The 681 I ran with stock springs was way to easy to hit the limit travel and actually feel more vibrations. I never got to run one with the 7900 springs but the 7900s are much stiffer feeling which I like. They weigh a little more than the 70-81cc class but the power is nice.
It looks pretty good in the picture. I would imagine you can get it back going pretty easily. Hopefully they didn't leave it half full of ethanol gas so you have to go through the whole fuel system too.