As everyone said, fork leakage issues, one fix was to combine 3 single lip seals in place of one single seal, rough the slides with 600+ emery cloth/crocus pape, seems like a bit better for oil to stick to fork and seal rather then pass by, note the forks are different, one compression, other rebound.
Electrics can fail, found that cheapest & most reliable was to have motor rewind shop replace, bud with 1 yr newer model had received from dealer a faulty unit, found this out by resistance measurements & replacing his with my unit.
Watch out for the mystery oil drain plug, mistaking the shift retainer/whatever bolt may result in teardown exercise of Rotax motor.
Purple 1989's? where milder than the green 1990? "hot rod", something to do with the rotary valve slot size I/P. If ever submerged hot/running the valve would warp & seals could displace, this problem was rectified in our area as that we no longer allowed in streams were fish ran, and typically any water over the rim disappeared in sections once bikes became pricey.
Rest of the bike can be repaired with some resourcefulness, enjoy the power & the sound of the straight cut gearbox(never tired of this).
To bad Aprilia dropped the trials line after the world win, but was more likely heavily biased by Rotax(Bombardiar) not allowing changes to there tried & true design.
Many various parts are likely about with ex-dealers, plastics could be rarest, if price was cheap & you have basic maintenace knowledge great entry bike.