610 upper chain roller lifespan

1996 WXC 610.

What kind of lifespan is normal for the upper chain roller?

So far, I have had 3 completely fall apart: the one that was on it when I purchased it lasted 2 rides, a new OEM replacement lasted about 12 rides, and a spare YZ450 roller only lasted 1 ride.

I had a 96 610 and never had one fall apart. I was also never that high in the air on it.

Well, like the last thread I started, it soon turns into another issue... I changed the oil today and stuck on the end of the magnet was a piece of what I think is 6th gear.



The gear in the picture is just one on ebay I am using as a reference point. Sure looks like one of those side lobes.

Does anyone know how critical those are? Would it be ok, with just the remaining 3? I’ve never used 6th gear before, if that is indeed where it came from.

Not sure what would have caused it to break, I normally ride pretty much in 3rd gear about 90% of the time.

There are dogs on other gears as well, they engage the gear next to them.