Hi Rob. Sorry didn’t. Engine is back together again. What I saw was that as I was lapping in the valves there was a darker area on the inlet valve seat where it passes by the exhaust seat which I couldn’t get rid of by lapping.
Ian W Sent from my iPhone > On 2/12/2020, at 9:56 AM, Rob Thompson <amessageto...@gmail.com> wrote: > > 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 >> >>