How bad is the pulling? Is it only a slight drift or hard enough to yank the wheel from your hand?
Is it a hard pull, and the only time it pulls under braking? If so, I would look at the calipers, particularly the one on the RIGHT, as it pulls to the left. The right one may be laying down on the job. I have also heard of the soft lines to the caliper becoming internally clogged, and this may cause one caliper to get less fluid than the other. Maybe? That is a rare one for me.
The slight pull is different. Could be one set of pads seated differently, one one caliper is a little more worn that the other? Also may want to consider rotating the tires, to see if it goes away. Could be a tire problem too.
Good luck. Let us know the results of your efforts.
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)