Do it mate! I changed from a 'Storm to an SP1....hellish good bikes. They have very little in common with the 'Storms... more power (mine had 130 RWHP), far better brakes, much sharper handling. They are not as comfortable...lots of weight on your wrists, and you are very hunched over the front wheel.
Make sure to get a Power Commander if you can. The SP1s are notoriously snatchy low down...a PC will transform it. Do the flapper mod, and a decent map will smooth out the mid-range as well.
The suspension is leagues better than the 'Storm...though the rear shock is over-sprung (unless you are a big lad). penske shocks are recommended, though £180 spent at K-Tech will have it re-valved and re-sprung to your weight....makes a hell of a difference. The front forks are really good....spend a bit of time setting the suspension to your weight and it will make a big difference. The adjustments clickers make a big difference, and a click or two is very noticeable.
The brakes are miles better than the 'Storms, and are comparable to modern radial brakes (especially if they have been looked after, and have fresh fluid). I stuck a radial M/C on mine....gave it a bit more sensitivity and power.
This was my old one....still miss it

(any excuse to picture whore

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