On my 1985 K100 RS, is it possible to remove and replace the lower crank case with the engine still in the frame?

I have stripped the bike from the back to the gearbox and I'm now at the point of beginning to remove the clutch.

According to the wizard AI the lower crankcase cannot be removed without first removing the engine from the frame. Is this correct ?

I have the bike on its side and have the opportunity to remove the clutch and then the lower crankcase however I am worried about "splitting the engine" as the AI says and having to put it back together again "in a balanced manner".

All of this work is necessary as a result of a bolt on the timing cover breaking inside, and falling into the sump... at least this is what I think happened.  When I started the bike after replacing the cover gasket there was an almighty bang followed by an oil leak of equal and continuous pressure around the edge of the lower crankcase where it mates with the upper part of the engine.

 I have a replacement lower crankcase housing, although it may just be the seal that has gone as a result of impact from the sheared cover bolt, from what I have read in my searches on here and elsewhere, the crankcase could be cracked so I have the replacement lower crankcase here in case it is.

This is the first time I have done this in 25 years of owning K bikes.

So to sum up my question ... as I need to remove the lower crankcase to inspect, do I need to remove the engine to do this or can it be done with the bike supported upright or on its side?

Any advice gratefully received.

I had my rear wheel widened by Kosman but kept the 17 inch size.  Welds look the same as yours.
Luftmeister took stock cams, welded material on and machined down to get more lift/duration.  The ones I have seen were quite evidently modified.
That air filter mod does away with the stock intake that avoids engine/radiator heat.  I doubt that it helps much.
I also had a Koni shock once upon a time.  It was fine until I sprang to an Ohlins.

Frank

Wondering if a previous owner put some of the Luftmeister parts in to my FYK. It's got the nicely welded 18 inch rear wheel, airbox mod that comes out in to a single K&N air filter. Pulls strong from 4k RPM up until I don't know how high (I don't run all the way to redline). Exhaust header is factory, but it's got a Supertrapp muffler on it. Semi-related, it has a Koni rear shock.
Something new to me, was to see the 100k Mile BMW medallion on the Coil cover.
I bought it from a guy, who bought it from a friend that got it from an estate.
No, I don't really want to pull the cams to measure duration and lift.
Some photos attached in case anyone knows the specific bike.

Actually: according to Muphy once you return the seals your current ones WILL fail...

If it were me, I'd keep the seals as long as you already have them. You most likely will need them at some point.
Murphy would say that if you send the seals back, then when you do need them, you won't be able to find them....

Just food for thought.....