Needle Setting For Cox Engine With Fine Thread Needle

Yep. I have one in an .049 with a postage stamp backplate and it likes to start at 7 turns and run at 6 1/4.

Greg

Thank you. I will be heading out shortly to give it a run.

If I was onomatopoetic, I would write my phonetic interpretation of what too rich and too lean sounds like... but I'm sure you already know, so that will save me from entertaining you. Like humming a few bars... aw heck, here goes:
wwwwwwwwwwAAP >That's too lean.


BLRPITYPRPRPBLEPITYP >That's too rich

And in case anyone wondered, the above noises that imitate, well, anything, is known in the English language as "Onomatopoeia."  pronounced: [Ah na mah ta peeya]

No kidding.
Rusty

Ok. I just got back in. I mounted the engine and it went brrrraaaaaap right away. I was happy. Then I hooked up my balloon tank that I have used in the past so I know it is a good working balloon tank. Then it all started going south. I could not get it to run. The best I could do was get it to BLRPITYPRPRPBLEPITYP, over and over again. So, I removed the tank, tightened the needle and ran the excess fuel out. Started over. A drop or two alongside the closed piston then it ran a brief second. Did this multiple times. All good. Adjusted the needle 4 turns out. Hooked up the fuel balloon again. and fuel started literally pouring out of the cylinder. Removed tank, flipped till clear and excess fuel was burnt off. Tightened the needle to 3 turns overall. Tried again and it ran for about 30 seconds. Restarted it and it went BLRPITYPRPRPBLEPITYP multiple times. As it was doing this, I noticed fuel bubbles coming out between the front of the crankcase and the driveplate. Also at this time again, it started coming out of the exhaust ports. Tightened up the needle a turn or so, and flipped it a bit and it fired and ran again for about 30 seconds then died as fast as it started. So, after all this, I cleaned the engine up and am thinking of disassembling it to check the reed valve as this is my suspect to the flooding. If anyone here thinks this may be a good start, I will do so, but I am also open to other ideas. I may have a bit of time tomorrow evening, if I am home, and if not, Sunday it will be. But overall, I was happy to hear it run for a short bit, and after a bit more tinkering around, I think she will be ready to go.

If the next test runs go the same, I will look online for a different tank, probably something like a 'Perfect' type tank in a wedge style for control line. But I do have faith I will get it going this weekend.

Chancey,

I didn't install a new reed as the one inside looked ok, it's a copper reed though and it has age on it. I probably should have run it up, but I figured you would want to break it in.

Ron

Unless you're over priming, it can't be getting flooded if the tank is at the right height. Pull the line off the engine and hold it at the center height of the backplate(where the spray hole is. Raise the tank until the fuel stops coming out of the line.

Alternately, if it's too high and running freely into the engine, clamp the line until you get it running good on a prime and unclamp it quickly to feed the engine. If it quits, clamp it quick, dry it out if needed, adjust the needle slightly and try again. if nothing is wrong, it will run. If fuel is profusely running out through the nose, you may not have any crankcase pressure or vacuum if it's got a hogged out nose bearing. In that case the case is shot.
Rusty

I did take it apart and looked at the reed. I did not remove it as it looked nice and in very good condition, same as you had mentioned. As well, I did a suck and blow test on it by wrappng my lips over top of the reed and retainer side of things. It did not appear to function oddly, so my first guess of reed being suspect is busted! But I also had my first taste of glow. Not bad, but needs mix. that will teach me to clean things properly before testing again.

As for the tank. I had my balloon tank slightly below the air intake when all that 'magic' happened. It did its best running with the tank held above the intake like a gravity feed. As for fuel out the nose, it was not running or pouring out, but rather bubbling like when the head is loose. I will just keep trying until I get it. Thanks for the help and suggestions, and I will keep plugging at them.

New, I think you said you didn't have another tank , but if you do I would try running it in on something that you know works before attempting the balloon , that way you know it runs fine and all you will need to do is get the positioning right of the balloon tank . Even if you just set it up with a dripper to test . Eric

Thanks. I will set up a syringe on a stick without a plunger in it. This will be the next test for me, but will have to wait until tomorrow evening at the earliest. Got a model airplane airshow to get to tomorrow morning. Hopefully the predicted severe storms hold out till the evening.

akjgardner wrote:
Ah na mah ta peeya......Hey that's a John Prine song

Is it. I didn't remember that one. Maybe I should sit back for a while with an Illegal Smile and listen to an old John Prine record. Maybe catch up on Dear Abby.

