Electric3D

Just got hold of an old COX Texaco 049 with organge tank. Cleaned it up. On the first flick it roared fine. But having issues with keeping it run continously rather then just on prime. So kept opening up the needle valve. I have opened it up to 5 full turns but will not run continously.Runs only on prime. Further opening of nedle valve floods it. I have still got the original fuel tube at the back that has got real hard. Can you please suggest what repairs are to be warrented to make it run. I am using the same 1/2A Norvel Fuel 25% Niro with mixed in castor. My Sure start 049 and Cox TED 051 run great on this fuel so it is not that. Plus the plastic backplate does not have a filter wire mesh circle, but is open. Any suggestions are highly appreciated. Thanks in Advance.

Andrew

Old probably describes your problem. The engine apparently cranks easily and runs on prime. Being old, it's likely that you have gummed castor in the intake venturi or needle valve seat. Remove the needle valve and add raw fuel to the hole and into the venturi to help dissolve any remaining castor oil. If the pickup tube has hardened - I've seen some that you could drive nails with - then replace it with a piece of silicone fuel tubing. The anti-kink spring can be added or left out. Sometimes the tubing gets so hard that it won't seal and you can suck air where it slips over the nipple on the backplate. Check the venturi tube gasket to see if it has hardened over time, is mis-shapened or missing. That single gasket can cause more aggrevation than anything else. Also check your reed for cleanliness and free movement and to be sure there is no gummed castor under it or stuck to the reed seal.

If the regulars here can't get you up and running, then you're probably out of luck.

andrew

Electric3D

Hi Andrew,

The reed is very very clean. The venturi holes are very clean. I took the engine apart except for the cylinder and soaked it for couple days in an old fuel. before soaking, the full engine was hard as stone, piston would not move at all. The gas hardened tube , i will replace with Silicone tube but how excatly is it to be positioned inside. As far as the black O-ring goes, I could replace it. It ihas not deformed or swelled but was a bit fragile to touch.Any photo out there as to how the fuel tube is to be positioned for cL and for RC ? Different locations ? Cheers.

BMatthews

The needle valve can be plugged by old dried castor and even soaking it won't clean it out. Swap the fuel pickup tube as mentioned above and also force feed fuel from a syringe or bottle through the line and ensure that with the needle valve open a few turns that a small jet comes out the small hole in the venturi of the backplate. If no fuel then that's your problem. And hopefully when you soaked it and blew out all the crud you had the needle valve fully removed.

Check the reed for sealing. You can do this by using some medium size fuel tube on the tank bell's passage. Stick the tube onto the part that fits into the backplate. Now ever so gently blow forward and ensure that the reed opens easily. Then draw back ever so gently and ensure that it seals. The amount of pressure you get by keeping your nasal passages open while both blowing and sucking shoudl be more than enough to test the reed. If it fails either direction then something needs to be done.

The only other possible issue is having a good fit between the tank bell and crankcase. No burrs or other issues with fitting easily and tightly. Then check the crankcase to tank gasket to ensure there's no split or other issues. If the crankcase can't seal it won't generate the suction needed to draw sufficient air and fuel into the case for the engine to run. In all of these issues from needle to case gasket they need to be perfect. "Close enough" typically never is when it comes to small engines.

BMatthews

By the way, this is a good topic when it comes to Cox engines in particular and small engines in general. Once we're done and you're running correctly I'm going to cut n' paste the better replies to the Cox FAQ.

R/C Phile

I second comments on the Needle Valve and Tank sealing. I had issues where my Black Widows started and ran well (For a while) but were not consistent throughout the whole tank and / or were mis-firing / running unevenly through maneuvers, especially when running inverted.

It turns out this was mostly related to fuel line / tank / Needle Valve sealing / and making sure the reed was fresh and without any foreign matter in the retainer area. (A little piece of dried grass in the wrong spot will just wreak havoc)

Making sure the plug is fresh and the head is tight / stays tight makes a big difference too. If the head keeps getting loose, replace the brass "O" ring.

