Wont run when pointed UP
 

Hello again ;)

I have the nexstar .46 trainer. and it has flown 2 flights, but now I cant keep it running when i pint the nose up in the air. If I have it full throttle and then turn the plane up it starts to bog down and will die out on me. Any ideas?

RE: Wont run when pointed UP
 

The high end is too lean.

Open the high end five clicks, then with the plane level run the engine up to full throttle.

Hold it there for 10 seconds or more then point the nose up.

The engine should speed up a bit and sound more powerful, but it should continue to run.

If it seems to slow down ONLY when pointed up, richen the high end needle a few more clicks.

You'll find that when everything is correct the engine will seem to run a bit faster with the nose up.

Once this is so ( assuming you have a full tank ) point the nose about 25 degrees down, and perform the same test.

The engine SHOULD slow a bit more, but should continue to run.

If all of this is working, test again with about 1/2 a tank of fuel...

Note however that on a nose down test with less than 1/2 tank of fuel, you may find that the engine will die as the clunk becomes uncovered.

This is normal, it also happens in flight, which is why sometimes people have unexpected deadsticks... not too much that can be done about this w/o resorting to bladders, etc.

RE: Wont run when pointed UP
 

I will try your advise first thing in the morning. I wonder if My carb may be clogged or somthing. I had it pretty rich for a while.

RE: Wont run when pointed UP
 

Maybe the feed line inside the tank fell off - so when you point it up, you're sucking air

RE: Wont run when pointed UP
 

Opps, Forgott to mention, I took the fuel tank out and replaced all of the fuel lines from the clunk out, just in case there was a pin hole.

RE: Wont run when pointed UP
 

Did you check to see if the clunk is free? You can check by shaking the tank and hearing it bounce in it. Did you smack the plane on the ground on a not-so-smooth landing? I snagged a tree on an abnormally low approach a couple of weeks back and realized that the clunk slid forward and got stuck forward, soing the same thing. Also, it was dying after a few seconds just at WOT (wide open throttle).
Good luck,
Curtis

RE: Wont run when pointed UP
 

Yes, clunk is completly free. I took the tank apart to make sure all was good. It has to be something with the carb... Is there specific ways to clean out a carb. We have small little black flies that can get in the carb while flying.

RE: Wont run when pointed UP
 

Before you do ANYTHING, try what I said in the prior post.

ALSO be sure that the nipple from the muffler is not clogged with debris ( HIGHLY LIKELY!!! ) or gunk from the engine. This WILL cause what you are seeing as well!


If you are unable to tune the engine, then take the carb off.

To clean it, remove the nipples and needle valve. You can usually leave the throttle barrel in place, but it wouldn't hurt to remove it as well.

Wash the carb & barrel in warm water to dislodge anything.

Before you do this, make sure that you have removed all loose parts, remember that a grommet, or spring may still be held in place by fuel or moisture.

Dry then blow compressed air through everything, particularly the nipples and the nipple seats, and the needle seat area.

Hook up a clean piece of fuel tubing and make sure you can blow air through all of the fittings and orifaces.

Once done, rinse everything in fuel, clean, put everything back together carefully and again rinse in fuel to be safe.

Adjust the needle to factory defaults and again check to airflow on the rebuilt carb.

Replace on the engine and retune.

Note that you'll have to start the tuning process all over again.

RE: Wont run when pointed UP
 

I'm curious, you say you have flown the plane twice? How much fuel (tanks) have you run through this engine? And if memory serves me correctly that plane came with a O.S. Max .46FXi ..... correct?

RE: Wont run when pointed UP
 

Good point... after only 2 flights it is unlikely that carb fouling is an issue at all.

Either the engine is mistuned, needs a bit of retuning, or he has a pressure / plumbing problem...

RE: Wont run when pointed UP
 

Yeah, I'm thinking the engine is still getting broke-in and all it should need is a little adjustment....

RE: Wont run when pointed UP
 

Have you tried pressurizing the tank. Take the tank out and plug all of the lines but one. Put it under water and blow into the open line and see if it bubbles. The tank must be sealed completely for muffler pressure to pressurize the fuel.
Good luck,
Curtis

RE: Wont run when pointed UP
 

The engine is a JBA .46 It was new.

Here is my story,

I put the plane together and everything. Had a club trainer take it up for me. It stalled going up and crashed...No big deal as it was in a corn field and had only tiny strut damage.

Second flight went off ok for a minute, then the pilot said it wouldnt respond to throttle. After he was able to stall it and bring it in, we found that I had not tightened the carb all the way and it came off the engine. Seemed like it was full bore, It must have still been able to get the fuel.

I tightened the carb down and it was flown a final time with no issues at all. I tried to fly it the next day and it ran in a flat position but wouldnt run well pointed up. As you increase the throttle, it would die unless brought back down. We tried tuning over and over but no sucess upright.

The fuel I was using was 15% Byrons Heli fuel straight Sythetic.

All fuel lines are brand new to make sure. clunk is free. I will do the tank pressure test as well as clean the carb thourouly. Ill get back to you guys on the results.

RE: Wont run when pointed UP
 

Dying as you run up the throttle indicates that the high end is not set correctly...

USUALLY it means the engine is too lean on the high end, OR that there is insufficient tank pressure to drive enough fuel into the carb.