bylandandair

Flying a modeltech magic fun fly plane with an OS 52 four stroke and when on a down line it very often dies no matter if it has a full tank half or low fuel. What could be causing this and what could be some solutions?
Thanks [8D]

davidmor

Could the clunk tube be too stiff to allow the clunk to drop all the way down? With a small tank, and short piece of tubing the clunk will stay towards the back of the tank no matter what angle the plane is at. If the fuel is anything less than completely full, it will start drawing air and kill the engine.

bylandandair

Thats what I'd think, but then I read in another thread that some people seem to think that you do not want the klunk to drop to the front as it will usually get stuck and they use some brass tubing to help stiffen it.
What is most commonly followed? Allowing the klunk to fold over or not?

bikz

make sure it does
add wait to it if you need like tying a piece of nut with wire to it.
i have the same plane and have done that to make the clunk drop.

davidmor

I do all of mine to allow the clunk to fall forward. If I am afraid that it will stick there, I put more weight on it. I take a nut big enough for the tubing to slide through, and slide it on before the clunk. Then I tie it off so it stays at the bottom of the tube. That gives it more weight and will let it drop back down instead of getting stuck. I have also heard of others who add a glob of silver solder to the clunk to make it heavier. I haven't done that just because I have always done the nut method. Also, make sure you use the really flexable tubing that comes with the tank instead of normal fuel tubing for the clunk. Normal tubing is too stiff to allow the clunk to move all over the tank.

DBCherry

My Feedback: (4)

Well, it sure sounds like the clunk would be the obvious solution, but I'm not convinced. With a full fuel line that engine should be able to idle for 20 seconds easily. That's an awfully long down line. Not to mention that forward acceleration in a dive, at least the first few seconds, would tend to keep the fuel at the back of the tank anyway.

I always use a piece of brass tubing in the tank to keep the clunk from falling forward, and I've never had an engine quit due to fuel starvation.
Dennis-

tailskid

My Feedback: (34)

Does it do the same thing while you hold it pointed downward?

Jerry

MHall

My Feedback: (7)

Sounds to me like your tank is loose and sliding forward and pinching off the lines with the weight of the fuel in it and the down line of your flight. As asked above, have you fired it up and held it pointed down to see what happens??[8D]

Carroll-RCU

My Feedback: (43)

I've had this happen to me on several engines and what is probably happening is your engine may be too rich and loading up on the down lines. Even gassers will die if too rich. Try leaning the engine out and see if that eliminates the dying.
Hope this solves your problem and let us know if this helps.
Carroll

bylandandair

Thank you for all your replies, its very strange, it happened again this weekend, only this time on a stall turn as the wing went over it instantly died, so it can't be the klunk because it died too fast even before the downline started. Maybe it's too rich? It runs fine during other manuevers, humpy bumps, half cuban eights etc..