Its been a long time since i had one out of bike but maybe its for a klx110? I remember reading there was one for honda 50 style engines but it was extremely rare, so if it is one you might have trouble finding someone to identify it.

 

its a magura klx110 slave. as you already noted its not a direct fit. with some work you can manage to retro fit it. unfortunately i never done one for a trx 90 so i wont be able to say exactly what needs to be done in order to make it work.

 

It will be highly dependent on how much throw you can get out of it, but it should be a relatively simple mod if it actually fits behind the clutch cover.

 

I think I measured the throw to be about 6mm. It does fit in there, with room to spare. It would need a bushing to fit properly in the bearing...and to make up about 10mm to fit tight against the clutch. I'm sure it could be made to work, but I figure I'd need at least 3 custom pieces turned, and then it will still stick out a little too far on the outside of the motor.

 

I was intrigued with the concept of a hydraulic clutch actuator yrs ago but every one I have seen stick out from the engine case enough to be a problem for me.

 

Looks like a pps clutch that's good stuff sticks out far but works great