Hello Everyone:

I hope this doesn't turn into a "Ford vs Chevy" discussion, however, on there are things which go by the name of "bubbleless clunks" which are supposed to cut down on air bubbles getting into the fuel line.

Do they work?

The reason why I'm asking this is because I have something like this fitted to my plane, last Sunday for no obvious reason the engine went lean. When I got home I notice that the bubbleless clunk was partly blocked. If it cuts down on air bubbles getting into the fuel line, I will gladly clean it every few months, however, I'm now wondering if it's doing any real good.

Bye, Ian

From my experience they work as advertised.

However you can still suck air into the system anywhere between the clunk and the spray bar through a tiny hole.

Hello W8ye;

I've swapped the old clunk and replaced it with a new one. I've cleaned the old one. I know that there are lots of places air can get into the fuel system or it can become blocked. I'm changing things one at a time to nail down the problem.

Thanks for your time.

Bye, Ian

The one I used drew fuel around the outside of the whole clunk instead of the end so it's not good to the last drop so to speak but they work

Does anyone have a picture of one?

skiman,
i saw that very one at the shop this evening, looked like a fishtank oxygenator, it had an os label on it and cost 16.99. i saw it and thought that the tank would have 3/8" fuel left at the bottom and be sucking topside air already...
they have a selection of the cylinder type but they were solid with no o-ring.

The OS one is $14.99
http://www3.towerhobbies.com/cgi-bin...&I=LXXF25&P=ML

Here's another from Dubro for $1.99
http://www3.towerhobbies.com/cgi-bin...?&I=LXD741&P=7

Here's a different type from OS that is $7.29
http://www3.towerhobbies.com/cgi-bin...?&I=LXXF26&P=7

Bit of difference in price wouldn't you say????

I have the OS one
unless you have a real tight tank intall and can't get much foam in I don't think it's needed myself

The ordinary felt clunk will empty the tank to the last drop AND have ample flow AND prevent bubbles as long as fuel keeps the felt wet.

Sintered clunks:
The $1.99 type works well in RCcombat planes. It is about the smallest available, and also is used in air cylinder silencers.
the plastic sintered type like in Ryobi engines and the $7.29 type , gave me too high fuel flow resistance values after a while, so I will not use these again

Im using the dubro sintered clunks in all my tanks, both for filter purposes and minimal foam issues. They work nicely but i always wondered what if one of those small metal balls got loose?? i dont even want to think!

I always wanted to give the felt ones a try but usually found them not enough weight. could someone post a good solid felt clunk option link? thanks!

I've used these on my gas models and I've watched the tank as the fuel gets low. They suck every last bit of gasoline from the tank without a single bubble in the fuel line.

http://www.horizonhobby.com/Products...D=ZEN550085400

Hard to believe?

They might not have enough capacity for a Moki or big engine on glow fuel?

As long as there is liquid to soak up, the capillary action keeps the clunk felt filled with fluid, effectively blocking all air passage. The fluid filled clunk is heavy enough to work well. With the tank full, it need not tough the bottom. With the tank near empty it will.