As above been checking voltage on my bike started from cold on idle 12.4v at about 4k rpm 13.5
check again when bike was warm idle 12v 4k rpm only 12.4v so I'm guessing rectifier kaput when I touched it it was red hot as in burn your fingers off hot is this normal?

Yes..they get bastard hot

Yes thats how they work, turning unused electric to heat, shunt type. But my newer style mosfet type barely gets warm.

I would add that your voltages seem a tad low, check your alternater voltage, which should be about 50 volts on the yellow wires before the rectifier. Also the regulator voltage at the battery should not go over 15v at a high revs. 12.4 seems a tad low I would be aiming for at least 13.8..

Cheers mate I'll check the voltage later
I get 13v on idle when cold but voltage drops as bike gets warm

kstation wrote:Cheers mate I'll check the voltage later
I get 13v on idle when cold but voltage drops as bike gets warm

That is not very good mate.... You need 14+ to charge the battery

You can add heat sink compound ( for a PC CPU ) to the back of the regulator to aid in cooling as this aids heat transfers to the heat sink better.

I have seen other mods where there is a CPU fan attached to the front of the regulator which blows air over the regulator at all times. Though this was in the day when the tinterweb didn't exist, people could not understand why their brand new Honda reg/rectifiers kept going pop ( because they were crap it turns out ), people tried to find their own solutions.