should i skip the testing altogether and just get a new RR? since i could risk blowing out the new bulbs (is this a possibility?) and mess up the cdi (as petrolhead19 suggests) by firing up the possible failed RR on a new battery (and maybe even ruin another battery?). or am i overreacting?

what do you guys think

Well the reason for a battery expanding and deforming is due to over charge, which will be a diode or 2 which hbad in the reg/rec and sending all the volts from the genny to the battery charging it at high volts.
And yeah it can also pop your bulbs, if you put a new battery on without changing reg/rec it will most definately kill the new battery aswell bud, and possibilty of doing the cdi damage.

Adam

The liklihood is that it IS the reg/rec that's caused the issue, and if it hasn't died, it probably at will at some point between now and forever so having a spare isn't exactly a disaster. I doubt that putting a new battery on and running the bike for just enough time to measure the output would kill a new battery, however it is entirely your choice and if a new battery and a new reg/rec sorts it, then that's good enough. Personally, I'd want to test the old one to see if it was definitely overcharging the battery rather than the battery being crap, although if your headlamps were blown a bit before the battery went it's pretty damning evidence against the charging circuit.

Dont't rev it high just connct the multimeter and start it.

If its putting out more than 13-14 volts at idle kill it straight away.

Ive often used a big bulky car battery for this test as they have thicker plates so for a few seconds the over-charge is much less likely to hurt them.

will the multimeter test be reliable if i do it without any light bulbs in?

Yes - forget about the light bulbs, they are a distraction.

The reading will be higher without lights on, but only by about half to 3/4 of a volt at idle. I'm pretty sure that in theory, the reg/rec shouldn't pass out more than the absolute safe limit of 15.5V regardless of lights or not as it's supposed to compensate for load - hence being a regulator! The reason people usually test at 5k with lights on is because this represents the highest load the system will be under and is a way of telling if it's weak, rather than overcharging.

make sure your positive wire didnt touch the sub-frame . itl short and heat and deform.

okay guys. I got a new battery now and I borrowed the reg/rec from my CBR250RR (never had any electrical problems). At idle (without light bulbs plugged in) it gives 14.8-14.9V and at 5K rpm 14.4-14.5V. It see the same values when the reg/rec is hooked up to the CBR250RR.

What do you guys think? Isn't it odd that the voltage is lower at 5K RPM then at idle? also, the numbers look a little high but that might due to the fact that the light bulbs aren't plugged. will set them up tomorrow. I also got a fresh reg/rec coming in next week but I thought that I could use the reg/rec from the CBR as a temporary solution until I get the new one

You'll probably be down to about mid 14s all over with the lights plugged in. That's very healthy, but not excessive.