To save you the trouble, hobbypeople.net carries XTM engines. I took a look there and they have a pretty good website. So good in fact, that I found the link to the manual for your engine:
XTM 24.7 PRO REAR EXHAUST BUGGY ENGINE WITH TWIN-NEEDLE SLIDE CARBURETOR
Just right click and save as... it's an adobe document. You need acrobat reader to open it.
I copied the pertinant needle setting instructions from the manual for you. Depending on how much you know about nitro, these are probably the break in settings, so they will be rich. But it gives you a starting point:
High Speed Needle Valve
The high speed needle valve is used to meter the air/fuel mixture at
full throttle. Using a flat blade screwdriver, turn the needle clockwise
to lean the mixture or turn the needle counter-clockwise to richen
the mixture. When you start the engine for the very first time, the
needle valve should be turned in completely, then backed out 3 turns.
When you start the engine after that, leave the needle valve in the
same position it was in when you shut down the engine.
Low Speed Needle Valve
The low speed needle valve meters the air/fuel mixture at idle and
during transition from idle to full throttle. Turn the low speed needle
clockwise to lean the mixture. Turn it counter-clockwise to richen
the mixture. The low speed needle valve is preset from the factory,
but minor adjustments may need to be made to suit your application:
fuel used, glow plug and environment all contribute to the setting.
To reset the low speed needle valve to the factory setting, follow
these simple steps:
1) Open the carburetor barrel completely.
2) While holding the barrel open with your finger, use a flat blade
screwdriver to turn the idle mixture needle clockwise until it stops.
From this point, turn the needle counter-clockwise 8 turns. This is
the factory setting.
IDLE Stop Screw (you may want to look at the download for this one, since it has a picture):
Please first familiarize yourself with the location of the idle stop screw using the photo of the carburetor on page # 1. The idle stop screw adjusts the closure of the throttle barrel. We recommend that the idle stop screw be adjusted so that the carburetor barrel stays open about 1mm. Turning the screw clockwise will cause the barrel to stay open more. Turning the screw counterclockwise will allow the barrel to close more.
