This post started in 2008 if you seach tt 07 diesel on the site you can pull it up, it suffers from low power as glow and Davis pulled it from production ( the head) since not that great as diesel, having a little time decided just to try it again it will still fly a small electric conversion, got it to fire off a prime but would not stay running
turns out the O ring missing from needle hence sucking "wind" not fuel you cannot get just the o ring comes with the needle, so just gambled about $7 dollars for the needle assembly, from tower really too bad TT has not addressed the issue neat little engine well made , angle needle valve martin

Which model do you have, early or later model? How much pinch do have at TDC?

The later ones are better than the earlier ones, and they are close to a Norvel .061 RC on a 6x3 prop. With a turbo plug head it will slightly out-power the Norvel .061 but can not match the .074. So there is nothing really wrong with these engines (at least on the later model).

The o-ring on the needle is not diesel compatible, you'll need to get a viton ring or something else than the stock material.

You could also try a Norvel .061 with an RJL head instead. Less weight, no o-ring on the needle, and Norvel seem to run well on diesel too.

Mr cox think finding that small an o ring a challenge, good compression but no pinch at TDC, it was run back in 2008 as far as new or old issue a guess with the fins at the bottom of the cylinder looks like the newer one?? martin

You could possibly cut a new o-ring from a piece of neoprene tubing, I think you do need a seal there.
The newer one has the three topmost fins of the crankcase with a larger diameter, and the alignment pin for the cylinder is also solid. I've test run mine on diesel, with a glow plug and all shims removed, it felt quite alright but the o-ring couldn't take the fuel.

Here is an image of the latest model:

Mr Cox looks just like it I count 4 fins is is red anodized however martin

It is the fins in the crank case that is the best identification, the newer model have the top three of case with a larger diameter.
The head can be anodized or not, but the different outside of the crank case also means that it has a better matching on the ports on the inside. The solid alignment pin for the cylinder is also a telling improvement, the early ones had a hollow pin that would release crank pressure (visible with a magnifying glass or the bubbling of oil during running.

Mr Cox just checked it is the older version, however have the newer version on the shelf, will put the diesel head on that one thx martin