Dude, did you not get the step by step instructions WITH pics I sent you on the Busa install? Follow those directions and if you don't like it, no harm -no foul, then a shock that is properly designed for the Bandit can be installed. It will raise the rear quite a bit, over 1.25". It will steer quicker and might feel twitchy in the corners. May need lowering links to bring the back to stock height.
Pros-Cheap, adjustments are plenty. Some heavy weight guys love it. Yes better than the stock Bandit shock but what isn't.
Cons-spring weight for a heavier bike and has been known to be harsh with lighter riders. Requires minor grinding of shock and mount. For me, suspension always wanted to rebound too fast on hard deceleration no matter what setting.
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A 89-92 Gixxer shock will bolt right in-no modifications. Depending on the model (GSXR750 or 1100) it came from will determine the spring rate. Both of which are designed for a much lighter bike with a lighter rider. Raises the rear about an inch. You will have an piggyback cylinder to mount under the seat or on the side rail.
Plus side-cheap to try and can be recharged and resprung for your weight(although it will cost nearly what a proper shock does)
Downside- those year gixxers are already worn out (15+yr old shock), spring weight designed for a 400lb bike instead of 540lb bike.
I say this as a fellow Bandit rider whom himself has tried everyone of these 'alternatives' and ended up spending more time AND money than just buying the proper shock. I now have the proper shock and thus is why I lecture. I did cheap out and go with the $415 Heavy Duty version of the Progressive instead of a $600 Penske. It can be revalved and rebuilt. It also has some residual resale if I get rid of the Bandit. I know, blasphemy.
ALSO VERY IMPORTANT
You will find that if one these shocks work for you...it will show any and all downsides of how crappy the front suspension is! Be prepared to replace that as well, either new springs ($56) or better fork oil.