Author Topic: gettin a cox to run (Read 8170 times)

Bootlegger · « **on:** August 21, 2015, 07:03:47 AM »

I have several 049 cox engines and have after run oil in them, when I try to get them to run, all they run is the prime.
These are all baby bee golden bee and black widow engines. What am I doing wrong?

Jim Roselle · « **Reply #1 on:** August 21, 2015, 07:47:08 AM »

This us full of great information:

https://dbabd7f0-a-62cb3a1a-s-sites.googlegroups.com/site/nitroengine/TheRevised2011GibeaultMouseRaceProgramv3.pdf?attachauth=ANoY7cp8pdoKUNqcqKhok5EUFE3hTQfaYk60QD-GgekEgNx76XOO_c-cDYSR6CferMfAHNWsOwSg83o4iDY8hX-qIVi-kI6jENBdMyrDQR0YpFMHzVUZn0Hxtg3bR17JTaLFWArxw_k8MA1qHFH4H-nk7VasefgswtEPPZXImL-ruxir4mM9x3W71V1CdWjjs-I2wCwMEhFBQ2LDSgbyJv83PsU1hPBlUAjtSZerzhGexen176kaCmR0FS3HLjsBUuJ1SudE2Cfq&attredirects=0

Ken Burdick · « **Reply #2 on:** August 21, 2015, 11:41:49 AM »

the reed is stuck. They sit around for awhile and get sticky. You may have to disassemble the engine or perhaps soak it in alcohol for some time to un-gum the thing.

mike londke · « **Reply #3 on:** August 21, 2015, 03:24:34 PM »

Clean the backplates too, I've had some that developed a green goo in them after sitting for years.

Phil Krankowski · « **Reply #4 on:** August 21, 2015, 06:45:51 PM »

Yank the needle and flush through the threaded hole with fuel. It might free things up enough to run clean, but if the fuel pickup is plugged it won't help.

Phil

edit: This is probably obvious, but the engine is going to be crazy flooded. Upend the plane and hand prop it gently, back and forth, until the excess fuel is done pouring out of the exhaust ports. Then the engine will be merely flooded. Clear the flood as normal then try it. This is also a good technique if you thing some seeds or dirt got sucked up at the field as it will often flush them right out and have you flying in minutes.

Trostle · « **Reply #5 on:** August 21, 2015, 11:58:51 PM »

Above are all good suggestions.

Another problem with these engines is that the seal of the backplate to the crankcase sometimes leak. If this happens, all the engine will do is run out the prime. It will not draw fuel.

You can check for a leak there by putting a drop of fuel on the area over the seal between the crankcase and the backplate. Turn the shaft. Counter clockwise, it will blow bubbles. Clockwise, it will suck the fuel in. Check on each of the four quadrants. If it is leaking, reset the seal. There is a way to hone the face between the tank/backplate and the crankcase. Maybe you can figure it out.

If there is a leak, you might get by just by resetting the backplate bolts, but be careful, the threads in the crankcase can be easily stripped.

If here is no leak, then reset the reed valve and/or clean the venture/needle assembly.

Keith

Wayne Collier · « **Reply #6 on:** August 22, 2015, 04:27:17 AM »

I usually use a super thin film of blue rtv between the crankcase and tank along with a slight amount between tank and backplate. Have used a dab on the screws as well. I then let the engine sit on a shelf for two weeks before adding fuel. Requires patience but a good seal pays off. Of course it's meaningless unless the reed, internal seal, and fuel pick up are in good shape.

David Fountain · « **Reply #7 on:** August 22, 2015, 09:41:14 AM »

It's a good idea to surface the back of the crankcase on all reedies, this is due to small burrs at the screw holes. Surfacing the crankcase is easy all you need is a piece of glass and a small sheet of 800-1000 wet/dry sand paper. Tear down the engine including removing the piston/cylinder set then lay the sheet of sandpaper on the glass (Has to be a true surface) and using a little light oil face the back of the crankcase in a swirling motion checking for smoothness in between. It doesn't take much this will remove the burrs and true up the back of the crankcase so the tank and gasket will seal properly against the crankcase. Once satisfied, clean it thoroughly and reassemble. As mentioned above it is a good idea to seal the screws to the back plate too. I know this has been mentioned too but but it don't hurt to say it again, make sure the pickup tube (clean the little spring in the pickup tube too and don't forget to reinstall it) along with the NV and back plate are clean. Another thing to check is the little O-ring that seals the venturi to the back plate. Get a leak there, it will run ok till half the tank is consumed and then the run will become erratic, needle will jump all over the place and may even quit and refuse to start back up so it's a good idea to replace it when you take it apart. They are cheap and easy to make. Also as everyone else has said Make sure the reed is clean and not sticking. if its a clip type after cleaning the reed make sure the clip is installed with the tang pointing out and check to make sure it's free to move. You can check it's operation by the suck/blow test should be able blow air through it but not pull. Hope this helps (David)

