# SDR AU990440

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: May 7, 1999
- Submitted: March 26, 2000
- Operation: General aviation
- Make and model: Waco YMF
- Registry model: [Waco YMF](https://openairdocs.org/model/waco-ymf) (OpenAirDocs)
- Engine: Jacobp R755B2
- System (JASC): [8530 · Reciprocating Engine Cylinder Section](https://openairdocs.org/jasc/8530)
- Part: Exhaust Valve
- Part number: 12921
- Condition: Damaged
- Location: Engine
- Stage of operation: IN
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/AU990440

## Discrepancy

(AUS) EXHAUST VALVES ON ALL CYLINDERS WERE BADLY DEFORMED ON THE VALVE STEM TIPS.   INVESTIGATION FOUND ABNORMAL WEAR ON THE TIPS OF THE INLET VALVES.

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