I installed a ‘lift kit’ on my ‘75 ST90 a few months back. Best upgrade on this bike that I’ve ever done. Installed in about 30 minutes and what a difference it made. No more bottoming out, raised seat height about 3” and made it a lot more comfortable to ride for a tall guy. My ST is an unrestored original with 1500 miles, 500 of which I personally put on it. It’s a rider, not a restored bike so I have no qualms with non original parts. If you have suspension issues with one I highly recommend this upgrade.