912UL exhaust valve
in 912 / 914 Technical Questions
13 years ago
Has anyone else, besides me, seen an exhaust valve start leaking at 190 hours since new? I have a 2009 912UL that has 190 hours on it. It is installed in my Northwing Scout X-C trike. I use it for instruction so it gets used regularly. Plus as a LSRM and Rotax heavy maintenance tech I take very good care of this engine. A couple weeks ago I did an annual on my trike. When I did the compression check the #1 cylinder was down to 82/87 with pronounced air leaking from the exhaust. All the other cylinders were 86/87. I know it was within acceptable limits but at 190 hours there is no way it should be down. I pulled the #1 cylinder and looked at the exhaust valve. What I found was pitting on the valve face. I use only 91 octane autofuel, no 100LL. I change the oil every 50 hours and use Aeroshell Sport 4 Plus.
There is no way there should be any pitting on the #1 exhaust valve. I ended up lapping the valve face to at least get the compression up to around 85/87. But I can still feel the compression isn't the same when I tune the prop over for an oil level check. Three cylinders feel good the last is mushy. At thsi point I am about ready to buy a new exhaust valve. But this is suppose to be a 2000 hr engine. Didn't say anything about having to replace valves during that 2000 run.
As an aside I just did an annual on an Air Creation Tanarg that is 4 years old with a 912UL that has only 92 hours and was not flown very regularly. The Tanarg cylinders checked out 86/87 across the board.
There is no way there should be any pitting on the #1 exhaust valve. I ended up lapping the valve face to at least get the compression up to around 85/87. But I can still feel the compression isn't the same when I tune the prop over for an oil level check. Three cylinders feel good the last is mushy. At thsi point I am about ready to buy a new exhaust valve. But this is suppose to be a 2000 hr engine. Didn't say anything about having to replace valves during that 2000 run.
As an aside I just did an annual on an Air Creation Tanarg that is 4 years old with a 912UL that has only 92 hours and was not flown very regularly. The Tanarg cylinders checked out 86/87 across the board.
