When I used to work as an auto mechanic my boss used to say that to make an engine run you only need three things - spark, air, and gas and that everything else was just tuning. Since this is a glow engine we can change spark to "a reason to fire" and gas becomes glow fuel. The air takes care of itself.

Before you look at the engine, check out your fuel. Is it new, or did it come with the old engine? If so, it's suspect. Methanol (the main part of glow fuel) will keep virtually forever if it's sealed up well but it is hygroscopic, meaning it'll absorb water from the atmosphere if not sealed up properly. There's no real way to tell if it's absorbed water (if there's a fair bit it might get cloudy) and it's almost impossible to remove the water (no, you can't freeze it out - the water molecules are bonded to the alcohol molecules) so if your fuel's old and suspect throw it out and buy some new fuel. You also need to have the right amount of oil in the fuel - I'm not familiar with Thunder Tiger's but typically 15% oil should be fine. You'll probably also want some Nitro (nitromethane) in it... typically 5-15% is heaps for two stroke engines.

The first thing to do on the engine is to get a new glow plug. FYI a glow plug works because of a reaction between three things; heat (initially from the battery, later residual heat from running), pressure, and a catalytic reaction between the methanol in the fuel and the platinum coating the plug's coil. The platinum will wear thin sooner or later which is why plugs stop working, even though it'll still glow with the battery connected.

The second thing to work on is the carburettor. Check to see that the carb is firmly mounted against the crankcase and that the O ring sealing it there isn't cracked/missing/etc. A loose carb or damaged O ring will allow air to get in which will make the fuel mixture very lean (too much air, not enough fuel). Check that the barrel rotates freely and doesn't feel "gummed up" with old fuel/oil. You need to check that there's no fuel blockage too - do this by connecting a length of fuel line to the inlet nipple, opening the barrel wide, and blowing into the line. You should be able to hear air hissing through the carb - if not try open the high speed needle a few turns and try again. If there's still nothing, pull the carb apart and find out why. If old fuel has evaporated in the carb it can leave the oil (often castor oil) in there to turn into gum which will stop the fuel getting where it needs to be - you can wash this off by soaking it in new fuel and carefully wiping with a coitton bud/cloth etc.

The next thing to check is the mixture settings. Your carb will have two settings - the high speed needle which will be fairly obvious, and a low speed needle which will probably be a screw hidden in the throttle shaft. Rather than typing out the whole procedure for setting the mixture here, just [link=http://www.lymanslack.com/Articles&Archives/st.htm]click on this link[/link] to go to a good article about it. It addresses Super Tigre engines but the principle is the same.

Finally, go over the engine and make sure all screws etc that are supposed to be tight are tight. Once you're sure you have fuel, air, and an ignition source all the right places and proportions, fuel up the tank, open the throttle wide, cover the air intake of the carb with your finger and turn the prop through a few (2-3) full turns to "prime" the carb (this sucks fuel out of the tank). Then close the throttle, connect the glow starter, and start the engine.

Oh, and I'd really suggest investing in an electric starter - it makes life much simpler. Good luck, and let us know how it turns out.