..... When I revved it dropped to 12.9v is that normal
Yes. 12.9 is getting a little on the low side tho'.
The unit snowy is referring to does not "fit" directly. It is however a huge upgrade. Look up the "charge mod". Ask any questions you may have...Ok thanks mate. Does the r/r from a zzr1400 fit? I think I read somewhere it does?
Next test is to measure the voltage at the brake light connector. Need to see why the lamps are blowing.
Just checked there now the brake light reads 12.6 and then 10.6 when the brakes are pressed?
The tail lights are still working but seem very bright. They are reading 12.8v
Snowblind, what is leading you to this suspicion? Even if such a short existed, the bulbs should be able to handle the 15 volts coming out of the R/R. Help me Obiwan....That's an excessive drop for a couple of brake lamps. I suspect you have a short from the R/R output into the brake light rails.
Your charging current is being diverted into the brake lights.