Profile for John Rutter (j.j.rutter)

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  • Register Date: 31 Oct 2012
  • Last Visit Date: 17 Sep 2014
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emo
I agree it sounds very like a pinhole problem but it isn't. I've replaced the pick up line twice - just in case - but on neither occasion has it made any difference as there was no fault with the line. It's got to be a tnak fault of some sort as the engine runs so well for the first 2oz or so of fuel and shows no sign of "stress" prior to stopping as if out of fuel. I'm looking into supporting the tank in foam to see if it's a vibration/foaming problem, about all I can think of as everything else seems fine.
New GX40 Gasoline en ...
emo
Got a slightly odd problem with my Gx-40 in a plane. Since putting a fatter O ring under the carb the engine's now starting and running beautifully, expecially on a 10x7 prop, idles slowly, picks up cleanly, plenty of power - for about 8, 1/2 minutes, then it stops. Very strange as there's enough fuel for 15 minutes in the tank and if I drain it through the fuel line there ar no air bubbles or any other problems. This is fine in a way as 8 minutes is enough for a lot of fun, I just changed my timer settings and land it after 8 minutes but why should it stop? The tank is new, flat rectangle shaped, 4oz capacity. The clunk reaches the bottom properly but doesn't meet the rear wall (which sometimes causes suction blockages), it doesn't leak, all the pipes inside and out are fine. The change in fuel head is ony about an inch from full to empty, much less than it seems happy to suck fuel through when the models nose is pointed to the vertical so surely a change of 1/2" (8 minutes of flying) can't be the problem can it? Yet it consistently cuts, even on tick over (which I left deliberately a little on the rich side) after no more than 9 minutes. Refilling the tank it'll start and run on exactly the same settings in exactly the same manner but still stop after about 8, 1/2 minutes. Good consistency but slightly frustrating. Anyone got any thoughts on this?
New GX40 Gasoline en ...
emo
I had similar problems but think I might have found the answer. The O ring between the carb and crankcase on my engine was very thin. I replaced it with a fatter one, pushing the carb tight against the crankcase while tightening the pinch bolt and got a much more consistent engine run. Of course now the carb. settings are all to pot as they'd been adjusted while seemingly having an air leak around the bottom of the carb. I'm not 100% sure I've cured the problems but I've certainly improved things. My engine also seems happier on a 10" prop, just as well as I've run out of 11x6's with the number of "flame out" into long grass landings I've suffered.
New GX40 Gasoline en ...
emo
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.
New GX40 Gasoline en ...
emo
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.
New GX40 Gasoline en ...
emo
While I'm impressed with my GX-40 I can't get it to run reliably in the air, it "flames out" after a minute or so, usually as I open the throttle from about the mid throttle position (where it seems to run sweetest). It idles reliably and picks up cleanly but even though I set it into the air "slobbering rich" it's still likely to make a lean seeming cut after a minute or so. The tank is only 4oz (good for 15 minutes of flight plus landing reserve), laid in a flat rectangle position and is at the correct height and as near to the engine as possible. Prop is 11x6 APC, which, even after well over 2 hours running is only turned at 10,500 rpm peak, I take off with far less than this. Any ideas on why it's so unreliable. I've tried opening the idle needle to see if this helps the lean seeming mid range but this just seems to spoil idle (3,500 minimum before it stops)and pick up.
New GX40 Gasoline en ...
emo
I found out the hard way that medicinal castor isn't good for engines many years ago by seizing a new ST G20/15 I was running in but the GX 40 needs castor oil in the premix but, after a lot of internet searching, I've found that unfortunately 100% pure castor oil just doesn't seem to be available in the UK, the nearest being Maxima 927 which seems to be largely castor with some additives. Shell castor M seems similarly to be castor based but not pure castor. Castrol R (which I remember from the '70's) doesn't seem to be made any more. Other than Klotz (which doesn't seem to be available in the UK) is there any other make of oil out there that might be available in the UK to suit this engine?
GX 40 oil
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