electrical gremlins.....

i have just fitted a new reg/rec to my c90 powered st and now when i rev it, if i turn the lights on the engine dies.
the reg/rec is a genuine honda c90 4 wire unit and the colours all match up (pink-pink, yellow-yellow,green-green and red/white-red/white)so i am a tad confused. another thing is that when revved she is now backfiring occaisionally which she didn't do before the change. am i right in thinking that the genny should be running the lights when the motor is running and not the battery?
i am getting between 7 and 8.5 volts across the battery when running so i am sure the thing is charging. is there any way of reducing the output so i dont boil the battery again!how can i check the reg/rec is working correctly?
please help all you electrical wizzards

Probably a bad earthing or a short circuit anywhere between the frame and the indicators.
Yes, the lights run on the engine stator, not on the battery.
But the indicators are powered by the battery.

You can check the resistance (Ohm) of the rectifier, but I don't remember the correctt value.
The orange plate doesn't work that good, it might be worth to replace it with a newer Honda silicon version.

The bike doesnt have indicators. I am going to try another reg/rec first as everything was fine before. I am a bit concerned about the voltage going into the battery as i dont want to cook another one! I suppose i will have to go through the loom but as i said, before the old reg failed,she ran perfectly. This bike does not have an orange rectifier just the four wire unit. The joys of non standard motors i guess. Thanks for your help.

Probably a stupid question but... you didn't fit a 12v C90 engine?

The points are in the head on the left side. I have been told if it has points then its a six volter. Lamps are all six volt and its a 1970 motor so it should be a six volt model. I was talking to an old biker about my electrical probs when on fullbeam and he said the six volt early honda 125s had exactly the same trouble. Ap!parently it was always a duff reg/rec. I have a honda item on its way so we will see if it helps. Getting 7.0-7.9 on tickover going up to 9.3volts when full throttle. This is way too low for a 12volt engine and way too high for 6volt i would have thought.. Come on postie

The points aren't nowhere near the head, but it is indeed a 6 volter if it's that old.
6v regulators are known to be unreliable.
So replace it with a new one and make sure evertything is connected correctly.
Battery, fuse,...
7,9v load currencies are normal for a 6 volter with a low battery.
But too high for being a constant voltage...