503 Head Gasket leak


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Active Member
May 2, 2012
Calhoun, GA
I have a M-Squared Breese 2 with 503 DCDI 300ish hours. I have been battling a stubborn oil leak for a while now. Well I should say trying to ignore an oil leak for a while. Its a pusher and the rear cylinder head gasket leaks just enough for the oil to pass the gasket and slobber all over the tail feathers. I first pulled a compression check with normal results. After that i removed the head flipped over the gasket with no improvement. The previous owner had replaced the gasket three times. So i started ignoring it.
I recently had a friend with a 503 fresh overhaul and now he has the same problem engine runs great no temp issues but just enough leakage to make a mess. Is this a common problem with a common fix i have already recommended he contact his engine overhaul guy for answers. Just wandering if any of you had any advice.


Well-Known Member
Aug 14, 2009
I wonder are you using genuine Rotax gasket rings....alloy over steel...there are some cheap copy's about made from 100% alloy that are not supposed to be very good,

I also had a similar prob with mine some yers ago using Rotax gaskets....I was advised by my local Rotax guru here in the UK to make sure that the groves machined into the heads are deep enough and clean....if he heads have been surfaced a few times the depth of the grove is reduced to the extent that they don't bit into the alloy on the sealing rings,

I just went around the groves with a scribe very carefully and problem was sorted,

Also worth checking the head surface is flat and true.

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