I have an evolution 46nx that runs great on the ground but as soon as I get the plane in the air the engine quits usually within the first minute of flying.
Has anyone else had this problem and what did you do to correct?

I had the problem awhile back, what bI did to correct it-sold the engine and went out and bought a os46 ax no more problems

Bob A

I had a similiar problem on my Evolution. It would run great on the ground and then would blow glow plugs about every third flight.
I found that my HS needle was rotating due to engine vibration. I took some automotive fuel tube and slipped it over the HS needle and the problem when away. Check the LS adjustment and make sure it is not rotating.
If the engine will idle well on the ground and the transition is good then the LS adjustment is fine. If you set the HS needle correctly, then I would start looking for an air leak. Check all the fuel lines and the fuel tank first. Make sure the clunk is not stuck or has fallen off in the tank.

As far as needle walk...the high speed needle has a ratchet clip like most engines so that shouldn't be walking.
If it's the idle screw, I did have that on a GMS, and an old worn 4BK carb on a FSR 40. The fix was to remove the idle needle valve and wrap the threads with teflon tape. You can tell by adjusting the idle screw if t's loose or not.

Most modelers out there have bitter / sweet experiences with Chinese engines when they expect it to perform out of the box and to be consistent as an OS, which is ONE the most user friendly engines out there, certainly the most popular. You can remove the needle stops as recommended, get help from an experienced Evo owner to help you tune it, or punt. Thunder Tiger 46 is cheaper than OS and has a loyal following. http://www3.towerhobbies.com/cgi-bin...&I=LXKF97&P=ML, $95 before coupons.

Before you spent $100, what fuel are you using, what prop, what plug? Have you tried changing these items first?

Every month or so the Evo story comes up, some complain of a problem, people reply with buy an OS.
http://www.rcuniverse.com/forum/m_95...tm.htm#9590808

The Evo engines need a hot plug.

Also allow for the engine getting leaner in flight due to the unloading charateristic by stting the needle a little on the rich side on the ground.

OS A3 plus should be hot enough from what I've read. Horizon makes a $59.99 muffler for it now, from Jett engineering.
http://www.horizonhobby.com/Products...x?ProdID=EVOM1

Of course the same muffler fits many engines of the same size with the same spacing, Thunder Tiger, OS, Magnum, ASP, Megatech, Evo, etc.

The A3 is just what most Evolution engines need.

I know the 36, 40, 45, 46 and 52 need them, and have heard that the 61 does too. You get into a lot of problems with a colder plug.

I tore down an OS46AX for a friend to replace the bearings and the piston/sleeve because the engine had low compression. Price of OS bearings, piston, and sleeve are more than the complete engine. No thank you, I'll stick with Evolution.
OS bearings, piston, sleeve $135
Evolution bearings, piston, sleeve $45
Tunder Tiger bearings, piston, sleeve $54

I'm not impressed with the Evolution 46 at all. We tried for over an hour yesterday to set the high speed needle valve with no luck. Basically you could get the engine to run rich, then just sitting there at WOT it would go leaner and leaner till it died (or you closed the barrel just before it did. No air bubbles, hot plug, fuel line, tank and fuel good. Most likely an air leak somewhere that results in this behavior. I've been running glow engines for over 30 years and this is the first one where the high speed end couldn't be set. Maybe Horizon can correct the problem but I'd rather just get an OS 46AX.

Another student had a 60 size evolution in his plane that did run OK except that the low speed needle valve needed to be closed far lower than the installed stop allowed. Once that was defeated, the engine transistioned nicely and ran strong. Sealing an engine properly should be a no brainer but obviously the Chinese manufacturers don't really understand quality control. I've had other brands of Chinese made engine that almost always have air leaks when there is a problem.

I have a .36NX, a .46NX and a .61NX, all without any problems at all. But, I recall that Evolution had some problems with sealing the carb. Try putting a new "0" ring between the carb and spigot, and try putting fuel line on the needle valve. Make sure everything is tight and leak free.

When it is running erratically, try squirting some fuel along the carb base and/or along the needle where it screws into the needle valve. If the running smooths out, you have an air leak at that point. Good luck.

Sincerely, Richard

This is normal and explained in the manual. It is easy to reset the limiter for a new range. I think it takes a 2mm driver. The manual also explains how to remove the low speed limiter altogether. The limiter on the high speed needle knob should be a press fit pin. I took care of that with my Dremel.