I have a 61 TT mounted inverted in a world models chipmunk. Siphon is my problem. It does not matter of the plane is right side up or upside down. If the plane is right side up the problem is much worse. I am thinking the only thing I can do is mount it sideways, but I will not be able to use the stock muffler. Any ideas of what muffler to use or how to correct the siphon problem. I can not move the tank easily. It is an ARF and I would have to take the front of it apart


Thanks for any info!!

Scott

get the dremel out seems u need to relocate the fuel tank

I have the same problem in a GP Venus 40 with an inverted Saito 72. There is really no way to lower the fuel tank without compromising the airframe. My solution was to cut a couple of holes in the side of the cowl and run the fuel line out and back in. from there I can crimp the line so fuel doesn't fill up the carb (you have to be careful about a hydro-lock condition on the Saitos. I simply remove the crimp before starting. The siphon actually makes it easier to prime. Once it's running, the mild siphon is not an issue.

Jason

If you have a siphon problem both up right and inverted, then side mounting the engine will not resolve anything. You will still have a siphon problem. Personally, I don't think moving the tank will help no matter (and I cannot imagine how you can have a tank placement related siphon problem both upright and inverted anyway) what since flipping the airplane upside down will lower the tank a huge amount already.

My suggestion would be to put a hemostat on the fuel line to the carb until you can find the real reason for a up right AND inverted siphon problem.

John

The problem with hemostat's is that they can sometimes cut the fuel tubing and the chances are greater the longer you have to do it.

Randy

I've used smooth jawed hemostats on many models for a very long time without a problem. Use a high quality fuel line, like Prather, and you won't have a problem.

Besides, the fact remains, there is something wrong besides the tank placement if it siphons both upright and inverted.

John

If the carb is exactly at the center of the fuel tank then it will siphon regardless of whether it's upside down or right side up since a full tank will place the fluid level above the carb in all orientations around the axis. However, the force of the siphon should be minimal.

Jason

Jason,
I didn't think of that since I have never seen a kit, especially an ARF build out this way, but you are correct. In this case, sidemounting the engine as suggested in the first post will not solve anything. The builder is going to need to move the tank.

John

I think I have the answer to your problem. A lot of guys fill the fuel tank quite a while before they start their engine. Don't fill the fuel tank untill you are ready to start the engine. Then don't choke the engine. If the engine is inverted turning the engine over with the electric starter will prime and start the engine all in one step. If you fill the tank and then let the plane sit for a few minutes or longer the fuel will siphon into the carburetor.

I use a Du-bro filler valve to solve this problem, when the filler tube is plugged in, the fuel is cut off to the carborator. Just fill and leave the fill tube plugged in until you get ready to start the engine.

James