Bigger piston M/C ?

On my 77' KZ1000A upgraded to dual disc front brakes and single piston calipers from an LTD. I'm using a 5/8" piston M/C and it seems the brake lever pulls in more than 1/2 way for full braking. Should I have with a larger piston M/C since I upgraded to dual disc brakes ?

I'm just comparing the brake lever travel distance with my 75' Goldwing and 74' CB 750 K4 which "both" have less brake lever travel.

To much travel in the brake leveler is a sign of air in the break line(s) or caliper(s)
1/2 mc piston = single disc, 5/8 mc piston = dual disc
If you use rubber break lines go and buy modern steel flex lines and do a correct bleeding.

rubber brake line new



rubber brake line old



steel flex brake line

I haven't modified a KZ yet but I used a 14mm/ 9/16 M/C on my 79 gl1000 It had more travel but excellent lever control. I also changed a cb750F from single disc to double with a stock m/c, same deal more travel but it worked great.
Does your master cylinder have any form of lever adjustment? I've also left rubber bands on the lever overnight to let the air bubbles compress and float up to the top.
Good Luck, D.

5/8" if the proper size for a dual disc bike.

Did you pull the pistons out of the LTD calipers and make sure they are clean? If you rebuild them be sure to use OEM parts, not sucky K&L parts. Binding caliper pistons can lead to the pistons not moving close enough to the disc and that causes spongy lever feel.