Morning all, the coil on my B40 gets very hot is this normal..
May get a little warm when the engine has been run for a while, but shouldn't get hot.
Is it hot with the bike not running? Is power getting to it when switched off?
Main causes of a coil getting hot are 1. Breakdown of the wiring insulation inside the coil due to old age or 2. Faulty HT lead/plug cap leading to an excessively high resistance.
Before replacing the coil and HT leads, check power no power is getting to it when the bike is switched off. I had a temperamental on off switch which cut off the engine but I was still getting some power leakage.
The bike runs for about 5 mins then stops, the coil feels very warm. I've noticed that when I switch the bike on fist time I get a negative reading on the amp meter. After the bike has stopped on me when I switch it on again I don't get a reading .
If the ammeter is working properly, there should be a slight discharge when the ignition is first switched on as the coil primary circuit will be energised. When the bike starts this should go to a positive reading as the alternator should be putting out a charge.
If your ammeter doesn't give a reading when the bike cuts out this suggests an open circuit. If you can check with a voltmeter the reading at the coil feed when the ignition is switched on when the bike cuts out and you get a battery voltage reading, then this suggests a faulty coil.
Couple of other points.... (no pun intended!)
Assuming that you have points ignition, the current drawn when you switch the ignition on will depend on whether the points are open or closed. Closed is more common just due to the effect of compression and valve spring pressure when the engine last stopped but the engine can stop with the points open too.
If the points are open there will be no current drawn when you turn the ignition on (assuming no other devices drawing power). If points closed it will be noticeable. Leaving the ignition switched on with the points closed will heat up the coil and is best avoided.
Cheers,
Bernie
Yes that all makes sense, I think the pints where closed as when I kicked it over I got a negative reading. I was also drawing 4amps when I switched the ignition on. Friend of mine is going to lend me a coil so I will try that. Thanks for advise.