Tunnie. 

Without knowing your exact situation...  year, model, lights or no lights, etc. I am very hesitant to give any advice.  Best is to keep battery in most situations.  You can end up with expensive issues if you don't. 

The questions you are asking sound pretty basic and the answers are most likely "no", but again, would need to know your situation.

Hello, what it is is a dt100, I’ve been messing about putting leds in the tail and indicators, this gave a great tail light, okish indicators on the left and not very good on the right. They also had a slightly unclean flash. Last night I had the idea of trying with the battery disconnected and this gave brighter lights and a great flash. I had been prior to this running two 6 volt batteries wired up and pre charging them to keep the lights ( esp indicators on better) this was when it had normal bulbs. )

It’s a 1983 model by the way

What I ve tried now is battery in, filament headlight bulb out. Indicators seem better, or might just be my imagination 

This might help with your indicators.
I would think that the draw from the LED bulbs isn't enough to enable your existing flasher relay to operate correctly.
www.yamaha-enduros.com/index.php/forums/...14993-led-indicators.
Good luck.

Thanks Pete for that info, all the best