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Re: 1939 Matchless G3 No Oil Pressure

Before oil returns to the top of the oil tank as far as i can remember it has to fill the filter tube first. These pumps pump slow with little volume, so it would be a while before oil is seen at the return pipe in the tank. Oil needs to be in the bottom of the crankcase for the pump to pick it up. You have said the pump is rotating and moving backwards and forwards. Try priming the crankcase and taking the return pipe off the bottom of the oil tank and watching the top of the pipe as it only has to fill it before you see any return oil.

Re: 1939 Matchless G3 No Oil Pressure

couple of things you could try and check. make sure the pump gear teeth are ok, with the front oil plate the rocker pipe bolts to removed, turn the engine and check that the pump moves or Oscillating all the way to the edge of the engine case and goes back.
put oil in the return outlet on the oil, i use a triggered oil can. check the oil filer maybe clean out in petrol.
another thing, with the oil drain bolt removed, inside the engine directly above the filler hole theres a small hole in the casting, check to se if its clear with a bit of wire or blow it through with air gun. normally if this is blocked the engine would fill with oil as its the scavenge pipe if you like and also part of the oil return.
hope this helps

thanks, barry

Re: 1939 Matchless G3 No Oil Pressure

Some additional items to check.
If the pump guide pin has any ware at the point that it engages with the pump then oil will not get up to the head.if there is any flat spot on th3 pin then replace it.
Make sure you have the correct reciprocating pump fitted and not the later pump as they are not interchangeable
Make sure the hole in the front end plate allowing the oil to be pumped up to the head is not blocked and the the gasket paper does not cover it over.
Make sure there is oil in the sump by squirting oil down the pushrod tubes
Prime the system by removing the cap over the filter and filling the tube with oil. Also use an oil can to back fill the return pipe by squirting oil down the return hole in the tank.
Make sure you do not have the return and feed pipe the wrong way around.
I always get on my bikes and ride them around the block before I check that oil is returning to the tank as it takes ages.

Let us know how you get on. JT

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