912 carbon and lead deposits
in 912 / 914 Technical Questions
11 years ago
I have a Rotax 912 ULS which has been exhibiting the following symptoms:
- Black velvet fouling on plugs
- Run-on after shutdown
My mechanic and I took the heads off and found significant carbon deposits. We expected to find some lead because the aircraft had been flown for 120 hrs in Brazil where all fuel has ethanol, so they used 100LL for the entire time. But the carbon was somewhat surprising. The carbs are adjusted properly and not rich, so that's not the source of the problem.
We cleaned the cylinders, plugs, valves and heads and installed new valve guides and all new gaskets. The engine now runs much, much better.
My mechanic noted that I wait until 50 degrees of oil temperature before runup which he thinks takes too long. I don't have a water temperature sensor at the moment (I'll install one) but he thinks the engine might have been getting too hot. Still, neither of us are sure exactly the cause of the problem.
Any ideas why this occurred and how to avoid it in the future?
- Black velvet fouling on plugs
- Run-on after shutdown
My mechanic and I took the heads off and found significant carbon deposits. We expected to find some lead because the aircraft had been flown for 120 hrs in Brazil where all fuel has ethanol, so they used 100LL for the entire time. But the carbon was somewhat surprising. The carbs are adjusted properly and not rich, so that's not the source of the problem.
We cleaned the cylinders, plugs, valves and heads and installed new valve guides and all new gaskets. The engine now runs much, much better.
My mechanic noted that I wait until 50 degrees of oil temperature before runup which he thinks takes too long. I don't have a water temperature sensor at the moment (I'll install one) but he thinks the engine might have been getting too hot. Still, neither of us are sure exactly the cause of the problem.
Any ideas why this occurred and how to avoid it in the future?
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