centering on bed

Hi I am new to 3d printing, I have a prusa clone that worked fine to start, then I started having problems with the extruder plugging constantly, I purchased an aero titan extruder and hot end, installed it on new mount with nozzle as close as I could to the old nozzle position, the printer homes properly but I cannot get it to center for the print, when I hit print it moves to approx. 10mm beyond center on the x and 20mm to the rear of center on the y. I have spent hours trying to rectify. I have marlin 1.0 firmware
Any help would be much appreciated.
Terry

You need to re setup X0

Home X, where is the nozel? I suspect its now at -10

Set this in configuration.h


// Travel limits (mm) after homing, corresponding to endstop positions.
#define X_MIN_POS -10
#define Y_MIN_POS 0
#define Z_MIN_POS 0
#define X_MAX_POS X_BED_SIZE
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 200

Edited 1 time(s). Last edit at 02/03/2018 07:12PM by Dust.

Thanks very much for the info, will give it a try.
Terry