i bought a new in box ST 2500 a few years back , the old owner added a backplate, because he apparently lost the orig backplate , he included the radial mount, which i'm not going to use. because i'm going with a standard mount.

the prob is that the backplate is for something else and hits the conecting rod, because its too long .

i went to tower hob and the part number checks out , but its the wrong part.

thanks

If the bolt holes for the rear cover fit the bolt holes in the case, then you have the correct rear cover. SuperTigre only made one kind of rear cover for the S-2000/2500 egnines. You may need to check to be sure the crank shaft is fully-seated in the bearings, or also that the rear bearing is fully-seated in the front case.

since the engine is new , the bearings should be seated, but there is play where the con rod
is conected to the crankshaft, probably about .020 front to back , with no side play

If you have no propeller mounted, and the drive washer is loose, then it's normal for the crank to slide rearward enough to strike the rear cover. If the prop is mounted, remove it and the drive washer, pull the crank fully-forward, and reinstall the drive washer and prop. It should cure your difficulty.

thanks , tightening the prop took up the play