I hope you guys and gals can help, and mods if this is in the wrong place please move.
I Bought a trainer with GMS 47. I have tried everything to make it run, well I can get it to run but only for a couple of seconds before it dies. It is new and when I recevied it the mixture screws were wound right out.
I have set them to the inital settings as advised in the manual and played from there. I have changed the glow plug, inspected the o-rings around the carby. It seams to have good compression.
I have run out of ideas and would be grateful for any help you guys can give.

Regards,
Jason.

It sounds like the previous owner had the same experience and continued backing out the needles in the assumption that they were initially set overly lean.

If you have the model with the remote needle valve assembly, you should check the line from the needle to the carburetor for air bubbles. You should also consider taking the fuel tank and fuel lines out and inspecting the whole system. Many "engine problems" turn out to be tank or plumbing issues such as problems with the clunk line or a vent tube flush against the top of the fuel tank.

If the fuel setup looks OK and you're still stumped, find a flying buddy who is good with engines to help you go through the thing. Remove the carburetor and mount it again assuring pressure on the o-ring to prevent air leaks. Go around the cylinder head and back plate looking for loose bolts. Take a clean piece of fuel tubing and blow through the needle valve assembly to assure that nothing is blocking the flow of fuel into the carburetor and that the needles are passing air (and therefore fuel) when you blow into the tube.

The good news is that the GMS .47 is a terrific sport engine that is very powerful and transitions super fast when set up and tuned properly. If you work to get everything checked out and operating properly, you'll be rewarded with a powerful, reliable engine.

Good luck!

If the engine is indeed new i would probably take it off the plane and set it up on a pc of wood and do some bench running first, maybe spend the extra $5 and get a new tank for your bench running, this way if it runs fine on the bench then you know your problem lies in the tank installed on the plane. All new engines should be broken in first anyways, plus this will give you some experience with the engine before trying to fly a plane with it.

Yup as Bigedmustafa said, start by assuming that the whole fuel setup is bad or clogged.

That your engine runs for a few seconds tends to point to the carb, head, glow plug, etc. being OK, although your mixture may still not be correct.

An engine quitting after a few seconds can also be caused by insufficient tank pressurization....

Anyway, as he said, pull ALL of the tubing out along with the fuel tank.

Using a clean piece of tubing, hook one end to the High Speed needle inlet nipple and blow in the other end while moving the throttle control.

At full throttle you should be able to get a HISS out of the carb body as you blow.

Then check to see that the tubing and piping into and out of the fuel tank permit free flow in either direction.

Finally clean out the muffler pressure nipple. It may be clogged.

Bench testing makes all the difference in the world! And you can break in the engine in an optimum environment.

Thanks for all of your advice. I pulled it off the plane, built an engine stand for it, pulled the tank and lines out of the plane. Made it easy to set up and in no time at all she was running sweet. Have put most of a tank through it now with no problems.
Thank you all again.

Regards,
Jason.

I loved my GMS .32, I think you will be happy.

Glad to see you got it running, now a few more tanks thru on the bench and then it's time to fly.

Be patient, it has a good chrome bore and will take a little while to break in properly. But once it is broke in it will last, and last and last,,,,,,,,,,,,,,,,,,,, Just don't overlean it.

Well guys, I put everything back into the plane. I prime it up and when I am ready to start it the fuel runs back into the tank. Would I be correct in the assumption that the tank is too low in the plane. The plane is an Explorer 40 ARF and if I am correct then it either requires some surgery on the plane, or I would have to invert the engine and change the throttle linkage.
I did get it running in the plane with a mate holding it slightly nose down, once running it was fine due to the pressure from the exhaust in the tank (I guess).
Anyone else have this trainer and if so any ideas?

Regards,
Jason.

It is possible that the tank is a little low, you could have a small air leak, will it run back if the throttle is fully closed? As long as you get it running and it keeps going you'll be fine though. How much lead did you need to add to the nose to get that plane to balance?, i know my explorer .40 had a 32oz 21cc weedeater engine on it and the CG came out perfect.

Yeah, checked for air leaks, I have changed the position of the high speed needle which brings the fuel line lower in relation to the tank. It seems to be better. Thanks guys.

Regards,
Jason.

Sorry to bring an old post back from the dead - not really the done thing. That is what the search engine is for. But I felt I had to comment.
Tyrol - Nice trainer. I have an AT40 myself (which is exactly the same as your Explorer 40 but with a different name and colour scheme) with a GMS 47 in it, just like yours, except I made a few mods to mine - I changed it to a taildragger, put in 2 aileron servos and sanded the dihedral out of the root ribs so that the wing is flat with no dihedral.
It flies very well and the 47 has enough power to pull it vertical - after sorting out some CG issues.

Some GMS engines can be a bit temperamental. There is a very long thread on here about getitng GMS engines to run properly. Click [link=http://www.rcuniverse.com/forum/m_2290854/anchors_2290854/mpage_1/key_gms%252Ctuning%252Cproblems/anchor/tm.htm#2290854]here[/link] to check it out.

The GMS is a great engine. I have a .47 and a .61. Both are great performers, but they both required the carb drilling described in the link.
My GMS 47 runs circles around OS and TT engines of similar size.
I run mine on 1 gasket (they have 3 gaskets installed as they come from the factory), hot plug and 0% or 5% nitro fuel OS #3 plug for 0% and #8 for 5%. You don't need lots of nitro to make good power - no matter what people tell you. I'm talking about sport flying here, not pylon racing.

Do the carb drilling and enjoy your GMS engine.

Whereabouts do you fly?

Also, if you have the needle valve mounted remotely, move it to the carb. Unscrew the dome nut from the carb, take out the small plastic insert and screw in the needle valve assembly. The NV assembly and carb is designed to have the NV in either position. This seems to be very beneficial to making GMS engines run well. If this doesn't help , then do the drilling thing.

Hello all I have a gms 2000 .76 engine on a a6 texan. Does anybody know if you can put a different carb on gms like a os or magnum etc. I can't get it to run consistent at all all it seems to be sucking air from some were I might get it running decent then out of blue it stalls in mid flight. Had a bunch of dead stick landings which I don't prefer. You can close the throttle barrell all the way and it won't shut off. Anyone have any ideas before I file 13 it thanx scott