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-   -   Trouble with Evolution .36. Air in fuel lines? (http://www.rcuniverse.com/forum/beginners-85/11619131-trouble-evolution-36-air-fuel-lines.html)

hiTmanhiT 07-02-2015 08:44 AM

Trouble with Evolution .36. Air in fuel lines?
3 Attachment(s)
I have a Evolution .36 mounted to an Extreme Flight Outlaw.
I've always had trouble getting it started and keeping it running more than a few seconds. Yesterday I fired it up, and got it running for a couple of seconds.

I noticed some air bubbles right after the HS needle in the fuel line when it was running. I also saw some air bubbles before the HS needle after it had stopped. Where could the air leak be?
Tank? Fuel filter? HS needle? Carburetor?

I'm also running it on a O.S #8. I've heard Evo-engines can be picky on plugs. Any suggestions on a better one for this engine?

Thank you so much. Here is some photos of the fuel lines right after it stopped.


JohnBuckner 07-02-2015 10:43 AM

OK you say it has never run for a few seconds which requires a question and that is: is that needle limiting device functional and is it preventing the needle from closing completely then allowing at least four full turns open.

I think if you get rid of that limiter (an abomination) completely screw the needle closed then back out 3 and a half full turns (360 degrees), you will find success and hopefully a nice maiden flight.

By the way I googled Forde, What a lovely town.


hiTmanhiT 07-02-2015 11:07 AM

1 Attachment(s)
Limiter is removed and I've tried all kinds of needle settings!
2 turns out, 3,5 turns out etc etc...
I've gotten 1 flight out of it once, but that's years ago. That's the only time I've gotten it to run properly.. But that was after alot of trying. But next time, same stuff.

Førde is quite beautiful! So is our little airfield! About 40 min from town though!

jester_s1 07-02-2015 06:58 PM

Air bubbles before the needle valve is a tank or fuel lines problem. Replumb the tank and be gentle when you reinstall the tank. Also replace the fuel line between the needle valve and the carb. Bubbles after the needle valve indicate bad o rings in the needle valve usually. As you've seen, no amount of tuning will make an engine reliable when it doesn't have a reliable fuel supply.

jaka 07-03-2015 06:44 AM

Air bubbles in the fuel line always mean a leak in the tank! So remove the tank and test it!

Scar 07-03-2015 09:50 AM

To be clear, air bubbles at the carburetor occur when the clunk line in the tank is cracked or loose, allowing air to enter instead of fuel.

And, if the clunk line is too long, the clunk might squirm around to the top of the tank, where air would enter, rather than fuel.

Air Leaks can also occur outside the tank, at the tank / line connection or at any line connection between the tank and carburetor.

Good luck,
Dave Olson

jetmech05 07-03-2015 11:00 AM

Bubbles after the high speed needle indicates a leak at the needle. Bubbles before the needle indicates a leak from the needle all the way to the clunk.
Sounds like you have more bubbles after the needle than before. Replace all the lines from the clunk to the carb and a new o ring in the high speed needle.

Gray Beard 07-03-2015 04:08 PM

I enlarged the photos and couldn't see any bubbles in the tank line at all but wanted to see what happened when you removed all that hardware John pointed out. That is one funky remote housing too. I'm not familiar enough with the Evo engines but I would be doing a reverse pressure test on that housing to see exactly where it's leaking.
I use one of those squeeze bulbs used for ear cleaning for pressure testing. I put a piece of brass line in the bulb then attach some fuel line to it, put some fuel in the bulb, attach it to the nipple on the remote and give it a squeeze. Wherever fuel or bubbles flow out is where the leak is. Could be the O-ring on the needle valve or those two screws in the housing look suspect to me too??

hiTmanhiT 07-07-2015 07:06 AM

Tested it for leaks. Was definetley leaking somewhere. But was not able to determine where excactly.
Was definetley not the tank, but I'm suspecting the fuel filter or needle. So I've changed all the fuellines and removed the screws on the HS-needle, and removed the gasket in between as it was fuel-soaked and rotten.

Hopefully this will bring more success!

jester_s1 07-08-2015 07:31 AM

In a severely demon possessed engine, I once took it off and put it in a sink of water so I could pressurize the engine by blowing through the fuel line. If you'll block the carb intake and the exhaust, you'll find any air leaks in the engine. In mine, I found that the engine was sucking air through front bearing very freely. A new bearing made a major improvement.

castlebravo 07-08-2015 09:09 AM

Is that a screw together fuel filter on the feed line from the tank to the NV....get rid of that...they are notorious for leaking. Try connecting a basic known good tank with nothing but a clunk, vent, and good fuel line to the Needle Valve......if it still does the same thing....you know your tank and plumbing are good and you need to start looking into what is at or after the NV. Also replace the tube going from the NV to the carb...they can develope small air leaks too.


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