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Oil Fillers



The Oilhead oil fillers were all plastic bayonet type.   They would all hold
if you were careful to keep them clean.  That is, until you got out on the
good roads and started wringing out the engines at higher RPMs and using a
bunch of engine braking.   Under those conditions, the internal pressure and
vacuum inside the engine was just too much for these loose-fit devices and
you got oil coming out of the plug.at least I did with both my '99 1100RT
and my '04 1150RT.   


In both cases, I replaced the stock plastic bayonet filler with a metal
screw-down type and in both cases the problem was fixed for good.   The
tamper proof feature is an extra benefit, but not the primary benefit for


Warning:  Do not attempt to mount one of the metal screw-down sleeves in the
valve cover without removing the valve cover first.   A friend dropped one
of the tiny set screws down in the engine trying to do this (right before a
big trip, of course) and had to pay someone to take his engine apart to find
the screw before he could start the bike.  When the tech finally found the
screw, it was between links in the timing chain.   It probably would have
caused huge damage had he decided to ignore it.  I came over to his house
night before this trip and we looked with bore scopes and tried grabbers and
an illuminated magnet on a bendy pole.  We drained all the oil.   Nothing
worked.   It required removing the cylinders to find it.  Just don't go
there.   Remove the valve cover. 


When I got my '05 1200RT, it came with a plastic screw-down filler.  I've
had no problems with that design.   Works great no matter how hard I flog
the bike.  It's also tamper proof with that strange plastic triangular
wrench thing.   It will leak a bit if you don't dry the gasket off before
you screw it in, but if you do, and then turn it down tight, it holds in all


Viton is nice stuff.  The "standard rubber" referred to in one of the posts
is Buna-N.  It's fine too, but it doesn't last as long as Viton.   Buna does
swell a little in the presence of oil, but it's not detrimental to sealing.
A Buna-n O-ring will last a couple years and they can usually be found at
hardware stores.