On my '84 I used to get lifters that would not pump up.  Try Marvel Mystery
Oil at your next oil change.  (I know what you youngsters are thinking, but
this stuff has been around since the '20s)  Substitute a quart for a quart
of oil.  Check oil with every fill up, it's a light solvent oil that can be
consumed fairly quickly in our loose engines.  Top up with that quart of
motor oil you didn't use.   BTW, don't be tempted to drink it or leave it
around where children can get at it.  It contains methyl
salicylate--wintergreen--and smells like candy (or a flavored vodka!).  It's
also bright red with a cool art deco label to boot.  Actually, now that I
think of it I've been wanting to order this tin sign for my garage:
http://tinyurl.com/cff5f8g .

Worked well for me.  I think varnish build up in the oil hole in the side of
the lifter coupled with low oil pressure is the culprit.  I also would not
run anything less than a 15w-something oil.  5w & 10w are physically too
thin for the WBX to build adequate oil pressure IMHO.  The bearing
clearances expand a lot when these engines get hot and this reduces oil
pressure.

From my past history on this and other lists since 1997, it seems that
rebuilt WBX engines do not last as long as the factory original, no matter
how carefully they are done.  For example, lifter bores cannot be
reconditioned and have the wear of the total miles on the case.  Granted
they don't wear much, but this is another reason for more viscous oil.
Things haven't been the same for old engines since zinc was removed from
motor oil,

Start saving for your engine conversion of choice.  You probably have
considerable time left on this engine, but I personally wouldn't rebuild it
again.  Also, I'm concerned about your comment that there was a gap between
the valve and the rocker arm.  This could be excessive cam lobe or lifter
wear.  You will know because you will soon have a dead cylinder if it is.

Good luck!

Stuart
'85 Westy