Rear brake Mod ?
 

Ok so, I've looked into the KB articles and searched the forum and I can't seem to find a solid list of direct fit/bolt on rear brake calipers. I think i saw somewhere that F4i rear calipers would fit but what years ? I'm looking to increase stopping power of the rear brake for as cheap as possible, any help would be greatly appreciated:cool:

Why do you feel the need for more rear brake? There's a reason there are no threads on it, for most people they are more than up to the task. Many riders use little if any rear brake, or lightly use it at best.

You would be better off replacing your front calipers with CBR600F4I and master cylinder.

My stocker locks up the tire anytime I want it to... if it's inadequate you may just need to make sure yours is working properly. Or not ride pulling a trailer and passenger.

Have you checked the fluid level, air in the system, or water in the lines?

A braided stainless steel brake line, EBC Kevlar pads and an annual bleeding and fluid change work for me.

The stock brake is more than adequate, and can lock the rear wheel at will... But it's also rather finicky on bleeding, as the last bit of the line can hold a bubble... Unbolt the caliper, and stick a piece of wood in place of the disc, and lift it to straighten the line, and open the bleed nipple... Should get the bubble out, and it's very likely this is your issue...

I definitely have something going on with this rear brake then because i'd have to stand on the rear brake lever to lock it up, not that i'm looking to lock it up haha, but going from my CBR to this bike REALLY leaves me wanting more rear brake power. I know, I know, many riders say "dont use rear brake" but i've always ridden using 70%front and 30% rear brake. I feel like it provides more stopping power without possibly skidding the front tire out (which has happened to me and thats enough to leave you needing a change of underwear) haha. Tweety, I believe you've probably hit the nail on the head because this rear brake feels like "marshmallow" almost the same as in a car if you were to have an air bubble in the brake lines. The previous owner installed upgraded front rotors and the front brakes are AWESOME for my riding style, I also have SS Braided lines installed and i've cleaned the rear rotor with a scotch pad so i know its not glazed... Thanks for the input everyone, I'll try bleeding the brakes at some point