engine case change at the end of the time frame for this section

I have this custom chassis with a 430 engine in it. I bought a new set of friction plates for it and it didn't last one day digging trenches and the like. I had to take the chain off to push it. Well now I have decided it must be that bearing near the sprocket. I have discovered that it will not be possible to pull the bearing out from the outside like has been discussed here within the last half a year. I also notice the same thing happened on the four stroke version.

I am hoping someone might know if this was a weight saving or cost cutting or done for some engineering reason. I have welded on this case and the weld looks like the magnesium has less impurities than some of the other stuff I have welded. Any idea if a different supplier made these which I suspect are out there as replacement cases if you can find a replacement case. The parts sheet for a 1999 four stroke looks very similar as well.

I grafted two images from the same parts pdf file to get this picture.

My 87 430 cases are the same, bearing only goes out toward the inside. I read somewere? that they redesigned the cases at the rear area for more strength when they went to the single shock. Looking at the differences I would believe the later cases would leak less at the output bearing because of the more shielded design.

I guess it is a blessing in disguise this time. The seal behind the electrics was in crooked, the bore for the clutch arm is real worn and a lot of dirt has got into that bearing. Sitll I have to wonder as the dealer which sold the bike I got this engine from changed that bearing near the sprocket as a matter of preventative maintance for his customers. At least prior.

Edit/add
Well it appears that bearing at the sprocket kind of cracked all the way around in the groove the balls ride in and the inner protion sure would have been easier to get out with the older design. I warmed it turned it over and hit the inner race with a wooden drift and it came out but upon turning it over not all of it came out. That type of failure isn't real good for the bearing pocket either.

Fran