Just say no to Chinese bearings?

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So to add a twist to the conversation. One of my test saws came back from full time logging work.....with an air leak under the clutch to the point a shot of brake clean just instantly stopped the saw when sprayed there. It was a HyWay 52mm popup on AM cases with an OEM crank and OEM XT carb ...muffler mod. No base gasket. Basically ALL AGAINST the ONLINE expert grain. Had the Chinese bearings and seals that came with the AM cases..did a video a while back documenting that saws birth. Strong runner..until it started going lean. Had to use a plastic hammer to bust that 1184 seal...like usual. NO leaks there!



So folks....it wasn't the bearing that failed. Bearing is just as smooth as it always was and no discernible change in clearances. Crank end was wobbling in there when I pulled off the clutch and oil pump..was pretty certain it was a bearing! And BTW the top end survived as well....so caught it before it went catastrophic... :)



It was the bearing pocket that opened up to the point that bearing slid out with my finger on tear down. Didn't spin or anything like that....just opened up! Case must be soft. It's in the scrap heap now! Building it back with ANOTHER set of AM cases to see if this is a trend. Going to re-use that same Chinese bearing in the second iteration. ( Video to come with the analysis and build in a week or three. )
 
So to add a twist to the conversation. One of my test saws came back from full time logging work.....with an air leak under the clutch to the point a shot of brake clean just instantly stopped the saw when sprayed there. It was a HyWay 52mm popup on AM cases with an OEM crank and OEM XT carb ...muffler mod. No base gasket. Basically ALL AGAINST the ONLINE expert grain. Had the Chinese bearings and seals that came with the AM cases..did a video a while back documenting that saws birth. Strong runner..until it started going lean. Had to use a plastic hammer to bust that 1184 seal...like usual. NO leaks there!



So folks....it wasn't the bearing that failed. Bearing is just as smooth as it always was and no discernible change in clearances. Crank end was wobbling in there when I pulled off the clutch and oil pump..was pretty certain it was a bearing! And BTW the top end survived as well....so caught it before it went catastrophic... :)



It was the bearing pocket that opened up to the point that bearing slid out with my finger on tear down. Didn't spin or anything like that....just opened up! Case must be soft. It's in the scrap heap now! Building it back with ANOTHER set of AM cases to see if this is a trend. Going to re-use that same Chinese bearing in the second iteration. ( Video to come with the analysis and build in a week or three. )
In an interference fit like that couldn't it be either part? Since this is a thread about bearings, what if the outer race OD was slightly under? It's not on my bench to check, just asking questions...
 
In an interference fit like that couldn't it be either part? Since this is a thread about bearings, what if the outer race OD was slightly under? It's not on my bench to check, just asking questions...

Interesting to me is even though that pocket was as open as it was, that bearing did not spin in there. A testament to the bearing actually. Outer diameter is fine on that bearing and when the saw went together the interference fit was as it should be and I'm checking the replacement AM case to be certain and will put together "2.0". Understand all who read these things that it takes more than one even two incidences to be a trend. SO if the second set of cases fail in the same way further analysis might make sense. Also understand the stresses put on that case will differ than most here reading and using this as information. That saw has a much higher than stock compression ratio, more "pop" every stroke hammering the bottom end. The 52 mm piston has a different weight than the OEM piston that was originally attached to that crank...might induce more vibration there. ( Any one ever use an air hammer to push things around? ) And with it's particular configuration with the carb/muffler mod and a few other things, it likes to be at a higher RPM in the cut than the typical stocker., In the environment it was tested that saw was brutalized as the fellow only cuts big hard wood with a 24inch bar "Game of logging" bore cut style. ( I am positive that GOL fellow has a stake in some bar manufacturing company.) But the vibrations from that op also have to be dealt with by the PTO side bearings as well...through the sprocket driving that chain. My hunch is the 6 months that saw was used daily in that operation put more harsh time on that saw then most typical hobby type or firewood type for an entire life time. The intense bore cutting and long bucking cuts that have a bore cut component as well have to stress the saw more than simply blocking firewood or making cookies.

SO suggestion? Wait and see 2.0 and while that is happening we all can collect experiences....if a few more show up with the same failure THEN we have a trend, not just because of mine. My hunch? Those cases and bearings are just fine for saws in stock or close to stock configuration. AND ALL 372's with those 6202 bearings are pushing the edge when more compression, heat, RPM.s, vibration due to unbalances components (ie. miss matched crank/pistons ) and power are pumped into the equation. And while it's possible OEM cases have a better material, that design was on the edge day one. Evidence? Don't get me started, I'll just get in trouble. But the bottom line for me is in the theoretical world that might matter, in the real world, being smart with the build yield's a saw with a lot of power for the weight that is a blast to use. Part 2? Careful what you wish for when companies prioritize weight for the spec sheet vs. durability.
 
Interesting to me is even though that pocket was as open as it was, that bearing did not spin in there. A testament to the bearing actually. Outer diameter is fine on that bearing and when the saw went together the interference fit was as it should be and I'm checking the replacement AM case to be certain and will put together "2.0". Understand all who read these things that it takes more than one even two incidences to be a trend. SO if the second set of cases fail in the same way further analysis might make sense. Also understand the stresses put on that case will differ than most here reading and using this as information. That saw has a much higher than stock compression ratio, more "pop" every stroke hammering the bottom end. The 52 mm piston has a different weight than the OEM piston that was originally attached to that crank...might induce more vibration there. ( Any one ever use an air hammer to push things around? ) And with it's particular configuration with the carb/muffler mod and a few other things, it likes to be at a higher RPM in the cut than the typical stocker., In the environment it was tested that saw was brutalized as the fellow only cuts big hard wood with a 24inch bar "Game of logging" bore cut style. ( I am positive that GOL fellow has a stake in some bar manufacturing company.) But the vibrations from that op also have to be dealt with by the PTO side bearings as well...through the sprocket driving that chain. My hunch is the 6 months that saw was used daily in that operation put more harsh time on that saw then most typical hobby type or firewood type for an entire life time. The intense bore cutting and long bucking cuts that have a bore cut component as well have to stress the saw more than simply blocking firewood or making cookies.

SO suggestion? Wait and see 2.0 and while that is happening we all can collect experiences....if a few more show up with the same failure THEN we have a trend, not just because of mine. My hunch? Those cases and bearings are just fine for saws in stock or close to stock configuration. AND ALL 372's with those 6202 bearings are pushing the edge when more compression, heat, RPM.s, vibration due to unbalances components (ie. miss matched crank/pistons ) and power are pumped into the equation. And while it's possible OEM cases have a better material, that design was on the edge day one. Evidence? Don't get me started, I'll just get in trouble. But the bottom line for me is in the theoretical world that might matter, in the real world, being smart with the build yield's a saw with a lot of power for the weight that is a blast to use. Part 2? Careful what you wish for when companies prioritize weight for the spec sheet vs. durability.
Referring to Stihl's new offerings?
 
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