There are a few things not already mentioned that may cause this. Please excuse if the suggestions are ridiculously obvious, but we all miss the obvious at some point !
You have new pads ?
Have you fitted heat pads like on the back brake ? They shouldn't have heat pads on the front.
Is the rectangular tab end of the pad seated properly in the clip in the calipers
The pad spring in the roof of the calliper is incorrectly seated
Pre 2008(ish) it is possible to put the pad spring in the wrong way round.
Post 2008(ish) it is possible to get a piston interfering with the pad spring. This happens if the pad spring is not firmly held in place, and each leg of the spring is pressed at different times. The spring rocks and dislodges at one end, putting it below one of the pistons.
Pad springs have a little tab which helps hold the inner pad in position. This can get bent and hold the pad in the wrong position.
The silver pad clip in the calliper (which seats the tab) does not have a ridge in it on the front caliper. The rear clip does. Have you mixed up the rear and front pad clips ?
Have you got some grit between the rear of the pad and the silver backing plate.
Have you removed the bit of rag that dropped onto the calliper just before you set off for a ride.
(Do not ask me why I have asked that last one. I was young, I was foolish).
Have you bought Honda pads ? If not, are the new pads too thick ?
You fitted new pads so you pushed the pistons back.
Are either reservoirs now too full to release the pressure ? The centre piston is operated by the rear brake. Check both systems.
Any warning lights to indicate the ABS isn't working ? Might be the modulators not cycling / fuse blown / perhaps related to the point above. (I have known this on the 1100, not on the 1300 - but worth a mention).
Hope you get it sorted.