
Originally Posted by
neels
Could be faulty connection between the battery and the starter motor.
Neels and Motu are on to it.
Your battery must be in good condition, and fully charged before you start. A new battery, is no guarantee that the battery is fully charged - frequently it will be filled with acid, then you are on your way.
Your auto electrician would do a couple of things here that you can't do. He would test your battery by putting a big load on it. He would measure charge current at several rpms, and measure the current going into the starter motor, to ensure it is not drawing too much (shorted winding ?) or too little (brushes - connections / solenoid faulty?)
But you can do some tests with a basic $10 DC voltmeter...
So..
(1) Check your battery is charging. With headlight on, engine running at about 3-4000 rpm, the battery should have about 14 ish volts on it. No need to panic +/- 0.3 volts on your $10 meter.
(2) Turn bike off, remove key, Have a beer. Check battery. 12.6 volts is about right.
If you pass 1 and 2.. seems likely you have a good charging system, at least as good as you can check with your $10 meter.
(3) Now it gets tricky.
Crank bike measuring battery voltage.
Depending on the draw of the starter motor, the charge on the battery, and the battery condition, it may drop as low as 10 volts. Paradoxically, a lower drop may not mean all is well - it may indicate poor earths, high resistance cables, a faulty starter solenoid or other poor connections.
Note the result.
(4) Repeat test, measuring voltage drop across starter motor itself. The difference from battery voltage is the voltage drop across all your leads and the starter solenoid. Less is good !
IF cranking
- Drops battery voltage massively we know we have a starter motor drawing a lot of current (shorted windings, siezed motor, excessivly thick oil) OR a bad battery
- There is little voltage change at the battery but lots at the starter we have poor connections, or dodgy solenoid
- There is little voltage change anywhere we have poor connections, or faulty brushes
Good luck !
David must play fair with the other kids, even the idiots.
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