Bike is 1959 Model 50. I currently have the chain case off addressing problems with the alternator - ref. earlier messages. While I've been doing this I've noticed oil leaking out of a breather tube. The tube comes from a casting/cage that bolts to the crankcase on the drive side.
Due to worries about the ball valve on the oil supply from the tank (pump wasn't overcoming the spring and oil supply restricted) to the pump I've removed it. As a result, and as expected, wet sumping has ocurred. However, the oil in the sump is dripping out continuously from the above mentioned breather. Over a week the whole oil tank has emptied. How can this happen ? Is it normal ? Is something wrong ? I am assuming that, with the chain case cover on, this oil, rather than/or as well as, dripping on to the road it could overflow into the chain case.
Any ideas as to how to address this, other than re-instating the ball valve.
Mike Haworth
If we think about it, whit…
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Previously michael_sulliva…
Previously michael_sullivan wrote:
If we think about it, whith the crankshaft installed in the crankcase, there is very little room. So, if the oil tank is emptying into the crankcase through the oil pump gears it will not take too much oil to fill it up. Once the crankcase gets half full the oil will find its way out to the breather on the left hand side.
Some people fit spring loaded check valves in the supply line to the oil pump but they run the risk of the valve failing and making the engine run dry.
Other than replacing the oil pump you can just run the engine every 3-4 days or baring that just drain the sump before you ride it.
Mike
Thanks for reply. What purpose does this breather fulfil ? Would it be reasonable to seal it off in order to stop this oil wastage when left for long periods ? There is another crancase breather, much more substantial with a copper pipe, coming out above it, isn't this sufficient ?
Mike Haworth
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You need the breather. If…
You need the breather. If you think about it, every time the piston goes down from TDC to BDC it reduces the space in the crankcase by 500cc or so. This increases the pressure so if you don't have a breather the excess will find its own way out......
Actually, reading your last post properly, there should only be one breather on the crankcase. Maybe someone has added an additional one?
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Hi Mike I think the breath…
Hi Mike
I think the breather you mentioned under the main bearing is not really required, it was only to drain any excess from the outer main bearing anyway,(and is often confused with a chaincase leak!) the main one is from the back of the crankcase on the drive side, it is hidden when the chain case is fitted.I blocked my smaller one about 4 years ago and no problems, I also fitted a pipe to the large one and it vents behind my rear numberplate.
Try and sort the ball valve problem out as my M50 doesnt wet sump with it fitted, (or leak any oil.).......Mike P is the man to speak to re-your problem, he is very helpfull, and has just rebuilt my engine.
A single with a roller big end does not require any where near the oil pressure as a twin with plain big ends, and as long as I see a return into the oil tank, I assume all is well..........
Regards John O
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If we think about it, whith the crankshaft installed in the crankcase, there is very little room. So, if the oil tank is emptying into the crankcase through the oil pump gears it will not take too much oil to fill it up. Once the crankcase gets half full the oil will find its way out to the breather on the left hand side.
Some people fit spring loaded check valves in the supply line to the oil pump but they run the risk of the valve failing and making the engine run dry.
Other than replacing the oil pump you can just run the engine every 3-4 days or baring that just drain the sump before you ride it.
Mike