CRAFTMANS RIDING MOWER,917.276040,25HP KOHLER 48"DECK?

Starter will not engage. When jump across starter mower will start. When release brake pedal mower will die! unhooked pedal safety switch tractor will move forward and backwards,(seat safety switch also unhooked)but when engage mower pto switch mower will die. unhooked pto clutch beyond switch mower still dies when switch is engaged .Replaced pto switch still same problem. old switch did look somewhat melted. hooked seat safety switch back up still same problem .
Anyone got any idea's ?
dheh83@yahoo.com