I saw this old thread and it reminded me of a recent conversation I had with a customer that had a chain derailment that resulted in destroyed cases. It had a beautiful billet heavy duty case saver that had too much clearance between the outside of the chain where it wraps around the countershaft sprocket. It looked like the case saver was made for a countershaft sprocket one tooth larger than what the customer was using.
I have repaired a lot of broken case savers mounts on the cases and bent shift shafts on the 250s since these quads were new. The majority of the damage could have been prevented if the correct case saver had been used.
The brand of the case saver is not as important as the way the case saver fits your combination of chain and sprocket. Case savers are not universal in the sense that one case saver will keep the chain on the counter shaft sprocket in the event the chain derails from the rear sprocket, with any type of chain, on any countershaft sprocket of any tooth count.
The purpose of a properly designed case saver is to keep the chain on the sprocket until you get stopped and correct the reason the the chain derailment. The case saver must guide and feed the chain, link by link, into the countershaft sprocket. The case saver must keep the chain on the sprocket continuously as the chain wraps around approximately 180 degrees of countershaft sprocket. The case saver must direct the exit of the chain from the countershaft sprocket in a manner that clears the shift shaft and will prevent the chain from "bunching up" in the area before the chain gets to the shiftshaft. "Bunching up" or "wadding up" is what destroys the shift shaft, breaks cases and sometimes bends or breaks counter shafts.
A properly designed case saver can only offer protection when used with a particular tooth count counter countershaft sprocket and type of chain. Some chains are a little "thicker" and many of the aftermarket case savers are not machined properly to offer close fitment next the rollers in the chain. The close fitment (1 mm or less) of the case saver next to the rollers of the chain, will offer the most protection in the event of a chain derailment