Ken Burdick · « **Reply #8 on:** August 24, 2015, 09:43:12 AM »

it's amazing where and how some of these engines leak from. It is not why yours won't run, but all good advice. The wido-satan article in Flying lines details all the combinations of tank and backplate I tried to get one to seal. Once sealed, I don't think I will ever disassemble it again!

K

Tim Wescott · « **Reply #9 on:** August 24, 2015, 10:21:43 AM »

I'm probably repeating something that's already been said, but -- clean clean clean. Then clean again. Whoever said your reeds are stuck is probably right -- disassemble, clean the reeds, and try again.

These motors can fly wonderfully when you take care of them, but a grain of dust that's nothing to a 35 is a boulder to an 049.

Paul Smith · « **Reply #10 on:** August 24, 2015, 03:56:16 PM »

Get about eight of them and bench 'em all. Put the best ones on the planes and the seconds in the spare bag. This MIGHT work, but not guaranteed.

Bootlegger · « **Reply #11 on:** September 29, 2015, 02:10:51 PM »

Thanks for all the reply's gent's, I got a chance to do some work on a couple of them today, and need the cox contact point to get some parts, so if someone can provide that cox contact point it sure will help.
Again thanks a lot...

Tim Wescott · « **Reply #12 on:** September 29, 2015, 02:25:58 PM »

http://coxengines.ca/

Or just remember to Google "Cox International".

Larrys4227 · « **Reply #13 on:** September 29, 2015, 02:44:18 PM »

..... or as another choice, you can try ....

http://www.exmodelengines.com/

They are USA based, but to be honest, Bernie in Canada has always had what I wanted so I go there.

Bootlegger · « **Reply #14 on:** September 30, 2015, 04:53:11 AM »

Mr Fountain,
What are you using to make the "O" ring for the engine, and where can it be gotten?
Thanks a lot

Bootlegger · « **Reply #15 on:** September 30, 2015, 04:56:16 AM »

I also need advice/suggestions as to which reed to use. I have heard that the stainless steal one is best, also can you hear the reed "flexing" when you flip the prop?
Again thanks

Fredvon4 · « **Reply #16 on:** September 30, 2015, 08:31:23 AM »

Te "O" ring can be sliced off the end of small fuel tubing with a razor blade...takes some luck and practice..out of 10 slices I end up with about 4 that are correct width and squareness. I cut about 50 and put all the good ones in a bag for later

I have gotten a fair selection of EACH of the different reeds from Bernie. Each has a different thickness and depending on the reed holder some are better than others.

Under Cox quality control was pretty good and the distance from the reed holder to the face of the venturi was consistent as was the diameter of the wire used to make the retaining clip.

Under Estes this is NOT TRUE. Thus for some combinations a particular reed may be too thick and not move freely

Also there are limits to max RPM of each of the different materials, so if you were competing in a MAX RPM contest one reed may be a LOT better than another (requires experimenting)

An a final thought....the face of the venturi opening has a very slight lip (look closely with a loop) than can be worn down and when this happens you need a new part. My experience is the steel reeds only work well on a new holder with a sharp and well defined LIP

Larry Renger · « **Reply #17 on:** September 30, 2015, 08:38:23 AM »

Reeds float away from and back to the sealing surface. They should not flex. That said, the old system used on the Space Bug and Thermal Hopper did flex as does the reed on a Dyna Jet.

Jim Roselle · « **Reply #18 on:** September 30, 2015, 10:56:13 AM »

I like the Mylar reeds. You can get upward of 21k rpm with no float.

Mark Mc · « **Reply #19 on:** September 30, 2015, 06:15:49 PM »

Quote from: Larry Renger on September 30, 2015, 08:38:23 AM

Reeds float away from and back to the sealing surface. They should not flex. That said, the old system used on the Space Bug and Thermal Hopper did flex as does the reed on a Dyna Jet.

