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Damp patch on top of crankcase 912uls

  • shay.king
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4 weeks 1 day ago #21590 by shay.king
Damp patch on top of crankcase 912uls was created by shay.king
Hi everyone,
Recently I noticed a damp patch on top of the crankcase on my 912uls [s/n 4428028 Spring 2002].

With SB-912-029 in mind I went looking for cracks but didn't find any.

After a 25 min ground run today I tried to see the source of the leak, initially there was nothing and then, after about 5 mins, I saw a droplet very slowly appear from the crankcase join on top centre. It was just enough to wet the top of my finger when I wiped it away. Then another droplet appeared appeared and I wiped it away again and so it went on.

During the ground run I could only get max RPM to 5050. Previously I had prop pitch adjusted to get 5300 RPM at full throttle stationary on the ground.

I checked prop pull through force with the engine cold and got a figure of 32 ft/lbs.
I checked it again immediately after shutdown and it was only slightly higher at 37 ft/lbs.
This was without removing any spark plugs.

The engine starts easily and runs smoothly.

Any opinion or advice on the above would be greatly appreciated.

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