I asked a similar question myself not too long ago:
http://forums.sohc4.net/index.php/topic,146822.msg1671093.htmlI ended up sorting it out, but I guess I never posted a follow up
will do that next..
To answer your question, although you could, no you should not combine the four wires: Brown, Brown, Brown/White, and Black together right off the ignition switch.
I know you have two key positions: ON/OFF, but how many terminals on your aftermarket switch? Just two? Or three? Some, like mine, have a third "accessory" terminal. I'm gonna assume two on yours...
So your one brown/white wire and two browns (and make note: the browns are effectively the same wire—they jump together right after the switch) are there partly to arrange the "parking mode" of the bike. i.e. when the the stock ignition switch is turned to that third position that I've never had any use for anyway. Parking mode bypasses the taillight fuse circuit to give power to the taillight directly from the main fuse via the ign switch. So just throw away the concept of parking mode with your new ign switch.
As calj said, retaining functionality of the fuses is good, and really easy to do in this case. I think the main thing to understand here is how current flows as he began to explain. It comes from the battery through the red wire, to the main 15A fuse, then through the main harness to your ignition switch, where the wire then is switched to black. At this point, current is only flowing from red to black and then through black into several connections in the headlight bucket. The ign switch does NOT supply current to brown and brown/white from red at the ign switch. It actually connects brown with brown/white, which is getting its current from black, but from a connection in the headlight bucket. So let's trace brown/white back to where it jumps off black...
If you look in the headlight bucket, there's a brown/blue wire with a little black tube and male bullet connector end. It's plugged into a female connector that is jumped right off the black wire. Then that brown/blue takes current through the main harness to your fuse panel, through the taillight 7A fuse, and then becomes brown/white. The brown/white wire then runs back through the main harness and lights up your gauge backlights, AKA tach/speedo illuminating lights, and also runs to the ignition switch. At the stock ignition switch, in the ON position, brown/white is joined with brown—brown then runs to the taillight to illuminate it.
The reason head/tail lights have their own fuses is they have a higher risk of shorting out because they are constant/running lights. So by design, if your tail/head lights cause a short while you're out on the road, they'll blow their respective fuses and stop illuminating, instead of blowing the main fuse, rendering the entire bike dead at 60mph on the freeway. So think of your head/tail light fuses as being "nested" within the main fuse circuit. They can't blow the main 15A fuse because their own 7A fuses will trip first.
So again, no you should not combine the four wires: Brown, Brown, Brown/White, and Black together right off the ignition switch. Doing so will render your taillight fuse useless. So your best bet is to hardwire (twist/solder/shrink tube) your brown to your brown/white, completely independent from the ign switch. Problem solved. Fuse functionality remains intact.
You can probably get the job done quicker than it took me to write this response. I've spent what seems like lifetimes sorting through my electrics through the years. I enjoy sharing anything I've learned along the way. I could have just left the short answer, but teach a man to fish or something?
