Didn't get much feedback in the engine forum...so I thought I'd try here.

I have a new OS 46FX that was broken in with three good runs at a rich 2-cycle, alternating throttle settings on the second run, and peeked on the third. I peaked it at around 12000 with an 11x6 prop. I'm using 10% coolpower, 16% syth, 2% Castor mixed in.

On it's fourth or fifth flight, the Dubro quick fill valve leaked and caused the engine to go very lean in flight. Coughed and wheezed a few times and it sounded like it wanted to quit. I landed within 1-2 minutes when it didn't improve.

I put the quick fill valve on a third line to the tank with a clunk and plugged the output. I was only able to get 10,800 on the 11x6 prop and in two flights tonight, I had one dead stick at low throttle and the other time it quit on the ground after landing.

While cleaning up, I noticed that the exhaust residue was brown, not clear like I'm accustomed to seeing. Was that just the Castor oil or a bad sign?

Does it sound like that lean run messed this engine up?


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I had the same problem with the quick fuel valve. I haven't solved it yet but it shouldn't have hurt the engine to go lean for a short time unless they did something different to the FX engines. I get that color out of a few of my engines. It is over propped a bit. I don't run bigger than 10x6 on a .46. That may cause the less RPM, but not the color. Does it run ok now other than the color or is it still quitting at full throttle?

Nope, not quitting at full throttle, it's quitting at idle during aerobatics and landing. I think I can fix the quitting problem, it's the low RPM that concerns me.

I beleive OS recommends the 11x6 for the break in prop on this engine, I'll have to check. I know Tower lists it as the break in prop, and the RPMs were solid before the leak incident.

I wonder if the valve is still leaking and causing a pressure drop in the tank???

I guess I should also pull the cowl and re-check the throttle linkage for full travel.

I have to pull the cowel too and re plumb it. I think my valve might be the problem too. On mine, it is the 91 FX, it idles fine, just when I go to full throttle it runs fine for about 20 to 30 seconds and then dies like you shut off the fuel. I got it to run longer, but there are so many bubbles in the line now. Has to be sucking air somewhere. I have to check all the lines.

It could be a pressure problem, cut fuel line, fuel tank location, bad glow plug, or low end adjustment. Check all this out first. Usually it's one of these issues.

I had this problem several years ago when my FX 46 was new. Kept dead sticking on me after going to idle. After running rich 5 or 6 full tanks, I spent the time in my back yard adjusting the low end, and setting the high end right. Mines on a Lanier Twister swinging a 12.25*3.75 APC. 11*6 should work well on this engine.

My factory setting was a little rich on the low end. If memory serves me correctly I moved it lean about 1/2 turn total or something like that. Make sure when adjusting the low end you do it about 1/8 turn at a time until you transition properly. To date, it's my best most reliable 40 sized engine that I own.

Doug

I just cant be sure about the valve, so I'm pulling it off the third line and replacing it with a j-tec fill nozzle and plug. It's simple and then I can be sure I don't have a pressure leak on the third line.

Just when debugging the new airplane was plenty interesting, another variable has surfaced. When I took the cowl off, I noticed some pink dust on the engine. Upon inspecting the cowl, a bare spot where the red paint had been ground away is telling me that part of the shaft is rubbing against the cowl! That would rob 1000 RPM or so, no?

I just cant imagine how this is happening, however, as the cowl looks perfectly centered on the prop plate with 1/4" clearance all around, but the evidence is irrefutable. Maybe vibration? I just don't know how I can center it any better???

now that i know a bit more from your description here, it is always a good idea to run 20% for that extra little bit of protection, and as far as i know, you aren't supposed to run 2 strokes on 18%, i amn pretty sure they need at least 20%. if it was leaning out for 1-2 mins, and running on an unacceptably low oil precentage anyway, i think you have definatly trashed it. i don't mean to sound critical, but put in your cheapest plane, because i wouldn't rely on it, and it will probably not last the 20 years or so that these engines are known to last. if i were you, switch IMMEDIATLY to 20% if you want that engine to ever run nicely again. i am not sure what you guys do to your engines, but i've got an infinate idle on that engine. i have it in my trainer, so it doesn't matter much anyway, but it won't die unless it runs dry or i kill it

Well, as it turns out, the engine is fine. I replaced the stupid quick fill valve with the j-tec plug and the engine peeked the 11x6 prop @ 12,800 and I ran it at 12,000 to keep it rich.

Vertical was awesome, it idles smooth and it keeps chugging the gas at all attitudes down to the last ounce. It was a pressure problem.

Concerning the oil content, I really think the difference between 18% and 20% is negligible unless you are running the engine overly lean to begin with.

18% oil for 2-cycle is normal and just fine. It's also fine for most 4-strokes.

if the engine was running very lean for a while, i would take that extra precaution. it can't hurt, it only extends your engine life. ot he bonest, if you have heard that it makes engines load up at idle, it really doesn't.