Just in case this is not already in the FAQ (Bernie may have it posted elsewhere if I remember correctly) I followed the instructions shown here (It tells you exactly how to seal properly and how to correctly position the fuel line:

[link=http://xenalook.com/?id=696654&page=blogComments&blogId=117793]Gibeault Mouse Racing Program[/link]

All that transformed those engines. With increased consistency , I was able to "dial-in" the needle by very fine increments over several flights and once I got it "on the money". I practically never had to touch the needle valve again.. Easy one flip Starts and flight after flight consistency..

Even if you don't run the engine competitively or though inverted maneuvers, it's worth doing just for the consistency and the "set and forget" running , the hour or so spent on the mods more than repay for itsellf with the instant starts / no fiddling / and increased flight time.

Electric3D

Thankyou all. I will defintely do that. Thanks for the link. I might just bite the bullet and order these things :

1) http://coxengines.ca/product.php?pro...28&cat=0&page=
2) http://coxengines.ca/product.php?pro...&cat=25&page=1

3) http://coxengines.ca/product.php?pro...&cat=25&page=3

The spring looks like it needs to be replaced, quite loose.

Witha syringe and needle valve open, some fuel can easily be forced out from the hole in back of the tank plate. Gasket between tank and engine looks good. I am tavelling on business, so weekend I will try everything once again and report back.

Cheers and thanks for all your assistance.



______
Fixed link... bmatthews

BMatthews

That link in item 2 isn't the correct needlevalve and spring for the Texaco engine. What you want is this needlevalve and spring;
http://coxengines.ca/product.php?pro...&cat=25&page=5

or just the pack of three springs;
http://coxengines.ca/product.php?pro...&cat=25&page=5

But what I do for Texaco style running is to replace the spring with a washer that fits over the needlevalve (a small one filed out to fit) and a length of medium size silicone fuel tubing cut to fit so that it produces a nice tubing "spring" over the needlevalve at the same time that it forms a nice air seal to avoid air being sucked down past the needlevalve threads. You want to cut it so that it makes contact about 6 turns out and squishes down the rest of the way.

cfircav8r

My Feedback: (1)

I would still replace the reed, because although it is clean it is old and nitro will attack the plastic over time making it loose its flexibility and elasticity. they are cheap and easy to replace

Electric3D

Thanks. I will order the correct one now and change the reed too.

Andrew

E3D

If you're going to order a needle and reed, I would suggest that you go ahead and get an overhaul kit. You will be able to replace most of the parts that are prone to wear, hardening or taking set. A pic is in the attachment. However, I still prefer silcone tubing over the clear tygon.

andrew

Electric3D

Finally did all the changes and gave it a shot. Now then it started to give 10 seconds Baarps. versus the 2 to 5 seconds. Still would not run continously. Re opened and found that the back plate Nipple inside where the back plate screw goes in was shakey. Touched it and it fell out. There it was sucking air. Replaced it with another much older but intact back plate. Now it runs continously.

However the needle valve and spring that were replaced do not hold the RPM. It roars and sags. On and on. Cannot get a constant power. The fuel is good as it runs my other cox engines. Finding it very difficult to hold the needle valve setting. It roars as I rich it and a bit back off on the needle valve to lean it just a bit, it will sag. So on goes the roar and sag.

I am out of ideas now. Appreciate in advance all of the inputs to now hold the needle valve setting.

BMatthews

What prop are you running with the engine? Also if you're using a Texaco head be aware that it likely has a lower compression ratio to optimize it for running with the typical bigger and slower revving props. Can someone confirm if this is the case with the Texaco heads or am I mis-remembering this? If the head is an issue going back to a regular head to run with small props and the usual high nitro fuels would be a solution. If the goal is to run with big props and reduced RPM then switch to a more moderate fuel such as 5 or 10% at most nitro which will run more evenly with the bigger props and matching lower compressin ratio.

