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The oil in my WM20's chaincase is being turned into a milky fluid. It happened again yesterday, a 30 mile ride ruined new oil.
The chaincase looks in OK condition, has recently had a new felt pad behind the clutch, I've fitted a gasket at the joint with the engine, & I've fitted cork washers & silicone around the footpeg mounts.
The chaincase is sealed with a new cork gasket attached to the outer part with silicone, the inner seal is with thick chain grease.
I've tried a few types of oil. As an experiment I've blocked the inner side chaincase vent with grease.
There was almost no water on the roads on yesterday's ride (or others), just a few damp patches, & no covering of water spray around the bottom of the bike. The inners of the chaincase were thoroughly cleaned & dried recently.
Gearbox oil is OK.
Can someone help with any ideas?
The problem here simply overheating of the oil.The hot oil burns off the enzymes in the oil and these turn to steam and on cooling condensates down to water again mixing with the oil to form a suds type liquid.I would check the engine timing to ensure it’s not running too hot also remove the chain case cover and make sure the sprocket teeth are not blued.If they are then check the sprocket alignment as this also causes overheating.This was a common problem in the 1960s.
Thanks for the thoughts George. I checked the sprocket alignment & the clutch sprocket is about 1/8 inch outboard of the engine one.
This clutch has recently been fitted to a different gearbox & I stupidly didn't check the alignment when I put it together.
But I don't understand. This was a NOS clutch only recently fitted to the previous box & within pretty fine manufacturing tolerances these parts should all fit properly?
I'll check the engine cush drive assembly as well.
Is it milky or frothy ?
Lots of oils will froth up then condense back down as they cool
Do you have a cork or felt ring behind the clutch sliding plate ?
The cork will not hold much in the way of water but the felt will
Trevor, the oil's a milky yellowish consistency with no frothing. I made some on the bench by stirring together oil & water.
I didn't know there were cork rings available for behind the clutch, or did you make your own? Do you reckon cork would be a better sealant?
Have seen them as felt & neoprene cork
Think I have a cork one in at the moment
Was just a thought as clean dry felt can hold a lot of water
Thanks Trevor. I'll try to find something cork or similar. The felt ring in there now did have water in it. For now it's all going back together.
Well that will be the source of the water which is getting into the oil.
It does not take much to make the oil milky
Get a nice big bottle of the cheapest oil you can find then go for a nice long ride & change the 90ml of oil when you get home .
Repeat as often as necessary till the oil comes out clean, horrid thing to have to do on a nice sunny weekend .
Better still would be a new felt oiled with light machine oil before installed to prevent it adsorbing water
Apparently fabric treatments like ScotchGuard or even a water repellant like WD40 does a good job of keeping the water out of the felt.
Thanks for these ideas Trevor. It isn't all together yet, I can get some WD40 up there behind the clutch. Might even take the clutch off (again)to get a better shot. Wifey currently ransacking the laundry cupboard for Scotchguardy stuff.
It's meant to rain for a while here (about bloody time even if it does cut down the riding) so I've got the opportunity to do it all.