Thanks for the support guys.

With the F1 looking like a snooze-fest, I headed out to the field, the weather station at the field said ~28 deg C.

As I was sharing the field for a change (Sunday afternoon) I was being polite and limiting the flights to about 15 minutes. The first two flights were OK, no misfiring but the engine felt very flat especially off the bottom end and I was having to throttle up to 3/4 throttle just to hold speed on 45 deg uplines.

I leaned the high speed two clicks for the third flight and pushing over the top of the old Half-clover it didn't feel right and the power starting dropping off pretty quick over the next couple of passes so I landed, took the belly pan off and richened it up three clicks. Took of again and flew for a few more minutes with the belly pan off but the power was just flat but at least it wasn't misfiring.

When I landed I flipped the plane over to check the valve clearance, and noticed when turning it over TDC that the "bounce" wasn't there. The tappets had clearance but there was very little compression. The piston, ring and liner were replaced a while back to try and fix the problem with no success and I replaced that ring only 4 litres of fuel ago in case I'd cooked it at some point so it should be bedding in fine by now? When cold there's a real kick turning it over so the lack of compression at running temperature was a surprise. The new head assembly should be sealing, so it's like the new ring has lost it's tension or maybe the cylinder is going out-of-round when hot?

Sorry about the long-winded post, but I ran it without the bellypan but I still haven't gone the glow plug route yet. I'd be disappointed if the pump had worn out as it's done very little work. I'm very reluctant to buy another YS but I don't want to convert this to electric as (a) It's already heavy and (b) I'm not set up for 10S flying so there's a significant investment I need to make for the resultant 8 minute flights.

Anyway, I can't lose anymore sleep over this as the MotoGP is on at 4am and I need my beauty sleep, good thing I've got Monday off work....