I have a TT GP 40 I bought NIB off ebay a month ago and have had one recurring problem with it. It runs just fine for awhile and then just quits. I have tried several different glow plugs and they all run fine until the engine decides to quit. The tank is new and has been checked for bad lines. The engine has been completely torn apart and checked for a defect in the casting or machine work. It is flawless. The carburator has been disassembled and checked. No air leaks or anything to block the fuel flow. The spray bar has been tried at several different depts and it runs anywhere you put it.

It doesn't matter if its leaned out or very rich. There are never any bubbles in the fuel line. I have tried it with the exaust pressure and with out. Same thing. It runs and then quits. I have tried 5 different glow plugs and they all work fine until it decides its through running. It will immediately restart too. The fuel is less than two months old and my other two engines run just fine on it so I doubt its a fuel problem.So I admit I am stumped. Can you guys think of something I have overlooked?

I have 3 of the TT .42GPs and they are normally trouble free.

First, check the pressure nipple in the muffler. If it is closed off, the engine will run for a while until the vacuum builds up in the tank, then it'll quit. If the nipple is clogged up, use a small drill or a wire to clean out the hole.

The TT .42GP has an air bleed carb. As a starting point, the air bleed screw should be half way across the hole on the front side of the carb.

Next, make sure you aren't running too lean. I'd start over by closing the needle, then opening is 2-3 turns. Crank up and leave the glow ignitor on the plug. Lean the engine until it breaks into a 2-cycle. Don't peak it out until you are sure it will stay running.

Ed you may have solved the problem. The nipple was semi clogged. I would have looked a long time before I checked that. I will try the motor tommorow because right now I am dieing from a cold. I took the muffler apart but couldn't find what was plugging the hole. I sure hope that fixes it. Like you I have owned 3 TT GP42s and they have all been very good motors. The little Tower 40s were also good dependible engines.

I love the simple air bleed carbs. Once you know how they work they are the most dependable carbs you can get. At least to a point.

Well I just tried it and that wasn't the problem. It still dies for no reason. That I can see.

The odd person has reported engine troubles like this, related to expansion as the engine heats resulting in air or compression leak. Engine runs fine, then as the heat soaks through the system the trouble brews. Sorry, can't be more specific as I have never had this myself, but it is a scenario consistent with your descriptions. Just a thought.

Hi!
Are you sure the engine gets fuel!??
If there is fuel to the carb the engine cannot refuse to run! Simple fact!
Screw out the high speed needle and blow trough both the fuel nipple on the carb and the fuel intake orifice.Finally check that fuel enters through the nipple by blowing through the pressure line when the tank is filled (so you see fuel entering the carb).

Then use fuel containing 5-10% nitro...more is just waste of money!
Use an OS 8 or Enya 3 glow plug (there are ofcourse many more glow plugs that work too, but those two are "the old stand by's").

Use a 240cc (8oz) tank! No more!!!!
Very important! Always place the tank according to the tank mounting rule, preferable with two clunks (Uni-flow set-up).
Use a 10x6, 11x5 ,11x6 or 12x4 prop depending on model, preferable a RAM or APC prop!

Finally, start the engine at idle and run the engine at full throttle...check the engine setting by holding the nose of the model straight up! Adjust the engine from there!

Okay I think the problem is solved. I went to a local HS and picked up an OS LC4 plug as recommended by another poster here. Did it fix it? Nope, still died. So I tried the only other thing I hadn't done. I tried a brand new, unopened can of fuel. Bingo. It ran an entire tank and never missed a beat. I let it idle for 2 minutes and got instant excelleration. I am glad thats over. That engine was about to become a target for my deer rifle.

Now what I don't get is why does my FP 25 and a TTPro 46 run perfectly on the fuel I have been using but not the TTGP 40? The fuel I have been using is Omega 10%/18% oil. The new can of fuel is Powermaster 10/18. The Omega was bought near the end of december and the powermaster 2-3 weeks later. The omega has never sat open or in the sun. So I don't know. Oh well such is life.

Anyway thanks for the replies and suggestions. Don't give up. Just keep trying something new. The answer is out there. Somewhere.

Good news! When in doubt, check the simple things, eh?

Yes simple is good. Working on the same fuel I have already been using is even gooder.

Both of those fuels are a little short on oil. They are fine for ball bearing engines as they need less oil. Plain bearing shafts need a little more. you were probably running a little hot. Continued use of low oil fuels leads to a prematurely worn out engine. How long should one of these engines last. The answer is literally years of continuous service in not an unreasonable expectation. That is, provided you give them what they need to survive and really all that is needed is keep it clean and keep it oiled.
Dennis

Ihave to agree Dennis, I prefer 20% lube in all my engines. SIG Champion is the preferred fuel at our field.