I used to be 115-120 kg (or around 250-260 pound), my first mod for my bike was also similar, but f running with a capital F. Not good for you, ***** your knees and joints and overall will hurt you more than probably doing nothing.
Get an exercise bike mate, 20 mins each day at a pace that makes you sweat. That was 1 year ago I got the exercise bike, I know weigh 85kg (185-190 pounds).
And funnily enough my bikes feel as if they have all got an extra 10HP
Never underestimate willpower............ willpower to move faster.........and not just on my bike