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Most oil pumps are setup with the
throttle wide open or closed and simply lining up 2 marks. The RD500 pump
has an extra feature....the YPVS
system interferes with it. I use the method below to set mine and have not had any
trouble
with rear cylinder seizes since.
Turn your ignition on and let the YPVS whirring finish. The mark on the edge
of the hole in the lever should line up with the line scribed on the ally lug
underneath the lever ( line is visible through the hole). That is all you have
to do according to the manual.
When you have checked this and got it spot on try this:-
1) Turn the ignition off
2) Practice a few times turning it on and trying to stop the YPVS cycle halfway
through. There is a delay in the cycle at the point you are looking for so its
not that difficult. What you are trying to do is turn the ignition back off
again when the pump lever is in the closed position. ie lying back against the
frame cross tube. (This is the position the lever will be in when you start the
engine).
3) Rotate the throttle ever so slightly. You now need to observe 3 things
simultaneously. The 2 carb throttle 'drums and the oil pump lever. They should
all start to move at exactly the same time. You could just check it against one
carb but looking at both gives you an idea as to the state of the carb balance
too.
If the oil pump lever moves first you will have too much oil and possibly foul
plugs easy when pootling about, plus you could also have a pretty lumpy
4-strokey motor at low revs.
If the carbs move first its possible to run with no oil at all on small throttle
openings. The trouble with an RD500 is you can cruise all day at 80-90 mph in
top gear (5000-6000 revs) with the throttle practically closed. You definately
don't want the oil pump to be closed at 6000rpm...
You need to juggle around with the adjusters until you achieve all of the
conditions I have mentioned. If you do and you use a good oil you should never
seize a rear cylinder again - well if everything is functioning normally.
You can make a quick check when the bike is ticking over, and it may be easier
to detect what is going on this way. Slowly turn the throttle a very small
amount - When the revs start to rise your pump should move. The revs rise at
exactly the same time as the oil pump lever moves.
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