chewy

What are you guys using for the clunk line on your gas engine? I have Tygon on mine and it's too stiff to allow the clunk to fall forward on down lines. Thanks, Matt.

MercerAUST

I think there is another current thread on this topic (perhaps under Saito engines). There is an alternative 'black' tubing you can use (available at most LHS in packaged short lengths. This is less stiff. You can also look at a standard felt Walbro clunk (available from any shop selling brushcuttersand chainsaws etc) which is much heavier and very effective in filtering and sucking up all fuel at any angle (only a portion of the clunk needs to be in contact with a splash of petrol and it will suck it up).

krayzc-RCU

My Feedback: (31)

also the clunk does not need to go forward on gas engine planes.......

aussiesteve

The Black tubing that is becoming very popular is Viton Tubing. One source of it in the USA is McMaster Carr. Most decent automotive suppliers wil be able to get hold of it also.

[link]http://www.mcmaster.com/#viton-fluoroelastomer-tubing/=g2wxoo[/link]

I use genuine Tygon in all my installs. There are a couple of differnt Wall thicknesses available. I use the thinner walled one with the Walbro clunks it is more than adequate. I leave a little fuel in the tank when finished and rarely have a need to replace a line.

One of the lower cost places to get hold of genuine Tygon is from the Briggs & Stratton stores. Here is another place.

this is the thin wall if you want real flexible.
[link]http://www.amazon.com/Oregon-Fuel-Line-Tygon-25ft/dp/B000SL28DS[/link]

this one is the thicker wall that also works fine with a heavier clunk if you are concerned about the price per foot.

[link]http://www.amazon.com/Briggs-Stratton-695541-Inner-Diameter-50-feet/dp/B0038U3JFW[/link]


There are a number of "lower priced" alternatives that may or may not be as good.

As mentioned, there is no need for the line to move forward on a downline on a gasser due to the fuel pumps on gasser carbs.. It takes a very long downline to cause an engine to starve of fuel.

hobby_man

My Feedback: (8)

stick a couple inches of copper tube inside the fuel pick up line to keep the clunk from the motor side of the tank.
I use a heavy clunk and the Tygon gets softer by the way once exposed to gasoline.

Barbs/zip ties/clips on all the tank fittings, inside and out

3136

Are you getting dead stick's?

chewy

Yea. On extended down lines.

speedracerntrixie

My Feedback: (29)

Most likely it's too low of an idle and/or too rich on the bottom end. I have never had that issue even with a 3W 170. I have never set up my tanks where the line went to the forward of the tank.

rhd-RCU

My Feedback: (36)

On the downline , the fuel should be forced to the back of the tank.

MTK

What?? Idle would have the plane in free-fall and at 1 G.........You're kidding right?

krayzc-RCU

My Feedback: (31)

http://www.youtube.com/watch?v=WtbSqEtLQX4



here is a video to show what the fuel tank is going thru[8D][8D][8D][8D][8D][8D][8D][8D][8D][8D][8D]

av8tor1977

My Feedback: (6)

Cool video. I saw one similar a long time ago, but it was very poor quality. What camera did you use for this video?

AV8TOR

krayzc-RCU

My Feedback: (31)

no idea on the camera as it not my filming this was posted a while back on the soda bottles for fuel tanks on FG forum[8D]

3136

You have probably already done this, but I would check that inside the tank it isn't sucking air, look for cracked lines check they are cable tied or wired well.
The heavy felt clunks from mower shop are great too.
I fit my fuel tanks sideways in the plane sometimes, I never did it for that reason but in an extended dive the clunk would be just sliding to the side of the tank.
As far as clunk line goes, the mower shop sold me some opaque grey tube that is meant for a ryobi line trimmer, 1 year later and it looks brand new, very flexible.
I would be looking for an air leak first.

When you are on your down line how long is "extended" also what throttle settings is it happening at?

chewy

Maybe 4-5 seconds. Usually at an idle so as not to overspeed the plane or engine. So what y'all are saying is the clunk sticking out of the fuel for that long wouldn't possibly cause a deadstick on flare? The tank is less than a year old. Replaced it because the old tank had some age on it. I don't remember using anything special on the old tank but this engine is extremely reliable and never deadsticked before. I assumed the Tygon I used to replumb it was too thick. It's an old Brison 2.0 with a Dubro tank. Was always rock solid reliable.

oldtyme

Check this link: http://www.rcuniverse.com/forum/m_10930918/tm.htm

It's a thread I started here in Gas Engines and this subject is well covered there.

Cheers,
Andy

skillet92

WOW!! great vid that shows what happens!! Unless you have lllooooooonnnnnnnngggggggg down lines you will be ok with most gassers!!

3136

Chewy 4-5 seconds will not be a problem at all.
If you are at idle when it is happening I would put it down to tuning or just too low revs.
Try and keep the revs up just slightly and see what happens.
Have you changed fuel, oil, props or mix ratio?
Maybe just a retune could cure it.
I would probably check the plumbing again though.

chewy

Haven't changed anything but the fuel lines. Ill tune the bottom end and see if it helps. Thanks