Do you have photos of the distortion/damage to the valves and seats? regards Rob
Rob Thompson 0429 493 828 On Tue, Dec 1, 2020 at 6:55 PM Ian Williams <i...@agcon.co.nz> wrote: > 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 > > >
