As anyone would know that has visited most R/C sites over the years, I am a Thunder Tiger engine backer...they are ALL that I own in as far as modern engines (I've got a few McCoy Redheads). I've probably helped them sell a LOT of engines with my sharing the positive experiences I have had with their engines.

With that said...

To break in these engines don't baby them, run them hard right out of the box. Use a fuel with at least 20% lube, preferably ALL castor. Nitro should be 10% or less. Fuel for after break-in should be 10-15% nitro, 20% lube (1/2 castor, 1/2 synthetic).

For the GP .42 I would start with an APC 10x4 and an OS #8 plug. Get it on a test bench and fire it up. Get it to running a clean two-cycle run QUICKLY! Tweak the needle leaner unitl it starts to slow down then open it up 3-4 clicks. Run it through a full 8 ounce tank this way...at full throttle. Let it cool and do another 8 ounce tank with the same setting...at full throttle. Let it cool and check the air-bleed screw on the carb before the next run so that it closes off half of the bleed-hole opening, this is a good starting point. Check the idle stop by putting a builder's pin into the throttle rotor opening and adjusting the stop so that the rotor is set to be open the amount of space the pin makes at idle position, this is also a good starting point. Then do another eight ounce tank, this time vary the RPM some to see if it will idle. If the engine needs more full throttle run time it will die when you try to idle it down (still too tight), otherwise it will idle down fairly low. This engine's idle will continue to get better (lower) the more it is run. My GP .42's idle and transition are excellent for an air-bleed carb engine...I had to run the 'H' out of it to get it to idle down...it was real tight! You will have to piddle with the air-bleed screw setting and idle stop setting for a while to get it 'right' until about a gallon of fuel has been through the engine, then you will never have to touch either as it will run flawlessly.

Bottom-line, these engines typically come from the factory with a TIGHT TDC pinch that takes time to run-in. Do not even consider running this engine rich during the first hour of run time or you will lessen its usable life.

Should you have any further questions about TT engines contact ACE Hobbies (the US distributor) http://www.acehobby.com/acehobby/pro...nes/index.html I'd bet they would be able to email you a file containing the manual.