Hi All
Took my M20 on its first run on the road last week and it seems now that the oil pump doesn't seem to be doing much at all. I used to get quite a flow of oil coming into the oil tank but now only a few bubbles with lots of oil being pushed out the breather.
I have removed the oil pump and given it a good clean up but nothing really seems out of place, I will probably just re-assemble and see what happens.
My question: Is there anything anyone recommends I should do on re-assembly i.e greasing up certain bits, changing something factory fit for something better. The manual is pretty vague, i understand i should use a bit of gasket paste with the gasket but are the other faces on the oil pump metal to metal or should something be put between?
I am replacing all the oil and giving the oil tank a good clean out as there is a fair bit of debris in there. Also will probably change the oil filter in the tank for good measure.
Just would be interested to know if there was anything else anyone recommends doing as I want to do the job properly
email (option): martynhillyard@msn.com
Hi Martyn...You may have been a bit hasty removing the pump, although it does give you the opportunity to check it which is always worth doing...
The engine has a 'dry sump' oil system, meaning the crank case is cleared of oil after the engine has run for a while...
To achieve this one set of pump gears is wider than the other and consequently has a greater pumping capacity...The narrow gears are the 'feed' gears, the wider ones the 'return' gears...
When first started up there is commonly a constant flow of oil, particularly if the anti drain valve is leaking at all which allows oil to drain into the crankcase while the bike is standing...
After starting the return pump will gradually clear the excess oil and once the crankcases are empty (scavenged) the return flow to the oil tank will become an intermittent 'spit and bubble'...
This is normal and is the way the system functions...
As you have the pump out of the engine you can check it for free rotation...When fully assembled the pump should turn freely using just your fingers on the driving tang...If the pump is tight that must be rectified or the result will be a prematurely worn oil pump drive shaft...
There are no gaskets within the pump, only one between the pump and the crankcase...
The pump will then have to be lapped in, but that's another story...Ian
email (option): ian@wright52.plus.com
Sorry Martyn. I misread your original post...
If you have an oil return problem the first thing to check is the ball that is fitted in the small tubular extension of the pump base plate...
If that is stuck on its seat there will be little or no oil return to the tank and the excess in the crankcase will be ejected from the breather...You may notice some smoke from the exhaust as well...
It is possible that it was stuck and in removing and stripping the pump you may have inadvertently got it moving again..The ball doesn't tend to get stuck fast....The ball is captive within the tube but should be free to 'rattle about' when the oil is washed out..
There aren't generally any problems with the pump itself...In 40 or so years, for example, I have owned multiple BSA singles of this type and covered a lot of miles without ever experiencing pump problems..( I've done well over 100,000 miles on just one of them). As well as my own machines I've also rebuilt scores of engines for other people with the same result...
The only problems really are tightness of the pump caused by deterioration of the Mazac body castings and a stuck ball in the pick up pipe as described...and though it happens that isn't a frequent occurrence...
I would recommend you check the ball, flush the little pipe with some petrol, paraffin or similar...Then rebuild the pump and check it for tightness...If necessary rectify that and then refit it and test its operation again...Ian
email (option): ian@wright52.plus.com
Also, have a look at the Technical Section of the website: "Mounting the oil pump", it will make mounting a bit easier...