Regulator/rectifier heatsink fitting

The regulator/rectifiers on VFR750, VTR1000, Blackbirds and CBR900 are known to have only a moderate life. One theory is that they run too hot. In Australia we have noted that in about 25% of VTRs, the reg/rec dies at about 35,000 kilometres (22,000 miles).
They can fail in two ways;
- open circuit, where they simply will not charge and the battery will die and
- closed circuit, where the fuse will go
There are a few VFR websites detailing this mod.

The VFR800 has a bigger, heavily finned reg/rec and we believe this will appear on the 2001 VTR as well.

The heatsink and fan was $10 from my local computer market (check that it is 12v), the heat transfer compound (in a small tube) was $5 from an electronics store and I already had the silicone sealer.

Remove the tailfin by unscrewing the two allen head screws at the front (don't drop the inserts), the two philips head screws above the taillight and the two plastic philips head screws underneath the rear. Remove the two taillight bulbs by turning anticlockwise. Spread the tailfin a little at the front and move it backwards, then up and forward to remove.

Front view

The reg/rec is supposed to shed heat by its metal base into the frame. This is not particuarly effective and its casing also gets very hot.

Unscrew the two mounting bolts from the reg/rec.
My heatsink was slightly longer than the reg/rec so I cut a small recess in the lower end. I then applied silicone sealer to the top of the reg/rec case to fill the hollow then placed the heatsink on top (you need to fill the air gap for good heat transfer). I made up two small 'z' brackets that go under the mounting bolts to hold it in position but this is probably unnessecary as once the silicone sets, it is doing most of the work.

I conected the black (negative) to one of the mounting bolts (earth) and extended the red to one of the taillight bulbs and inserted it into one of the brown wire sockets. I cable tied it to the wire. (Yes, I know its rough).
In Australia our head and taillights come on with the ignition so the fan spins whenever the bike is running. If this is not the case then you will have to find another source of power.

I then placed heat transfer compound on the base of the reg/rec and screwed it back onto the frame.

Some people have suggested that a fan designed for a personal computer will not last. This heatsink has been on my bike for 7 months and 13,000 km to date.

Side view

Will this give my reg/rec a longer life ?
I don't know. I do know that both the rec/reg and the adjacent frame now run noticably cooler (VFR sites claim 20-25 degrees). I figure this is a cheap mod so why not give it a go.

Rear view close

From newsgroup;

and some of the www FAQ's
(written by Andrew Sainsbury from Canberra).

I've been thru 2 reg/rec's and 2 batteries due to reg/rec issues.
If your in Sydney, call by RB Imports at Caringbah and get the
rebadged reg/rec (mines 25k km old now). Afterwards, pay a visit to
Tandy and wack a big heat sink on the sucker.


>~From the VFRList.
>~Date Tue, 31 Aug 1999 034832 -0700 (PDT)
>~From Jeff Hardy
>~Subject REPLACEMENT REGULATOR!!!! Re Bad Regulator Bulletin !!
>~but RB Imports in Sydney have regs made by the same
>~factory as Honda shit and importted under teh DAYTONA brand..
>~the regulator number is(#31600-MV4-000)~Daytona number 32828
>~oh and it was $130 NEW. compared to $224 Honda price.