lights dimming

Can anyone please help with my problem?
I have a six volt system on my dax and i have fitted 6volt/21watt bulbs into the indicators.
Everything is working but when the headlight or just the sidelight is on they dim in time with the indicators. I have a honda flasher unit rated at 18/23 watt and good earths to all lights.
When i rev the bike with everything switched on, she starts to splutter as though its running out of fuel but as soon as i back off the throttle a tad, she purrs away.
I suppose my question is ....is this a normal occurance on a 6 volt system and if not....what can i try to eliminate the trouble? The battery is in good condition

I'm afraid that's pretty normal...apart from the spluttering.

As already said,its pretty normal,the electrical system is fairly basic and primitive.
Reducing the wattage of lamps to say 8 watt with corresponding flasher unit helps.
One member has I believe fitted a LED kit succesfully,
Personally I now use hand signals if need be !

Thanks for the replies folks. I had thought it may be the case but its always nice to be informed.
As for hand signals........thats what i have been using but it really is amazing just how many people on the road have no idea whats in the highway code! Stay safe and have a great summer chums.

I suppose it could possibly be the coil breaking down that may be causing the spluttering. As this only happens at full revs with everything switched on. I have read somewhere that you can use a 12volt coil on a 6volt engine but not the other way around. Can anyone confirm this please?

Not confirmed.
It's the other way round.
12v engine 6v coil = OK

Take a good look at the earthing of the coil (paint, rust, dirt...)

As Waynus said, Do the simple stuff first, ie check that you have a good earth. Spark plug is it new? Suppressor cap/HT lead may be breaking down under load. Oh and the really daft one but happens to a lot of people including me - make sure there is petrol in the tank .