MK1 - After rebuild, oil pools in dished piston tops

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andy.hall
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MK1 - After rebuild, oil pools in dished piston tops

Postby andy.hall » Tue Jun 04, 2019 3:13 am

Hi all,
After a rebuild and gentlemanly low-rpm running tests of my MK1 I am a bit perturbed about oily plugs and pools of oil that form on the tops of the dished pistons. I have used Otto gaskets, with carefully added gasket goo around the pushrod tunnels, upper and lower surfaces. I have followed the initial torqueing down procedure for the head studs. My valve guide bores are unworn, and none of them loose. There's no significant exhaust smoke (yet). Cylinder bores and pistons were considered acceptable. There's a little oil coming out of the bottom engine breather tube. I see no problem with oil pump scavengeing, and being the plunger type I see wet-sumping as unlikely.
If the oil level in the crankcase sump is too high, for whatever reason, can it be that too much oil is being whipped up by the flywheels and sloshing up underneath the pistons, causing too much lubrication of the cylinder walls, leading to piston-top puddles ?

pkrichardson
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Re: MK1 - After rebuild, oil pools in dished piston tops

Postby pkrichardson » Tue Jun 04, 2019 7:36 am

Hi
My mk1 was just the same just got 300 mile on its back now and the smoke as just about stopped
Oil pressure as settled to about 35-40 PSI at 30 MPH in top gear from 60 PSI I think it was getting to much oil to the rocker gear with the high pressure but still leaks oil from around the head

Knud.Degnbol
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Re: MK1 - After rebuild, oil pools in dished piston tops

Postby Knud.Degnbol » Tue Jun 04, 2019 7:41 am

That must be loose valveguides.

john.whiting
Holder of a Golden Anorak
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Re: MK1 - After rebuild, oil pools in dished piston tops

Postby john.whiting » Tue Jun 04, 2019 9:45 am

Quite normal without valve stem seals......with flat or lumpy pistons,the oil will run back into the sump past the ring gaps...(slowly).....my Norton Atlas had yellow streams running down each exhaust valve and pooling in the closed valve when parked .....It helps a lot if the motor,and oil are very hot from a ton up run,as the thin hot oil quickly clears the surfaces and runs down,cold oil is thick and pools ...worst case is to start the motor ,run for a couple of minutes ,then stop.Bikes burn 1 gallon of oil every 2000 to 3000 miles when new ,a lot more when worn.


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