Tacho 'bouncing' when starting - ZXR250

[SuperDave]

Went to take my full license test today on the trusty ZXR250 and as luck would have it, I ran into some starting trouble.

As I pushed the starter I noticed that the tacho needle shot up and then fell down. I think it did this a couple or so times as I held the starter in. Starter also sounded weak - result of low battery charge I assume.

I managed to crash start the bike and it ran fine from then on except one time during the test when I was slowing down to stop and the bike just cut out - Quickly dumped the clutch in 2nd and it started again. No other trouble for the rest of the ride from then on.

Any body have any idea what would cause the tacho needle to move like that when trying to start the bike?

[kickingzebra]

Tachos in cars are often electrical impulse driven off the alternator I guess... If it doesn't noramlly do it, then the battery going flat by itself may have something to do with it, or check voltage rectifier and charging circuit.
At least you got the full?
Can move on up to a bigger bike, without worrying too much...
(if only it was always that simple...)

[.produKt]

Yea your're right thats just the result of a low battery.

But how far does it jump? when i killed the battery trying to start my mbike after it arrived off the truck it jumps about 3 k, then the starter motor just styarted clicking.

Just charge ya battery overnight once charged grab a voltmeter to ensure the alternator is charging the battery @ 14 ~ 15 Volts @ 4000 rpm, and the alternator output voltage is 25v or more @ 4000 rpm :)

That should sort out if you have any charging troubles.

[Big Chim]

man what a way to make an impression on the instructor for your test, crash starting the bike.

Congrats on getting it

[.produKt]

Hehe Roadrash.

Ahh well SuperDave... At least ya have a decent bike..

Got any pics?

[SuperDave]

Hell yeah! Everything bad happened during my test, bike problems, pissing down with rain and to top it all off some bitch goes and cuts me off real hard without any warning - even had my rear fishtailing!

But yeah I passed which is great, looking for a 600 now. The reason I want to know whats wrong with the bike is that I'm just about to list it on TM and would like to give a rough idea of what may be causing these recent problems.

The problem must be something electrical, voltage rectifier, charging circuit, alternator or something along these lines. Someone mentioned something about it could be trouble with the coils or maybe the condenser? Could this be?

I think it the needle jumped to about 8k or so.

[kickingzebra]

Unlikely to be coils... you would notice the bike running on 3 or loosing power etc first

[SuperDave]

Oh sweet, powerwise the bike is fine - still pulls hard. Must be something electrical from the the looks of it. It's quite intermittent too.

Thanks everyone for the help.

[imdying]

Don't sweat it, just charge it and flog it on tardme. Problem with ZXR250s is they're all heaps that are getting old. Damn shame you can't buy a 2006 model instead of all these high k crappy imports that get dumped here :(

[WINJA]

re the tacho bouncing , it happened on my zx9 and it ended up being a dry joint on a battery terminal

[John]

also just check the right hand side loom going through the frame that 10point (??) connector is suseptable to rust so CRC it all and check the wires for visible damage or possible rust.

[SuperDave]

Thanks for advice so far - I've just taken some reading with the voltmeter. Found some interesting things, I'm not sure on the exact figures but this is the rough idea, hopefully from these one of you fellas will be able to give me further advice.


Battery Voltage before starting up the bike, it was ridden yesterday and has been sitting since yesterday morning = 11.7V

Battery Voltage after letting bike warm up and whilst holding the revs at approximately 4500rpm = 13.5V (note this is without the lights on and without the radiator fan running)

Battery Voltage holding at 4500rpm with lights on and radiator fan running = 11.9V

Now .produKt mentioned that the battery should be at 14 - 15 Volts whilst holding the revs at 4000rpm. My bike is quite a bit off that without the drain of lights and fan but with these on it falls very short.

Is this an indication of a fucked battery? This battery is only about 9 months old but if we ignore this, would you reckon it all points to the battery?

[John]

I still stand by it being a wire, lift the tank and check all those cables - check your earth - those voltages arent to bad and seem perfectly fine as to not be an excuse to run correctly.

[.produKt]

Hey superdave.

What i mentioned was from the electrical Chapter of the Kawasaki ZXR250 Workshop manual.

I got it from a link posted on this forum site but i cant find it again. So i've ftp'd the electrical chapter for you
http://www.phattpad.orcon.net.nz/15-electrical-system.pdf.

I think it was saying that the voltage of the battery with the voltmeter held on the terminals while running is meant to be 14v.
Without the engine running its meant to be about 12v. and with the voltmeter directly on the alternator terminals should be 25v or more..

Its in the pdf file :)

[imdying]

Yeah, sounds like a bad earth in the charging circuit.

[zeRax]

sounds like what i had, i checked all wires too etc and it wasnt them.
after allsorts of testing found it to be rectifier and got a new one and that fixed it