer. It uses a clip that goes around the spark plug lead to sense when the plug fires and uses this to measure engine RPM. This is handy on a bike without a tacho for confirming gearing etc. They also usually have a 10 amps or better current range which is handy fixing charging system problems. They tend to be a tad more expensive than run-of-the-mill meters but are probably worth it. The one I have is a Fluke 178 (I think). Fluke make excellent meters but there are cheaper ones around that work just as well.

Thanks for all the help chaps.
Rectifier is located on the plastic rear mudguard under the seat.
Will get a meter today and perform the tests you suggest and report back.
The way DCR explained it my rectifier has gone and the battery has drained. Since it's the original battery I think I'll replace that. Have sent off for a Optimate 3 charger also.
So I'm off to York for a Multimeter.
Paul.........

kipperthedogs said:

Thanks for all the help chaps.
Rectifier is located on the plastic rear mudguard under the seat.
Will get a meter today and perform the tests you suggest and report back.
The way DCR explained it my rectifier has gone and the battery has drained. Since it's the original battery I think I'll replace that. Have sent off for a Optimate 3 charger also.
So I'm off to York for a Multimeter.
Paul.........

Click to expand...

I got exactly this behaviour on my bike when after the main fuze was broken. I just simply replaced the fuze and then everything worked fine. The cause of the broken fuze was myself (or the tree!).
/Christer FE501-02 with -03 electric system

Funny you should say that husa...just got back in from garage.
Borrowed a multimeter and got 12.37v through the battery.
So had a close look at the fuse area.
BINGO! Little clip between one side of fuse and right terminal on relay(?) was broken.
So it looks like I'm sorted for now.
I'd just like to thank all those who contributed on this, thanks folks.
Paul............

Another simple battery symptom/fix to watch out for.

The battery terminal bolts may sometimes vibrate loose causing weak starting symptoms. If you experience weaking e-starting check the battery terminal bolts.