My guess is you got 20 to 40 watts to spare.  But I wouldn't use it.  It's not good to run these things at full capacity.

Stock lighting is 55/60.  Lightbar will add 70, that's 130 watts.  This is a known configuration and no one's come on here and said don't do it.

You could change all your bulbs out for LED's, then you'd need to change your flasher too.  And you could put in a HID light that's super bright and only draws 35 watts.

Here is a rule of thumb that I have used successfully in the past.

with bike ticking over slow in low light conditions like pointing at a wall in garage or something, switch everything on one at a time lights on main beam 1st, then indicators and apply brake. If light beam isn't so bright then rev the engine you should see your light beam get brighter when engine revs if genny can hack it.

And don't exceed the watts for your fuse rating.

My savage, (so I guess yours as well), has 2 20 amp fuses.

watts used = amps X volts

savage fuse is 20 amps X 12 volts (savage has 12 volt battery)

20 X 12 = 240

so you can have 240 watts running without blowing the 20 amp fuse.

Assuming one fuse is for light curcuit then.

2 indicators at 25 = 50
brake tail bulb, both lit = 50 ?
theres a few little 5 w bulbs about the speedo.
so you got approx 120 watts in reserve.

you should be ok with a 100w headlight as long as you aren't powering a lot of other stuff, the main thing is don't blow your fuse!

I think you have read my post asking about charging voltage? My electrics copes fine but I get a bit under 14 volts across battery and I am not sure why, seems like a tired out battery is favourite, when I have new battery I will post what voltage I get then!

Rustbucket, were the 2 driving lights in addition to the headlight already fitted?
In my calculation you have 120 watts spare to run your headlamp, so a 100w headlight should be Ok.

If you have 2 55 watt driving lamps plus your headlamp that is 60 + 55 + 55 = 170 watts. so you are running at 50 watts over max design for the fuse rating.

If you just fit a 100w bulb in place of the standard headlamp bulb you will be 20 watts below max capacity when you hit brakes with indicator going, so it should cope with charging battery and not blow any fuses!

According to the book, the XM draws 2 amps, maximum.  I'm going to try it.  Worst case scenario:  I get to listen to the radio while I wait for someone to give me a jump.  In the rain.  When I'm late to work.  And I have chest pains and can't drive to the E.R.  Holy smokes!  Maybe I better not do this thing?

I have one of those sitting on my desk collecting dust.  When the battery quit taking a charge, it was way to expensive to get a new one.  The thing never worked as a walkman anyway.  It got terrible reception.  Battery life was only about three hours when it was brand new.

The only reason I still have  it is that I'm a packrat.  You never know when I'll need a spare ribbensnort demodulizer.  I'd hate to throw this thing away and then learn it was equipped with two of them.

Well, I got it hooked up.  The XM unit requires that you use the included 5 volt adapter.  It's for a cigarette lighter.  I took it apart to see what was inside, and it was a bunch of solid state stuff that was too complex for me to understand.  So I kept it as-is.  I mounted a new fuse holder connected directly to the battery and installed a 20 amp fuse.  Then I mounted a power outlet where the old reflector used to hang (right above the header pipe, which will probably be my undoing).  I plugged the XM in and rode away into the sunset laughing my head off to Brian Regan.

5 volts X 2 amps=10 watts, if I've got that figured out right.  I figure the thing ought to handle 10 more measly little watts.