Ihave two OS FX 46. Both are broke in. Ihave adjusted idle transition and works good. Have run and adjusted both engines on ground and thought I had them right. Have been doing this since 1995 and thought I was pretty good with 2 cycle engines. But the other night I had both on these engines on my two planes die in the air. Not sure if I was to lean or rich. I held them up in the air like we rc'er do and they both ran great. Sounded good when I was flying. Then at about mid throttle they died. Is that lean or rich problem. It was real hot and muggy. Any ideas? I have not been flying much in the last 4 years and I'm starting to pickup again. So it's been awhile since the engines have run. How does a bad glow plug act?. Thanks

Until now I usually don't have engine problems.

ja, I'm having the same problem. I've been really good with OS 2-strokes, but converted to electric last year, or the year before? Anyway, took out my 120AX the other day and it quit on me a couple of times in flight. Amazing what a little time off can do for your ear/feel of an engine.

I'm sure you remember how to check the high end on the ground. My method for checking the idle mix is to run up engine on ground, drop to idle, and carefully watch the RPM. Should stay constant for a good 20 seconds, then start to drop. If RPM increases at all, especially in that 20 seconds, it's too lean.

How is the transition (idle to full power) on the ground? Hesitant, smooth, rough? If all seems good, may be the glow plug (can also be leak in fuel lines!).

My experience with bad glow plugs is that the engine just seems to quit for no reason - quits at any random attitude, not just climbs. Plugs are cheap and easy first solution.

Good luck,
Joe

It may not be a mixture issue....how old is your fuel lines? If you're dying with the same level of fuel in your tank you can suspect your lines......or it could be a glow plug....but just in case why not richen your high end about an 1/8 of a turn to see what happens

Also check your mid-range, Most people forget that important step. Check your glow tank, sump and fuel line to the carb. To narrow down your problem, I'd start with the mid-range- If it does it again then you've narrowed the problem down to glow tank, sump and or fuel line.

I rarely have glow plug issues and have used the same old plug for years in some of my engines. But it doesn't hurt to put a new one in anyway just to be on the safe side.


Pete

Try pulling the high speed needle out and flushing the system, then clean the needle good before putting it back. Sometimes I flush with a full tank through the muffler ( pressure ) line all the way through the carb.. If you use this method be sure you clear the system so you don't have a fuel lock. ( pull the plug and turn it through or spin it with the starter ) just watch your eyes when you spin it through. ENJOY !!! RED

I had the exact same thing happen today with my OS 46 and went dead stick. (landed it great thankfully)


I ran it on the ground and 3 times it died on me after the dead stick landing, it would die after full throttle and dropping down to idle. I took out the OS 6 plug that came with the engine (same one since it was new) and replaced it with a brand new OS8 and bam, problem solved. Ran great, got that nice "pop pop pop" sound and classic OS reliability.


Good luck!

Engines quitting after proper tuning? First thing is to try some fresh fuel and/or a new glow plug. Old fuel picks up water and makes it difficult to keep the fire lit. Old plugs can also have trouble with reliably lighting the fire.

I would suspect a bad clunk line in an engine that runs fine through half a tank and then suddenly quits. Either a hole in the line or slipped off the tube. If it's a hassle to get to the tank to check it, you can test the theory by seeing if the engine will run with only a little fuel in the tank.

You also didn't say what kind of planes you were flying. If the engines are in a cowl they may be overheating and shutting down, even if they are tuned right.

Good Point! Very true. It's funny but including myself I normally wouldn't think of that. But it once happened to me with my Hanger 9 Fokker DVII when I had a Evolution .61NX in it. You will notice that the engine is real hot, you can feel the heat radiating from the front of the engine. Also if you turn the prop by hand without the igniter attached, it will turn over tight. Plus if you were to feel the crankshaft it will be very hot.

I wound up making the air escape holes bigger under the cowl, and switching my engine over to O.S.

Also I switched my glow plug from a #8 to a #5 to solve my problem and it worked. O.S. seems to be able to take the heat better than Evolution, they have more power, way more dependable, and can take more abuse before any real damage occurs.

I have the new O.S.46AX and the engine is fantastic! Minnflyer did a write up on this engine and he's right on the money with his evaluation. Most all my engines are O.S. (4 out of 6)except for one and that is a Saito FS150GK new still in the box, and a new Super Tigre .51 that has a Perry Carb and Mac muffler.

Pete

Yes, on the heat issue I see scale modelers sometimes having to go to great lengths to keep things working here in Texas. The exit hole needs to be at least twice as big as the intake, and in some installations modelers need to build baffles to direct the air straight to the head. Adding some extra natural castor to our fuel can also help, as can running a little rich with the resultant power loss.

The OP didn't mention the plane he has but I think you hit pretty much all the bases. When I tune someones engine for them this time of year and it's flying along at mid throttle and just quits it often just needs to be richened up a bit. When a plane has been stored for a while and it keeps cutting out mid flight it is usually a bad line. This time of year I see a lot of engines that tend to over heat mid flight when they are tuned correctly on the ground. It is a wonder what just changing a glow plug can do too. When I pull down an old plane and start running it up I do as you mentioned and only fill the tank about 1/4 or so just to make sure my lines are OK.

Thanks guys for all the suggestions. Both my planes are profiles. So I don't think heating like inside a cowl is the problem. I know how to set the idle screw and high speed needle. Guess I don't know how to set the midrange. Had not even heard of setting it on a 2 cylce. I do know how to set it on a 4 cycle. Thanks

If everything else fails to fix the problem, you might try cutting the remote needle valve off of the backplate and mounting it separately.

The FX engines with the needle valve cast into the backplate were notorious for allowing the engine heat to transfer directly to the needle valve, which altered the mixture setting. The 91FX was one of the worst cases, which OS retrofitted with a different style needle valve that used a plastic housing to stop the heat transfer. I've seen at least two of the 46FX engines have the same problem. In both cases, cutting the needle valve off of the backplate and eliminating the heat transfer cured the problem.