Engine basics > Engine set up tips

Cox 049 poor run

(1/2) > >>

Pepper Kay:
Hi All:

Just mounted an  old 049 to a QTee for some fun flying and get a very poor engine run ...

Engine runs great on the stest stand ...

I note on the backplate, there is a small hole covered with a very fine mesh screen ... is that a breather of some sort ? ...

Were I to drill a hole in the firewall directly behind this hole in the backplate, would that improve the running ?? ...

Thanks,

Pepper
AMA # 3937

Tom Perry:
Pepper,

There should be planty of air reaching the intake if the engine is mounted properly.  Make sure the area that is recessed in the back plate is not block to insure good air flow.  To answer you origional question drilling the hole won't hurt but should not be necessary.

 #^

Pepper Kay:
Hi again:

One thing I forgot to mention is that I mounted the Cox directly onto a lite-ply former - it is solid ... the engine is not mounted on a Cox, Tatone or other engine mount ...

With that hole in the engine's backplate covered, I believe it to be causing the poor engine run, as it runs fine in the open air on the test stand ...

Thanks,

Pepper
AMA #3937

Ralph Wenzel (d):

--- Quote from: Pepper Kay on October 02, 2006, 08:12:38 AM ---Hi All:

Just mounted an  old 049 to a QTee for some fun flying and get a very poor engine run ...

Engine runs great on the stest stand ...

I note on the backplate, there is a small hole covered with a very fine mesh screen ... is that a breather of some sort ? ...

Were I to drill a hole in the firewall directly behind this hole in the backplate, would that improve the running ?? ...

Thanks,

Pepper
AMA # 3937

--- End quote ---

That "hole" is the engine's air intake; like the venturi on a "normal" engine. It's amazing that it runs at all with that blocked off!

Alan Hahn:
Pepper,
All of the Cox backplates that I have looked at have a relief cut into the backplate which will admit air into the venturi opening (which has the mesh cover to keep out pieces of grass and dirt). This even works when you mount the engine flush with a solid piece of wood.

I would venture that your poor running problems are probably coming from the reed--it may be sticking or not sealing to the tank, and cleaning this may be the best bet. However I warn you to take things apart over a white piece of paper so that you don't lose parts--especially the tiny rubber gasket that fits between the internal stack of the venturi and the inside of the backplate--next to the spraybar area. This is very tiny and can easily be lost. If it is left out, you will also experience poor running due to air leaks (and fuel, depending on how low the fuel level is) directly  into the downstream side of the venturi. It is easy to replace a lost gasket with a very fine slice of 1/2 A fuel tubing, but the best is not to lose the gasket in the first place!

Navigation

[0] Message Index

[#] Next page