My son has a pw80, which has comparable suspension, almost identical to ttr90. I read a Dec 02 post by a Dave Hamilton on mxamericaonline's forum about using a shock from a Madami Young Rider 10.10 Advanced 50cc minicross bike (yes- such a thing does exist, just took some searching). I spoke to a dealer in GA today, he got the specs: reservoir model, rebound and compression damping adjustable, 12" eye to eye, $139. There is a 10&3/4" model, no reservoir, probably cheaper. I will pull the stock shock tonite, measure and post my findings, and let y'all know how it works. BTW, for light trail use by my 60lb 6 yr old, the stock shock was passable once I rode it a lot and sacked out the stock spring. :) If the new shock is too stiff, I may need to ride it some too.