>I have the engine out and pistons/cylindars off. Any suggestions how to 
check
>the main bearings with our cracking open the case, I would like to avoid 
that
>if I can. I just want to put some new pistons and cylinders on.

>                           Tim (69 camper)

>    "TRUST YOURSELF, IT'S THE ONLY WAY TO FLY" Muir

Tim,
I don't know of a way to check the main bearings without splitting the case. 
 You
can check the rod bearings without opening it up( follow Muir's 
instructions).
How old is your engine?  Ever overheat?  Why are you replacing the p/c's?
Did you drop a valve?  My experience ('70 Bus)  was with an engine that ate
 number 3due to detonation caused by overheating.  I replaced the
p/c's and heads.  The rod bearings checked out ok.  After reassembling, the 
engine
would seize after driving about 3 miles and would not turn over until it 
cooled
back down.  I pulled the engine and split the case.  Main and rod bearings
were toast.  They were marginal at best and the added compression of a new
top end sent them over the edge.  If you have a lot of miles on the engine
or any reason to suspect the bearings, go ahead and do them now and save
the hassle of pulling the engine again.

Charles Armstrong
'70 Bus
'69 BMW 1600-2