Hi All,
I thought an interesting situation I have had with these little engines. I "look after" ie the maintenance engineer for 3 limbach powered aircraft . 2 Grob 109's and our Dimona. One Grob has an L2400 engine originally in a Stemme S10. . The G109 with the L2000 lost compression after about 100 hrs (new heads from Nigel Baker) A leak down rest clearly indicated leaking inlet valves. The fix was to regrind the valves )not just lapped) and all OK. At the time I did think that the reason for the valve seat distortion was overheating as the L2000 in the Grob does run hot (as compared with the Dimona. Hoever I am currently working on the Dimona engine. It has done 500 trouble free hrs (apart from a failed Magneto condenser) It has had a frustrating oil leak so I have replaced the rear oil seal and was planning to lap in the valves. Here is the interesting bit .. There were clear signs that the inlet valve seats were slightly distorted in exactly the same area as the Grob engine. (but at 500 hrs, not 100) However our redesigned baffles etc of the Dimona installation does mean the engine is running very cool (CHT's around 110 to 140C and oil around 65C) Apart from what I am talking about, I am impressed with the overall condition of the engine. I had the valves reground in an engineering shop as just lapping the valves didn't totally seal the inlet valves So my conclusion is that there could be an issue that the heat sinking around the exhaust / inlet area is not as good as it could be. This is not serious though but if an L2000 has low compression that could be an area to look at. Best regards Ian Williams ZK-GCB New Zealand
