OIL!!!!!
Now this is something that confuses loads of people who are new to M ownership, they are a 2 stroke but not a fuel/oil mix. There is no need to mix oil with the fuel, why? Because Petter have a clever system of lubrication. This post covers the ring oiler M range only, not those with greased main bearings.
So how does it work? Well, the bearings have oil wells on each side, we will concentrate on the left side for now, this has a drip oiler, either a cast pot or a glass oiler and tube that goes into the oil well just behind the governor arm bracket, this is to replace oil used to lubricate the big end, how?
Like this….
The crankshaft has a ring on it that turns with the crankshaft, this lifts oil and deposits it on the shaft, this then works its way along the crankshaft, helped along by a scroll machined into the shafts and when it gets to the end it then goes via a hold drilled in the crankshaft to the big end journal, this is then used to lubricate the big end and then thrown around the crankcase to lube the little end and cylinder, extra oil slosh around in the sump and generally gets thrown everywhere.
The oil is kept inside the housing by a clever conical washer and a groove in the outer cover, there is no seals, no felt seal, no rubber lip seals or cork washers.
So basically, as long as you have around 16 to 20 drips a minute going in that should be enough to keep everything working spot on👌
Imagine showing the inside of the end cap
Showing quite clearly the oil return groove and cutout for the oil to return to the well
Conical washer
These are handed and should only be fitted one way
Oil ring, this is what lifts the oil from the well and deposits it on the crankshaft where it then goes through the bearing
Showing how everything should be when fitted, ring hangs down and the conical washer is between the ring and end cover
Ring in place, you can just about see it turning with the crankshaft
Groove in the crankshaft to carry oil to the big end which is then thrown around the crankcase to lubricate the other internal bits.
Hope this helps to understand how a Petter M works, its a clever system. Does not apply to those fitted with greased main bearings!
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Country: GB