Larry, you seem like the person to ask this question. Why did the Thermal Hopper and Space Bug use dual reeds? I recently got a Thermal Hopper and want to know more about the reeds before I disassemble it.

Mark

David Fountain · « **Reply #20 on:** September 30, 2015, 07:13:22 PM »

Quote from: Bootlegger on September 30, 2015, 04:53:11 AM

Mr Fountain,
What are you using to make the "O" ring for the engine, and where can it be gotten?
Thanks a lot

Sorry it took a while apologies, anyway as Fredvon4 has stated you can make them using small fuel tubing. Make them as he said and you'll be set!
(David)

Phil Krankowski · « **Reply #21 on:** September 30, 2015, 10:44:01 PM »

Some aluminum safe sealant is also your friend. Put some on the mating surfaces at the case. Put some in the rim of the tank. Put some under the screw heads, and maybe on top of the screw heads too.

Any auto parts store will have aluminum safe sealant. Regular RTV or silicone caulk is acidic and will eventually damage the thin parts of the engine.

Phil

Fredvon4 · « **Reply #22 on:** October 01, 2015, 12:46:41 PM »

ON a Cox Reed tank to Back plate- there is a small raised section on the tank back and on the perimeter mating surface of the tank a very shallow groove...some folks saliva wet a cotton thread to add in the groove, I personally use Permatex Anaerobic gasket maker as it seems fuel proof and doesn't react to the aluminum or plastic and will not set hard and glue the pieces together

I also us a 2/56 bottoming tap to chase two extra threads into the case after surface facing the back of the case on 600 grit and oil as suggested above to remove the original raised burrs from the drilling of the 4 holes

Reason...Cox had an exact screw length..Estes and other sources are not true length and some too long... There is plenty of depth remaining in the holes and by adding a deeper hole I don't worry about false tightening and always get a good tank to back plate seal.

The Du Bro Cat No 360 2/56 tap and drill is NOT a bottoming tap...I just grind off the lead in tip and have a bottoming tap that works just fine...much cheaper than the shipping cost of the real tap from Grainger etc

The 4 tank to case screws get a twist of cotton from a Q-Tip, about a 0.5 inch long, turned clockwise near the head of the screw...not very much just enough to foul the threads in the tank back plate hole

I only go to all this trouble sealing up the bugger after I have tested three or four reeds and get a run I like.... I also only use Air Tool oil as my after run and then just a little, and only after I have run pharmacy isopropyl 70% or 91% through the engine to dilute and remove any un-burned castor fuel

I have many old rebuilt reeds, Black widows and Baby Bees, that have sat for a decade now. I can confidently take them off the shelf today and flush one time with the 91% alcohol , fuel up with Sig 25% N and fire up first or second spring start

Larry Renger · « **Reply #23 on:** October 04, 2015, 04:18:45 AM »

I don't know why the Thermal Hopper reeds were designed that way. It is well before my time. I do know they run really, really well! Also, they are a bear to assemble, so leave them alone if you can.

Bootlegger · « **Reply #24 on:** October 14, 2015, 10:56:55 AM »

Got another question, what is a good to prepare one for storage? If using after run what is a good way to "purge" the engine for the next use?
I am not famuilar with these engines as these posts indicate.

Again thanks for all the help...

Phil Krankowski · « **Reply #25 on:** October 14, 2015, 01:33:28 PM »

If you are using it weekly, even monthly, then after run is not necessary. The fuel contains suitable oil for short term protection.

For putting it up for longer term you have choices from ATF and light motor oil, various air tool oils - but avoid the ones marked "non flammable" or similar as the engine won't start till cleaned because of the additives, to "after run oil" that various purveyors sell.

As for how to add it to the engine there are several different ways. Using a syringe with some tubing on it to push some into the threaded hole left when removing the needle is my choice on bee engines. Typically this both floods the crank case and pushes fuel out of the line and into the fuel tank. Flip the engine through (carefully since it will probably lock) to distribute the oil and wipe up excess oil.

TD's get oil added through the intake like on bigger engines.

Oil and exhaust is the hardest on paint after several weeks compared to a few hours of fuel so clean the exterior of the model well.

Flush the engine and tank with fuel to have it ready to run. The first tank of fuel will not run well, so consider wasting it and do a ground run with the second tank of fuel.

Phil

Author Topic: gettin a cox to run (Read 8170 times)

Jim Roselle

Jim Roselle