DW_Crash,

Your symptoms sound the same as mine and at least one other person's I've read. You can read my posts about this starting here: http://www.rcuniverse.com/forum/fb.asp?m=3109179

In the end I sent my JJ1400 back to Joe and he sent me a replacement which I have over 50 flights on now but I had to have it balanced, free up the pre-load and replace the bearings and combustion chamber at around 25 flights (not hours)

Joe told me that the problem with the first engine was the rear bearing binding and dragging down the RPM causing it to shoot flames. Which I believe since my second (current) engine had pre-load issues as well.

As a test, push firmly against the shaft/nut on the turbine wheel as if trying to push the shaft out the front of the engine and then release. If the pre-load is free you should be able to feel or hear a very slight movement of the shaft against the pre-load spring and it will spring back when you let go.

Out of curiosity, try running the engine after pressing hard against the turbine end of the shaft (just by hand, maybe 20 - 30 lbs,) When it's cool and not running then run it and see if it accelerates ok for a while before going back to shooting flames.

Hope this is helpful, I've been there,
Mike