Voltage Checks

There will be a volt drop due to the ignition starting various cycles in readiness to start the bike, i.e dash lighting and the engine management etc. As long as the bike starts without issue with that voltage it shoudn't be a concern and once started the alternator kicks in and the volts should go upto 13ish.

 

Not sure where you are measuring the voltage, but 9 v sounds really low. If the bike is fuel injected, when you turn the ignition on the fuel pumps will reduce the voltage, but not that much.

Can I suggest you get hold of a known to be good battery, and link it to the bike battery. Then check again the voltage drop.

This will help to diagnose the state of the existing battery.

 

Sorry mate your post only said when you turn the ignition on the volts drop and nothing about the bike turning over and not starting. How old is battery? Does the bike turn over at it usual rate or is it slow? Would be worth drop/load testing it, your local bike shop will prob do foc. If its a gel or glass mat battery they don't generally last more than 12-18 months. In the mean time as a test for piece of mind grab some jump leads and hook it up to your car, if the problem goes away its kinda proved the fault lies with the battery

 

If youre measuring to chassis from each side of the fuse and you have a volt drop of 3 volts you have a problem with the fuse or fuse holder.

If youre measuring from the chassis -ve to the negative connection at the ECU then you have either a broken wire or bad connection there should be next to no reading at the -ve connection point of the ECU from the chassis earth

 

May help to know what bike you have - for example a Rocket 3 that has not been modded will have a significant drop due to the lighting.