New GX40 Gasoline engine
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TOPIC: New GX40 Gasoline engine

Re: New GX40 Gasoline engine 4 years, 6 months ago #209

  • victor
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I would try a different prop size, for example 12x4. Each prop size requires different carburetor tuning.

Re: New GX40 Gasoline engine 4 years, 6 months ago #210

  • hllywdb
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The GX40 works great with an 11X6. I would look at fuel system issues. Are you using the inline filter? Do you have the same issues when running on a test stand? Any fuel line leaks will cause this same issue.

Re: New GX40 Gasoline engine 4 years, 6 months ago #211

  • j.j.rutter
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No fuel line leaks, the inline filter has 2 mesh filters. Tank position shoud be fine, I'm reluctant to keep bench running it as I bought the engine to fly with not to just watch the prop turn round (fascinating though this is with a gas fueled glow engine)but even on the grund, while mounted on the model, it won't always pick up on opening the throttle. I tried an OS P4 plug but this was worse than the original so I might try a P3, the hottest that seems to be available as there's always a drop of rpm on disconnecting the plug lead. As it's nowhere near the rpm others are getting on an 11x6 on the ground or in the air (Eagle tree data recorder) I might try a 10x6 but I doubt this will fix the cutting issue.

Re: New GX40 Gasoline engine 4 years, 6 months ago #212

  • sirzepp
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I thought the p3 was the required plug? There has to be a simple fix...

Re: New GX40 Gasoline engine 4 years, 6 months ago #213

  • j.j.rutter
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Thanks for answering my queries, I've now got a "workaround" setting that works.

To get the model flying a tank out I now let the engine warm up thoroughly and set it to no more than 9,000rpm (fast four stroke) or about 1,500 rpm down on peak with the 11x6 APC while on the ground, glow lead disconnected. In the air the model will continue blubber around in a four stroke on mid throttle but after a few seconds on full throttle will gradually break into a 2 stroke as it warms to its task. Throttling back will put it back into a 4 stroke as it cools again. I also set a bit of throttle delay on my Tx to stop the throttle "snapping" open, which seems to help. I think I'm too used to flying electrics, which don't give a damn about how fast you snap the throttle open. This setting will let me fly a tank out and while it isn't entirely satisfactory (it'd be nice to get full power instantly on full throttle and not have to wait a while) it's better than it was and says a lot for the potential of the engine when it flies a 4 1/2lb model in highly aerobatic fashion even when not giving its all. Maybe part of the problem is a difference in UK spec petrol (gasoline) and US spec? There's now a lot of methanol in UK fuel.

Re: New GX40 Gasoline engine 4 years, 6 months ago #214

  • jfcgnv
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I hate to write this e mail. This engine is giving me fits. I'll admit I am not experienced with gas but this engine has me buffaloed!!

I spent all afternoon and over a quart of gas and I am nowhere near having a good running engine. I'll swear that my fuel system is not the problem. All new lines and tank and not a leak anywhere.

I can only get 10,500 at best and then only for a short period of time. The engine has yet to give me a smooth steady run, even rich with RPM down to 9000 range. I played with the idle and main needle to I am blue in the face. I will say that both needles are very sensitive and when you move one it grossly affects the other.

I was able to get a smooth idle and then the top end was very unsteady between a rich four cycle and a rough top end. When I got the top end to halfway steady (never was smooth) the engine would not idle.

The best I got was a idle of around 3500 and a top end of 9800 with an APC 11/6. Even here both idle and top end were not smooth.

When the engine is running with wide open throttle and richened just off peak 300 to 500 rpm it still ran rough and seemed to jump in an out of four stroke. I could see the exhaust change from steady to puffs of blue smoke then steady out again before repeating the same.

I even changed to a new P-3 plug with no improved results.

If this was a glow engine I would swear it was an air leak however I am positive that is not the case. I guess my next move is to try it with a little less oil or mixing about an ounce or two of glow fuel to the Mix.

Like I said this engine is driving me nuts.

John Castronover
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