Song, or no song, your interpretation and spelling of the sounds are pretty much bang-on. Now that is cool. And now, I am going to have to search the song mentioned and listen to it.

Ok, so I found your song and had a little laugh.
And now, I just got back in from the garage before heading to bed, but I had a chance to hook up my engine to its stand and take a picture for you to see.  I have used this set-up before and it had worked on my other engine with the same syringe and fuel line.  Anyways I anticipate getting this engine running steady by the end of the weekend.

You will flood the engine with the open syringe that high.

The syringe should be at a similar level to the venturi, so it will not need to draw air on prime, yet will not flood.

Phil

pkrankow wrote:You will flood the engine with the open syringe that high.  

The syringe should be at a similar level to the venturi, so it will not need to draw air on prime, yet will not flood.

Phil

When you say similar level, are you referring to the height of the bottom tip of the syringe where my fuel line attaches?

At the level where it doesn't gravity siphon into the engine. Unplug the fuel line and hold it right at the nipple on the engine, and lower the fueled syringe until it stops dribbling out of the line. Secure the syringe there. That height will vary with the amount of fuel in the syringe, so mark it and use the same amount every time you crank it. If you used a regular fuel tank, a clunk or wedge, it would be easier to setup.

Don't you have a starter spring you can put on it? That would make it a whole lot easier to crank. If not, a 6" prop would help too. Looks like you might have a 5" on it now.
Rusty

Here's a home improvement explanation.
http://www.factsfacts.com/MyHomeRepair/WaterLevel.htm

(I used a short clear section of 1/2 inch that I put on a garden hose when I last needed a level like this. The clear section was on a wash sink, and is around 3 ft long. But I digress.)

The top of the fuel level in the syringe is the concern. If you have a piece of material that can make your support apparatus hang off the table edge so you can adjust up and down all the way above or below the engine you will be fine. Once the engine is running having the fuel over or under by up to an inch is going to be fine on the bench.

Phil

Ok. So I got tied up this weekend and was out of town all weekend. Yesterday was also a wash. But today was the day. I had a bit of time so I went at it with this engine yet again. I heeded the warnings and positioned the syringe at the correct level. I filled it and then primed the engine. I robbed a used spring zero-drag spinner and installed it just for ease of use. Well, after filling the syringe, I dabbled 1 drop on the side of the piston, and it fired right up. Ran for about 30 seconds then bogged down, then did the rough run again. I stopped it by pinching the spinner. Adjusted the needle and tried again. Fired right up and ran briefly again. It seemed to keep going rich, lean, etc. That is when I noticed that the fine thread needle kept adjusting itself. I tried a piece of fuel line on the whole needle to prevent this, and it slowed it down, but it still does do it. As for runs, it seemed to use up most of the syringe then dies out. Fill it, it fires up runs approximately 20-30 seconds and dies. So, now that I have this thing starting easier and mounted on a similar plane that it will be permanently mounted on, I will revisit my balloon tank hopefully tomorrow and try it yet again.

Does anybody have any tips that may work to keep the needle valve in place? Would fuel line length be a contributing factor? Best runs were achieved at 2 3/4 - 3 1-2 turns out on the needle. Does this also sound right? Thank you.

What fuel?
how many shims/head gaskets?
what prop?

Phil

Sorry, forgot to mention the details.
Sig Champion 15% fuel
TD Glowhead with 1 shim
Cox 5 x 3 prop, black and no safety tips.

And if it makes a difference, here is a complete engine breakdown:
TD Glowhead
Red horseshoe backplate with fine thread needle valve, copper star reed with e-clip
Black Widow Crankcase, and assuming matching crank
Sure Start Piston and cylinder
Aluminum spinner
Cox 5 x 3 Black propeller without safety tips
And now a Zero-Drag spring starter (not in picture)

Try loosening the prop and turning it 1/2 turn. It is a "rubber ducky" and cannot be truly balanced.

I think you are over compressed with the TD head and single gasket. Try 2 or even 3 gaskets with the 15% fuel. Don't be afraid of going up to 5 gaskets, but I doubt that many will help unless you increase your nitro content.

The prop screw you are using is a soft metal. Consider replacing it with a harder socket headed cap screw.
http://coxengines.ca/cox-.049-propeller-screw-socket-long-black-2.html
The black screw is much more resistant to bending.

Phil

Ok, thank you for the advice. I will borrow a standard head gasket from my other engine and give it a try. And even possibly try a standard head as well. I will flip the prop also. Anything is worth a shot. This is how to learn more about these little guys. I will also be switching my fuel to Sidewinder as I finished up my Sig fuel. Now will be at around 18% nitro with my added castor.