BIG BAD BOB

My Feedback: (119)

My 46 FXi idles and transitions to high speed on the ground but when I try to take off it will go down the runway about 10 ft and die. I'm running a nextstar 11-5 prop It tacks @ 13400 tops. I richened the mixture to show about 12900. Idles @ 2500. Any ideas would be appreciated

Bax

My Feedback: (11)

You'll need to check the fuel system. If the fuel pickup is too close to the rear of the tank, it can easily cause a flameout. When the model starts to accelerate, fuel rushes to the rear, this produces a temporary increase in fuel pressure, but enough to cause the engine to go too rich and quit. The fuel pickup should be no closer than about 1/4"-3/8" from the rear of the tank when the tank's held vertically.

Make sure that nothing is moving around. It's possible that something moves during the intial takeoff acceleration and is kinking or pinching the fuel lines.

pocatosaras

Hmmm, I have this same engine that I took off my Nexstar and installed it on a Super Chipmunk. I had to tinker with it slightly but generally it runs ok. Does it do this everytime? Have you replaced the glow plug (OS #8 works well)? As you take it off the stand and hold it vertical with WOT does it run ok? Have you crashed the Nexstar in the past which may have damaged the fuel tank connections? Have you checked your fuel/pressure lines to make sure there are no air leaks? What type of fuel are you using and have you changed the nitro-meth content (10% - 15 or 20)??

Any additional info might help us nail it down.

BIG BAD BOB

My Feedback: (119)

I'm running Wildcat fuel 15% nitro. Have checked all lines (replaced) clunk is about 1/4" from back of tank when held vertical. It seems when the prop unloads on takeoff it dies. It ran fine a week ago, but was running very rich, it would stumble when going from idle to full throttle but no problem after takeoff. It would run great at 1/3 to 3/4 throttle. I'm flying it in a hanger 9 Arrow

Bax

My Feedback: (11)

You have to check your settings and reset your engine. When the weather changes, you have to reset your carb. A carburetor cannot accomodate changes in the weather, and the needle settings can change a bit from day-to-day.

Richen the idle mixture a lot, get the engine running at full throttle and set the high-speed needle so that it's just rich of peak RPM, and then retard the throttle and work on the idle mixture. You should be able to find the correct settings. Unfortunately, we can't give you any particular settings because engine setting is unique to each installation and each day's flying. You cannot "set and forget"...over time, changes in weather will require you to change the needle.

BIG BAD BOB

My Feedback: (119)

Thanks Bax, I had the engine out at the field ths AM & went thru the set up as described. Still no luck. I opened the low speed mixture needle 3 turns from closed then started engine at about 2/3rds throttle, opened trottle all the way & adjusted Hi speed needle for top speed then richened mixture to 400 RPM below top, leaned idle mixture about 15 deg. at a time. Got a smooth idle at 2600 to 2700 RPM. Reset HI speed to top then richened to 400 RPM below top. Still would not transition from idle to hi on takeoff (running rich) Turned idle needle in a little at a time, checking each time, finally mixture screw was turned all the way closed with the throttle barrel just closed. Had to reset the idle but still would not transiton to Hi speed still showing lots of smoke & oil. Could it be a bad mixture screw or bad carb?
Bob

bkdavy

My Feedback: (1)

Replace the glow plug.

Brad

BIG BAD BOB

My Feedback: (119)

Hi BKDavy,
I replaced the plug twice today Tried an OS A3, Fox Idle bar plug, no differance, then put OS#8 back in. IT was installed new yesterday
Bob

BIG BAD BOB

My Feedback: (119)

Hi Bax,
I've tried about everthing I can think of ; Changed plugs, changed all fuel lines including clunk line, Changed to new jug of fuel, went through the complete set up as you suggested, made sure tank was not moving in plane(lines not kinking). Checked remote needle valve body and carb for obstructions, nothing found. I don't know what else to try. Maybe I should send it in for a check up as it is still under warrenty. I've had this engine since 9/23/2004 and this is the 1st time I've any problem with it. It has always started with 2 or 3 flips and ran great. Just don't know what to try next.
Bob

Bax

My Feedback: (11)

Before you send the engine in, you may want to run it on a test stand. If it will run 'all day' on the test stand, then there's nothing wrong with the engine, and you'll have to closely-inspect the engine/airframe/fuel system installation. The test stand will get everything in the open and you can make sure it's all positioned properly.

BIG BAD BOB

My Feedback: (119)

Thanks Bax, I'll give the test stand a try. I think I've tried just about everything else.
Bob

BIG BAD BOB

My Feedback: (119)

Hi Bax; We tried to run the engine on a test stand, but same results- no transition from idle to full throttle- cuts out at mid range. We tried swapping engine to another plane same thing. Put the swapped engine into my plane (a 46ax) and it ran great. If I send the engine in for repairs, should I leave the muffler on? Bob

Bax

My Feedback: (11)

Take the muffler off. You don't need to send it. It'll save you a bit on shipping.

BIG BAD BOB

My Feedback: (119)

Hi Bax, Sent engine in for check up on 11/18/2005. Thanks for trying to help. I'm curious to find out what the problem was
Bob

BIG BAD BOB

My Feedback: (119)

Hello Bax, Just recieved the O S 46FXi that I sent in 11/18, I never dreamed I could get such quick service!!! Don't know what the problem was with my old engine, but the technetion replaced it with a brand new one. Many thanks for the quick service and the new replacement. Bob