Headlights draining Battery

[Kwaka59]

Hi i am new member to the ZXR Owners Club, having recently bought a 1991 ZXR400L. I am a 46 year old biker and should have bought one years ago!! Not stopped grinning since. However i have an annoying electrical problem, well i think it is anyway, the bike sometimes has difficulty in starting especially after a short run. I have had a multi meter on it and the charging syatem seems to be working ok, rise in voltage when revved @ 4000 rpm, but when i swith on the lights the voltage drops quite consdirably, side beam ok, main beam starts dropping. Is this normal or have i got a fault somewhere? assistance greatly received cheers.

[RedexRobB]

Hello and welcome to the forum.

What voltage are u seeing at 4k rpm? Iirc should be 14.5v. Could be that ur charging circuit is fine but the battery has had it.

[Kwaka59]

Hi Cheers for your reply, I am getting a reading of 14.5v + @ 4000 rpm, it drops below 13v- when the main beam is kicked in . The guy i bought it from informed me he had put a new battery on the bike just before i had it. Not sure what to check now. I did try doing a resistance check on the reg/rec but not sure what i was looking at really, got some readings across some connections and nothing on others. Dont know what to try next!!

[RedexRobB]

The manual is on the main site should you need it

http://www.zxrworld.co.uk/zxr400/manual.html

that will have the electrical tests for different bits and what results you should expect.

Ive just re-read your post and actually it sounds ok to me. When you say main beam drops, do you mean drops in brightness with engine speed? If so then yes thats absolutely normal.

[Kwaka59]

no when i mean it drops, i am referring to the voltage. It drops off from 14.5-15v down to just over 12v!! The lights dont really dim at all.

[RedexRobB]

Oh I see, it sounds ok to me. The fact your drawing additional current for the head lights will cause the voltage to drop.

[Kwaka59]

Cheers for that, but i still cant understand why sometimes i go for a ride, 10-15 miles or so and when i come to start the bike to return its like the battery has been drained!! This has happened several times, last was a 10 mile trip to drop my lad at his mates, turned the bike off for about 30 secs went to start again and nothing, had to bump start it!! Confused!!

[RedexRobB]

sounds like the classic hot starting problem to me:

viewtopic.php?f=166&t=3391

[Kwaka59]

Whats that???

[RedexRobB]

Some people, not all, have trouble starting thier bike from hot. For example they fill up at the petrol station go to start it and it turns over slowly and doesnt start. Leave it 15 mins to cool and it tarts first time.

Yet to find what the cause is unfortunately.

[Kwaka59]

Sounds like i'll have to do some further investigating or live with it, Thanks alot for your help much appreciated.
Hopefully one day i will get to the bottom of it!! until they i will try and keep grinning!! Thanks again.
Will keep enjoying the site.