105 "sputtering"

[Chris Phillips]

I have been chasing a "sputtering" in my O.S. 105 for a while now, and I have exhausted my ideas, so I am reaching out.  The engine sounds like it is getting an air bubble in it.  It almost quits, but never does.  It always seems to catch again.  Here is what I have tried:

1.  SAB fuel magnet with new clunk line.  The back of the magnet is positioned right at the first bend in the tank
2.  replaced all fuel and pressure lines with new
3.  re-sealed the pipe to the header
4.  replaced front and rear bearings in the engine (in case they were leaking air)
5.  disabled governor

The sputtering happens at any fuel level, and in any attitude.  It does not seem to matter if it is flying backward or foward, inverted or upright, or pulling positive or negative G's.  Please give me something to try that I have not done yet!  This is too good of a heli to not trust it.

Thanks!

[alan]

Sputtering as in running rich or lean. An air bubble would cause a lean condition. Sputtering to me would be rich.
There is a know issue with some older main needle seats. The orifice was drilled too large resulting in a rich condition that made it difficult to tune. You might also pull apart the regulator. Clean it out with denatured alcohol. Check the needle is not sticking.
Cheers
Alan


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[cowboychris01]

By sputtering I mean in cuts off for half a second - enough that it makes me pucker a bit that I am going to have a forced auto.  So far, it catches back up every time.  It may run perfectly fine for two minutes, and then stumble 3 or four times in a 30 second span, and then run fine again for a while.


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[alan]

That really does sound more like it's going rich not lean.  So it would not be air bubbles.
Do check the regulator.  If it has debris or the needle sticks open this would be the explanation.

Cheers
Alan

[cowboychris01]

Thanks Alan - it will give it a look


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[Jon Yarger]

What FBL are you using? I had a similar issue that turned out to be a bad solder connection in the throttle output on my Neo. I could see the throttle servo jumping up and down while hovering. I could make the servo jump by tapping the Neo on the bench.

[Gabriel Sandoval]

i say it's a regulator problem. Take it apart and clean it up. Be sure you have the updated needle setup. update us with your findings.

[HelisRock!]

Looks like you tried a lot of things, and I'd have to agree it's probably fuel flow related, but you didn't mention the easiest change - the glow plug...

Is the fuel filtered between the jug and the tank, then between the tank and the carb?  I assume the inline fuel filter was cleaned/replaced at the same time as the fuel lines?

[Chris Phillips]

I cleaned the regulator, but still having the same issue.  I am not sure I have the updated needle set up mentioned above.  How would I know, or how/where do I purchase the new one?  Yes, I have tried a new glow plug, and that didn't help either.

[Rodney Kirstine]

You can tell if you have the right one by screwing the needle all the way out. If you can insert a 1.5 mm Allen wrench all the through the needle valve seat, you have the wrong one. If it stops without going in, you're okay.

[cowboychris01]

I will check it out.  Are we talking just the high end needle, or both?


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[Rodney Kirstine]

Just the high speed needle, yes.

[Chris Phillips]

A 1.5mm fits right in the orifice, so maybe this is the issue?  Is this the new assembly I need? 

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZTC7&P=Z

Or if I buy this one am I replacing the one I have with a duplicate?

Thanks for all your help guys.

[alan]

Call Hobbico. They will send you a replacement. They are aware of the issue.


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[Rodney Kirstine]

What Alan said, for sure. I've seen other people order one and still get the wrong one.