Electric3D

Hi, I am running it on a 6 by 3 prop. Can Texaco JR handle a larger prop ? How big in terms of both dia and pitch ? Feels like a good compression, do I need dual gasket in my cylinder like my TD 051 ? Lost, Thanks for all the inputs.

PS : Is there a different Glow head for Texaco Jr. or Texaco in general. I am using one of the spare glow heads that I have. Original was burnt. I am sure these are Cox Babe bee, black widow, TD glow head etc.

hllywdb

E3d,
The TD (high compression) head will have casting marks all around the outside, like a sundial. The regular heads are un marked. With a 6x3 prop, you most likely only need 1 gasket. I used to run 3 (to lower the compression) when running larger props, like the 7 X 3 1/2.

The surging may be due to the older back plate. What needle are you using with that backplate? It sounds like it could be sucking air around the needle. Try BMathews trick of using the tubing over the needle instead of the spring on that backplate. Almost all cox motors run better that way. I even do that on my meddalions. The TD's I always replace the needle assy with a texas timers of KK one, which basically already have tubing around the needle.

combatpigg

My Feedback: (3)

A steady push against the piston at the correct time in it's travel will produce the most torque. Much more so than a sharp hammer blow, which happens with too much nitro and / or too much compression..and too some degree with too much prop working against too much nitro and compression.
Correct timing is essential...
Smaller props make these points less critical, larger props make these points [laws] very critical.
Besides controlling the burn rate and when peak combustion pressure occurs, the rest of the engine needs to be mechanically correct in order to make running a max load prop feasible.
If the engine is in good shape, your tuning tools are nitro %, compression, combustion chamber design and whittling on the target prop until you get what you want.
If the engine isn't acting right with a 6x3, no magic wand will make it run any better with a Texaco prop until the problem is figured out through trial and error sweat equity.

gcb

Electric3D,

Lets backtrack a bit...the Texaco and Texaco Jr are the same except the Jr. has a smaller tank. The Texaco is an engine designed to run a large prop (in the 7"-8" range). To accomplish this, a smaller than normal intake was used to maintain fuel draw at lower RPM. The glow head was like the standard plug except additional fin area was provided for extra cooling.

I have run mine on a 6x3, but don't expect a lot of RPM because of the small intake. Unsteady running is probably due to normal things, not because it is a Texaco Jr.

Assuming you have an air leak somewhere, I would first check around the needle. As mentined, you can use fuel tubing with, or instead of, the normal spring. I have also used blue Lok-Tite (not permanent seal) to seal the threads.

Next suspect the fuel pickup inside the tank...there may be a small leak. Also check the small gasket between the backplate and the venturi tube inside the tank.

Reed. Make sure it can flex/move and seal correctly.

Make sure the crankcase seals to the tank correctly. Some crankcases have been found to have a slight burr or ridge, This can be lapped flat so the gasket seals perfectly.

I'm sure you have already checked these, but a second look might help. There ain't no magic, just a lot to check.

George

SGC

How much running has the engine had previously? did you devarnish the piston/cylinder? The engine haveing been run and stored just needs a realy good clean!! and the noted common leaks fixed and it must run, your 25% fuel will be fine with a 6x3 but may need 2 head gsts.
Stewart

Electric3D

Thank you all. I am taking all your inputs and making a "To-DO" List. Step by Step i will do them all even if it is a repeat.

So far the new parts are : Reed, Fuel Pick Up tube, Back plate in good shape, Gasket between tank and engine ( Sqaure one), the o-ring at the venturi inTake and very clean engine , no varnish or build up in cylinder or piston. A glow plug that works. I will continue with same fuel (getting low) and 6 by 3 prop.

Replace spring with Fuel tubing . I have to try that. What is common for the length of the tube ? As big as the spring under compression ?

Next weekend is just a few days from now. Cannot wait.

Thank you all very much. Report soon back and let you know how it is going.

BMatthews

The tubing, along with the bigger washer to avoid the tubing popping over the too small needle valve "rim" should just begin to seal at around 5 to 6 turns out from closed. With it that long you can still easily run the needle valve in to fully closed.