Chainsaw Repair

What is the difference in these 2 651 then the newer 651 now days in silver and red.

This is copy and pasted info I have found on the other 2 so far.

 Solo 651 vs 651SP

    The major difference apart from the red top and some other minor differences is this:

    1) 651 has a totally different piston (short and cropped skirt) same jug
    2) the 651 has a electronically controlled variable advance ignition module (as opposed to the standard electronic ignition on the 651SP
    3) The 651 has a rim drive as opposed to a spur sprocket on the 651SP
    4) The 651 has a magnesium sprocket cover and different chain catch arrangement- the 651 has a composite side cover.