yes mechanical , i just disconnected steel line to carb and big rubber line to pump and left smaller hose on the pump . leak was at bolt holes and yes the arm was in place . because it can not ride over the cam . i will install new one today and see what happens . i disconnected feed line to carb. and no fuel reaching the carb . the pump worked fine , before removal , just leaked . i will have to retap holes , or drill out to bigger size and im not looking forward to that. it cranks fine and will start with gas poured in carb . , but will not stay running , due to no fuel reaching carb.