ORIGINAL: setxws6
So are you guys saying that my problem is in the idle bar on this set up? How well will the engine idle without an idle bar? I've never used them without one.
Definatly do NOT use an idle bar plug. Not needed. No engine made after 1990 that I know of requires one for normal operation. Idle bar plugs were designed to keep the plug from going out during idle and transion in the days when RC carbs were kinda crappy. Modern, well designed carbs with two mixture needles, and even most air bleeds, can establish the proper mixture to permit good throttle response and idle... while using a standard glow plug.
Plugs - Rossi 3,4 K&B1-L, OSA3 or A5, McCoy 56/59 are suitable for the TT .46 engine. The K&B HP plugs are also a good choice. OS#8 maybe. Tower plug (as noted), Merlin, Fireball, H9 'hot" plugs and sport plugs are good too. Fox, others should work, just try them out.
As for blowing plugs...
Engines blow plugs NOT because of the compression or plug selection (not this type of TT sport engine you brother racing guys.....)
They blow plugs because of a lean run.
Two things to remember.
1) Always set the engine about 500-600 rpm down from peak rpm on the ground. When the plane gets in the air and jumps on the muffler, its going to further increase in rpm, and its going to need more fuel. If you do not provide that fuel in the first place, its going to go lean and blow the plug.
2) If set like note above, and the engine still blows the plug, you have a fuel system problem. Very likely you are experiencing fuel foaming. After about 1/3 tank, the engine will start sucking the foamed-up fuel, and will go lean erraticly, and will blow the plug. The fuel tank must be isolated from the airframe - foam padding - it may not touch anywhere. Also, ensure the prop is balanced. At the higher rpm you are seeing on this setup, the energy transmitted to the airframe (and thus fuel tank) is substantially more - so a foaming problem may appear where one never may have existed before.
Also, do not fly the tank dry or below 1/3 tank if you can avoid it. You are guaranteed to pick up air through the clunk - one good air bubble will get you lean condition and a temperature spike - poof.... plug is gone.