Just bought a 10 oz tank, cut and installed the tubing and klunk according to instruction. After fitting, I found that when I position the tank vertically with the rubber stopper at the bottom, the klunk doesn't want to drop to the bottom !! Is the tubing too stiff or the klunk too light ??? Has anyone faced similar problems and how did you solve it ? I surely would'nt want to see my engine fuel starved on a steep dive...............

But it does! Sometimes the run of fuel tubing is so short that it doesn't have room to flex. Try either a different brand or try stretching that one out a little, sort of like a rubber band to loosten it up. Let me know how you make out_bob

If I'm reading you correctly, you're saying that when you hold the tank upright (with the stopper at the bottom) that the clunk doesn't go down toward the stopper. If this is indeed the case, you have nothing to worry about. It's not supposed to! If you are in a steep dive, negative "G's" will keep the fuel toward the back of the tank where the fuel is.

Not only do my tank clunks NOT go toward the stoppers, but I usually install a piece of semi-hard plastic tubing (supplied with some tanks) between the stopper and the clunk which is connected TO the stopper and clunk by two short pieces of fuel line. This is intended to PREVENT the clunk from being slung forward (toward the stopper) in the event of an abrupt stop (as in: a nose-over on landing.

This is exactly what happened to me several years ago. I was flying a demonstration at an EAA event, and due to the nature of the runway (which was not trimmed for such small wheels) on my first landing, my wheels got caught in the rough turf and the plane nosed over. On the next two flights, my engine quit shortly after take off. A post-flight inspection reveled that on the nose over, the clunk had whipped itself forward toward the stopper and got stuck there.

So DON'T worry about it!

I was referring more to some of those clunks that don't reach the bottom of the tank real well when level because of stiff tubing. You certainly don't want it so flexible that it will kink.

I had exactly the same problem, I was starting to get worried coz my engine quit just the other day after a shallow dive into a low fly-by.
My other problem is that the rubber stoper does not tighten fully and I was wondering wheather this would affect the presure significantly enough to stop the fuel after a de-acceleration?

Good flying
Ledz

If your rubber stopper doesn't tighten fully, I would replace it. Now don't get me wrong, I'm not one of those guys who thinks "everything has to be perfect". Quite the contrary. But I HAVE had fuel leaks in the tank compartment, and it can RUIN your airplane.

And those rubber stoppers can be tricky too. In fact, MY fuel leak was caused due to OVER tightening a rubber stopper. It was so tight that it caused the seam in the tank to split.

If I understand your statement, you have your tank plumbed correctly. Think of it this way, if your tubing flexed to the point to allow the clunk to come toward the stopper, then the kink in the tube would prevent the fuel from flowing anyway. The time spent at braking is not sufficient to cause the engine to stop unless you have extremely long down lines and fuel lines!

Ummm, not exactly. I was thinking along the lines of that the lack of presure would cause a loss of fuel. My reasoning for this is that it takes an elec. starter to get the engine primed and then you can flick it wif a stick, the fuel doesn't go thru so easily.

One of the things you can do is use larger fuel lines with a reducer at the engine/carb to reduce the flow resistance. I think your hard starting may be due more to the engine temp than lack of pressure.

flicking over an engine by hand alone wont prime it, putting your started on it forces it to suck, but at a slow rate. the trick is to open your carb fully, plug it with you thumb and flick it over 3-5 times, then close it again, attach your clip and flick it over.
i recently got a small 2oz tank and the tube was too still to leach the bottm when the tank was level , i just used some tubing with a thinner wall. i also use the soild joiner method to stop kinked klunk lines