Hi all,

I've been recently refurbishing a 1973 RT3 that sat in heated storage for a few decades. 

I'm just wondering if a result of a bike that's sat is for the oil pump check valve to fail with oil leaking from tank into cylinder. 

Looking at the parts parts diagram, it looks like the valve is just a spring and ball. So, would that allow oil to pass from the tank into the cylinder? 

I definitely have fresh two stroke oil at the exhaust header. Is there anything else besides the check valve that would allow oil to pass from tank into cylinder?

Sometimes, people put 2 stroke oil down the spark plug hole when storing a bike for a while. This can end up in the exhaust if the piston is near bottom dead centre.

Check the seat in the oil pump where the ball sits in. Make sure it's clean, no dirt or crud in there and its not damaged. Use a magnifying glass and good light to check it out. If i store my bikes for any length of time i make sure the oil tank is low on oil. below the window low. 

Very common for oil to leak past over a long time and fill cases/pipe

If you don't want to make a mess you could remove the reed valve & suck it out as empty as possible with the piston above the inlet port, then run it up slowly until you feel it's back to normal. Empty the header pipe out or itll be spread right through on startup. Which eber way, it's going to smoke the village out for a bit. Hope you live out of town. The danger of kicking it hard to start with a belly full of oil is you could compromise the crank seals althought they're pretty big & strong on those & not easily dislodged. Oil pumps seem to slowly leak past over a long period of hibernating but it'll likely be ok with regular use. You'll soon know one way or the other.

Once had a check valve fail and empty the oil tank.  Once I rebuilt the pump and fitted a new ball and spring I have had no problems.  The cause was actually a tiny spec of dirt stuck in the valve.
Another cause is often a plugged tank vent, allowing pressure to build in the tank as the weather warms up and the bike is not ridden.  The pressure can lift the check valve ball off its seat and allow oil to pass.


Once bitten, twice shy.  When I lay the bikes up over winter, as well as draining the fuel and bagging the fuel tanks, I suck the oil out of the oil tanks, leaving just enough in to cover the bottom outlet.  I figure the reduced static pressure makes it less likely that the oil will leak past the valve and if it does, there is not enough to fill the crankcase.

I use this piece of kit.  It is invaluable for jobs such as this..

It's even funner in Canada, when one of your bikes starts to evacuate fluids in the dead of winter, and all you can do is put a pan under it like a diaper because it's -15C and there's no way you're touching metal parts in those conditions.