The ground runs showed that, now the left magneto was working nicely, the right magneto was probably also in need of some TLC. My engineers looked at it and established the points were badly pitted and needed replacement. With this done and the magneto re-timed the engine ran much better but #4 cylinder was still showing little compression when hand turning the propeller even with the engine warm, so I pulled the cylinder and had it looked at.
The bore, piston and rings all looked good. The exhaust valve was checked, usually the cause of valve leakage, but it was like new so all that was left was the inlet port. Once the inlet valve was removed, it was evident that both the valve and valve seat were covered with carbon. It looks like the cylinder has been run previously with inadequate valve clearance on the inlet valve. The valve was gently lapped and both it and the seat cleaned up nicely with no evidence of wear or damage. The cylinder was refitted and the head bolts torqued using my engineers borrowed socket extension. This has a curved shape and very thin ring to fit round the cylinders and allow the torque wrench to be applied - 25-ft pounds for the 3/8" bolts on the O-235 engine. All the valve clearances were checked and adjusted where required - a tight 5 thou clearance with the engine cold.
Then the engine was re-run and on checking afterwards the compression on cylinder #4 was much improved. This week, weather permitting, I hope to do a further engine run and then do a proper compression check with the differential tester.
I received the transponder back from Funkewerk this week. It had a display fault and although it was unused it was out of warranty - how many homebuilders suffer from things going out of warranty before they are ever used? Such are the timescales of homebuilding!
However, the service from Funkewerk was excellent, I received the transponder back within two weeks of sending it to Germany with a new release certificate and nothing to pay.
If the weather doesn't improve then the next job will be to upholster the seats - something that I can do inside in the warm.
