Hi , What exactly are the differences between these two engines mechanically? Things I'm aware of are the cams and I can see no external oil feed lines from crankcase to cyl. (how does ie allow for cooling then?) Also I believe internal gear ratios are different (2:1 on carby and 1.84:1 on the ie)) ...resulting in a 15/37 final drive on carby and 14.40 on the ie. But are heads and valves the same? what parts are interchangeable. Swinging arm pivot wider acroos cases? I've got a cosmetically tired '93 ss engine (probably with the 'fragile head studs?) and looking at rebuild and tune up (head work and 39mm FCRs) but have also picked up a 16k miles, 2002 ie engine . (engine and donor bike below) Just wondering whether to rebuild or just swap. Your collective wisdom and experience please!