Double gasket blow-out

A couple years back I paid someone to assemble a CB450 engine for me. It didn't cost much and turns out I got what I paid for. The engine blew a tiny bit of oil from the front of the head gasket since day one. Not much, like a well cared for brit. Wiping the oil off after every ride kept the ride shiny and rust free. I put a beating on that bike over the past two years, the last couple rides ended with my engine smoking, from the outside! The leak opened up more and more till my engine became externally oil cooled. Which is fine, bike still made it home. (thanks Mr.Honda!) Anyway, my last couple jaunts into the catskills really pushed the limits of those gaskets, dropping gears into corners, engine braking and bad seals don't mix. I knew this was it, made it home and put the bike up on the table to prep for winter surgery.

I couldn't make it to the bike immediately (other projects) and when I finally got to the 450 to give it a once over I found that a LOT of oil had drained out through the shifter gasket(?wtf?)...?

So, it seems I blew it in two spots. I have already started to get it together for a top-end overhaul. 450 cylinders have a tendancy to warp from heat, I'm betting that is part of the problem.

I have seen the clutch pushrod gaskets go, never a shifter (again?) gasket. I was hoping to avoid craking the bottom-end...

Sorry about mis-labeling the shifter gasket, I'm too tired to get it straight.

Has anyone ever replaced one of these WITHOUT cracking open the infernal black box?

BORN TO LURK, FORCED TO WORK.
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