TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: Anything2stroke on June 07, 2017, 07:14:30 PM
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I bought some new sprockets and it doesn't clear the stock case saver
What do you guys suggest for a case saver?
Gears are 15 tooth and 36 tooth.
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Most all the aftermarket case savers will clear a 15 with 520 chain.
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I know a Duncan clears. Legacy and the Nac's won't even clear a 14. I think the Baldwin I had cleared a 14 but I can't remember if I tried a 15T on it.
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I would get a UPP case saver, grab your Dremel and carve it out until it fits. For looks/aesthetics an aluminum saver looks nice but they won't provide the protection of a poly unit.
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I had to dremal my poly casesaver to clear ESR stator cover.
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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
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Dang 1mm is tight! At what angle do you want that clearance to be in effect? Obviously you wouldn't want it that tight for the entire 180° so let's say based on 90° vertical from the counter shaft centerline would you want to have that 1mm by say 45° before parallel & than open back up again at 45° past parallel?
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The point of entrance and exit depends upon the sprocket diameters and distance between the centerline of both sprockets and the amount of ware on your sprocket and chain.
I attempt to maintain approximately 1 mm clearance from the chain tangency points on the top and bottom of the countershaft sprocket. The number of degrees between these two tangency points will never be more than 180 degrees. The basic concept is than the chain MUST stay tightly wrapped around the CS sprocket for a case saver to do what it is suppose to do. One design deficiency I see on many of the case savers is that they need more chain direction control on the bottom of the countershaft sprocket to guide the chain alone the straight line between the chain tangency points on the bottoms of the two sprockets when the suspension is topped out.
There is not a need for a case saver as long as the chain stays on the sprockets. If a chain breaks, the chain should feed into the top of the CS sprocket with the case saver keeping the chain fully meshed with the CS sprocket until the last link exits the CS sprocket and guides the chain away from the shift shaft, frame or any other obstacle as the chain exits the bottom of the CS sprocket.
If a chain is derailed from the rear sprocket and there is not any bent kinks in the chain or there is not any broken teeth on the CS sprocket, a case saver should allow the chain to stay on the CS sprocket and continue to run long enough to saw the rear axle in half. ;D