i'm running an evolution 46nt in a hangar 9 pulse using 5% non branded fuel and the original glow plug.

I ran good when new got a couple of flights out of it but then started to get problems. When you full throttle nothing happens and then after a few seconds it speeds up then tries to cut catch it and the same cycle happens again and we seem unable to tune it.

I noticed a split in the pipe to the carb so replaced this with a similar dia pipe and looked like it was sorted, stated first time would go to full throttle ok, but first flight out engine tried to cut on take off not 10 feet of the gound then had no full throttle but idles nice.
can anyone help as i'm tearing my hair out, could it be the fuel, we've had the tank out made sure the fuel is not foaming checked the other fuel lines and the plug looks ok.

G'day Mate,
The first thing I would do, is replace the plug, use an OS #8, glow plugs don't last forever, & try some fresh fuel, that way you start, from a known good starting point, tune from there.
Also don't run too lean, from your description, it sounds lean.
Run motor up to full throttle, on the ground, with new plug & fuel, & lift the plane so the nose points up, & listen, if it speeds up a bit it is OK, if it doesn't, it is too lean, open high speed needle, 3 clicks, & try again. It must speed up or it will surely go lean & stop as soon as the nose points up after take off.
If you try to get it screaming on the ground, it will be too lean in the air, as the motor unloads it needs more fuel, so don't run it lean.

I have 3 Evolution 46's and 1 .61 and I use nothing but 15%. 10% ok, but I think in addition to the suggestion above (richen a little) I would run no
less than 10%. I have never had a minutes trouble with any of my Evolution's.

I assume the engine comes with the installed restrictors on the adjustments. I would remove that from the high speed needle valve. The high speed needle valve is the one inthe fuel line from the tank. To richen up the engine you unscrew it, do that in very gentle steps, partial turns (or as we say clicks). The high speed needle valve has a knurled surface and a spring clip to keep it from moving when set. That is what makes the clicks. The high speed needle valve should be somewhere between 1 1/2 to 2 full turns out. Two turns being rich, 1 1/2 being lean.

Tune the engine by ear for max RPM, then move the high speed needle valve out a few clicks to richen it. Once you get this down right, the next step is to tune the low speed adjustment. It is found inside the throttle arm on the opposite side of the carb from the fuel line coming in. It is buried down in there, usually slotted so that a small screw driver is needed to adjust it. When adjusting this do it in small steps, no more that a 1/8 of a turn at a time.. An 1/8th of a turn inward leans the engine at idle, an 1/8 of a turn outward richens the idle.

With the high speed adjusted, slow the engine to idle, if it does not idle at all, then it is to lean. If it idles okay and the engine stubbles when acccelerating, it is to rich. Adjust with the engine stopped for safety's sake. Once an adjustment is made to the low speed, start engine and test again to see if it idles correctly and accelerates smoothly. If it does that, it is near perfect.

Cheers,

Chip

My Evolution .455 TPS and .46NT both did the same thing. I would work the throttle up and down until about mid throttle and let it run maybe a minute. Then, I would work the throttle until it was wide open. Sometimes, if not careful, the engine would die.

W8YE was flying at the club then, and he gave me an older Towers plug which is hotter than the OS 8. That cured the problem big time. I also had a lot more power as the engine was burning the fuel better. It was like getting another 1/4 throttle added to the engine. If you don't have a Towers plug you can try either the OS A3 or a Saito SS plug and see if that cures the problem.

Stevebow, I'm am currently working on a similar problem as you. I called horizon hobbies and they told me the factory needle settings

are 1 1/2 turns out. This is a good starting point. I have new 15% fuel and I am using OS 8 plugs and neither have helped yet.


Also make sure the carb is tight to the engine, mine was coming loose at one during flight. [sm=eek.gif]

I have 3 of these engines. The 1 is for sure you are using the wrong fuel. 10% or better as said above. Also you can remove the baffle in the muffler. It will increase the power allot! Some say it will cause you to lose back pressure to the fuel tank but, mine run fine. these are good little engines. Evolution claims they are broke in from the factory but all of mine needed to be broke in. I notice the more you run them the more reliable they become.

As mentioned above, I have also found that they seem to like a warmer plug. I have 3 Evo's and have either a Hangar 9 Super plug like the one it came with, or an O.S. type F or similar. I am thinking that perhaps all the extra fin area on these engines make them run cooler, and thus they need a warmer plug? Oh, and I too use either 10 or 15% nitro fuel...usually Powermaster...and they run great

proptop and I have the same experience. I use the Hangar 9 super plug and I have had excellent service with them. Rarely have to replace one.

Thanks for all the advice i will be trying to ge the thing working again this weekend