Low effort required to turn prop on 912

[Bluey]

I was turning the prop over by hand as I always do before the first flight of the day yesterday when I noticed that at on point in the cycle the torque required to turn the prop was quite low, lower than usual. The engine is a 912ul and its on a trike. The engine started normally and all the temps were fine and oil pressure was fine too. I flew and all seemed normal. The engine has 620 hrs and when compared to other 912's in the hangar, the torque required to turn those props was more, however all were different. I checked a brand new trike and while it had more resistance it wasn't that much different. Another trike with about 150hrs had significantly more resistance. My engine has synchronised carbies (checked a few hours ago) but always is a little rougher than a new trike. I've been told this is quite normal according to the experience by others on older engines. I've had the trike for more than 200hrs and the effort to turn the prop by hand has always been lighter than on other trikes. It's a 2009 model. In comparing to my old trike 2008 model, the torque required on that was much higher even when I sold it at 613hrs. In fact it was tighter than any other prop I'd hand turned.

 

Should I be concerned?

 

Bluey.

 

 

[DGL Fox]

If I were you, and I am not an expert by any means, but I would get someone who is qualified to check it out if you are concerned.

 

David

 

 

[planesmaker]

Have a simple leak down test done on it. Must be done with engine warmed up. A cold pull thru it is not uncommon to have 1 cylinder different to others. A leak down will tell you if you have a problem. Tom

 

 

[Bluey]

What happens if the leak down test shows a problem?

 

Bluey.

 

 

[planesmaker]

Have somebody qualified to do the leak down (a respected L2) they will know what to do next. If you don't have much experience with rotax engines, get someone else to look at it, that's the safest way. Tom

 

 

[Bluey]

Thanks.

 

I know a good level 2

 

 

[Tomo]

Well spotted, have that leak down done and you'll soon find out whether you have a soft cylinder. A leak down is good because it will help you know if it's piston rings or the valves that have the issue.

 

Good question and I commend you on wanting to check it out.