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HomeAircraftHelicopterHelicopter Main Discussion › clunk lines
10-13-2005 07:54 AM  13 years agoPost 1


Richfield, Minnesota

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ive found a new heli field close to my home, and while its not an actual model field its much much bigger than the park i normally fly at and its pretty much deserted. Anyways so im flying and my engine quits, its the clunk line again, so i decide this time to replace it with some different stuff, before i had gone with the expensive little short line that comes with buying a whole new clunk, because it was the closest to the stock stuff i could find. Close meaning that it was thin wall tube, but anyways i ask the hobby shop kid for some new clunk line and he points me to the fuel line and there is no thin wall stuff to be found so anyways i get the 'small' line and while the line is abou tthe same size as the stuff i used before the wall is thicker making the actual inside smaller. I suppose this is going to throw my engine tuning way off but what im wondering is who actually uses this stuff, it seems to me that it MIGHT be a problem as this line will allow for less fuel flow than the thin walled stuff.

Also my tanks are leaking now and i dont want to replace them because its too expensive i think i can get more use out of them, but the header tank is leaking at the seal where the nipple goes in and the main tank is leaking from one of the dimples that hold it in the frames, i tried repair of the main tank w/ some zpoxy but it still leaks, anyone here got a sure fire way to seal up these leaks cuz i really dont want to spend 40$ on new tanks.

Raptor 30 v2 / OS .32 / JR 8103 / GY-401+9253 | Raptor 50 V2 / OS .50 Hyper

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10-13-2005 10:37 AM  13 years agoPost 2


Honolulu, Hawaii

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For the clunk line I use Hayes Clunk Line. As for the hole in your main tank, you can use a soldering iron and melt the hole closed. I usually get some strips of plastic from a fuel bottle or a broken fuel tank and use that for solder. It takes practice to get good at soldering plastic. I practice on some scrap pieces of plastic before I do the real tank. The header tank I always buy a good CNC nipple tank like the Quick UK ones. It will probably be the last header tank you will buy.

Take Care,
Cheers, Patrick

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10-13-2005 01:49 PM  13 years agoPost 3


Sandy, Utah

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A new tank for a rappy 50 is under 10 bux from that extreme place in Hawaii, the nipples on the tank get chaffed easily from inserting the tank into the frames after replacing the clunk line because of the sharp edges it has to pass while sliding in, the solution is the Hayes fuel line for the clunk, and sanding the sharp edges from the frame edges. The black Hayes line will easily last 6 months or longer, making replacement costs alot cheaper. Get a new tank, and a header tank. put hayes fuel line in them right from the start, sand the edges on the frames, be done with it all for a very long time.
On the frames, dont be shy about rounding the edges of the area the tank slides. All edges in the lightening hole areas and the rear edges. bevel good all edges leading into the small indents the nipples on the tank locate in.. Easy 10 min job.


10-13-2005 02:03 PM  13 years agoPost 4


Jacksonville FL

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I'm curious Foo.

Would it be cheaper to replace the tanks or the helicopter if you flame out at an inopportune time because you didn't replace the tanks?

AMA 77227

10-13-2005 09:30 PM  13 years agoPost 5

rrKey Veteran

Junction City, KS

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If you think that a $10 tank is expensive then I believe that you selected the wrong hobby to pursue....

I second barracudahockey here, what is more expensive, a tank or repairs on a heli after a bad auto. Assumning that you can auto.

Regular fuel line is good enough for a clunk line. how long do you keep your heli pointing straight down? (Assuming that the clunk points to the rear of the heli) And if you do, do you have a header tank?


Keep your feet on the ground, but your eyes on the sky.

10-13-2005 10:14 PM  13 years agoPost 6


UK. Herts

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I usually replace my clunks every 3 months due to them splitting. I've just got some new clunk line which has a wider bore, so it slips over the nipples far more easily. Will be interesting to know how long it lasts.
Never had a problem with tank failure; i think its just a case of mounting them well.

10-13-2005 11:03 PM  13 years agoPost 7

rrKey Veteran

Clarkston, MI

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cheap crap header tank that came with his Raptor kit.
I have two season on the stock TT header tank in my Raptor 50. Is there supposed to be a problem with it?

10-13-2005 11:34 PM  13 years agoPost 8


UK. Herts

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The problem is with the clunk lines on two counts. The bore of the line is too small which results in it splitting. Secondly, the muffler pressure feed results in corrosive exhaust gasses eating the clunk line. Clunk tubing and normal fuel tubing is probably made of the same stuff; I use fuel tubing in my fuel bottle and have been using the same piece for years, so that piece of tubing has been sitting in clean fuel constantly and there aint nothing wrong with it.
On the subject, I have just upgraded my 90 Cspec with a Cline, so the tank pressure is derived from the engines crank case pressure and NOT the muffler. This means that there will be no nasty exhaust gasses in the fuel tanks. It will be interesting to see how long the clunk lines last.

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