My little ASP .12 engine seems to have inexplicably lost compression (not totally, but I'd say about half of what it was). Now it won't start for even a second at all. I've checked everything, from the compression shims to the glow plug. I cannot think what it could be. It seems to have literally happened between tanks for no reason at all.
I'm stumped here, is there anyone who could shed some light on this?
Many thanks,

When you say you checked the glow plug, did you check it for tightness or did you check the plug itself. I had a friend at the field lose compression on a Mecoa in the manner. Come to find out the ceramic insulator inside the plug came out and the compression was going out the glow plug between the body and the electrode. Just a thought.

Rob:

Is your little ASP a plain bearing engine? If it is it may also be pre-ABC, and have an iron piston in a steel sleeve.

It is possible you have been running it with a castor blend, or straight castor oil. Going to a 100% synthetic can cause a dramatic loss of compression with an iron piston engine, and if yours has a plain bearing crank, the synthetic wont lubricate it properly, leading to rapid wear.

On the other hand, if it's a late engine with a ball bearing supported crankshaft and an ABC cylinder, check the glow plug as suggested by cde and the head mounting. If OK yu've probably sucked some trash in and ruined the cylinder/piston fit. Using a castor blend might bring it back.

Also, if the engine is new enough you could avail yourself of warranty service to have it repaired.

Bill.

When I said I checked the glow plug I did also check the actual seal on the plug, I also tried different plugs (all Enya No.3's) and no change throughout. I've been using 20% castor, 10% nitro the whole time, so the oil is the right stuff.
BTW, I think it's a late engine (def. got an ABC). I'm wondering if the loud popping/banging noises from the exhaust which I have been hearing (or had heard ) have anything to do with this. As for the warranty, I want to avoid sending it back as much as possible since I have to pay the postage costs (mail ordered you see). I'll try it again tomorrow morning, I've left the plug out overnight on the window ledge so the engine can air nicely. If it still won't give anything, back it goes.

Update: I checked inside the cylinder and there are bubbles coming up on the side of the piston on thye downward stroke - not good. The engine is off to the place it came from.