ge01734

Hi,
I have a COX .049 engine in my airplane, but I've run out of fuel for the plane. I have other fuel that I use for my RC Car, which is Wildcat's 18% oil and 15% nitro. My question is it okay to use this fuel on my Cox .049 engine?

Thanks

shoko1

Hi
Dont Use 100% Syntethic Oil To The Cox, Use 100% Castor or blend of the oils.
use 10-15% nitro and more than 16% Oil.
18% Oil And 15% Nitro Will Be Great... If its not 100% Syntethic Blend.
Good Luck, Excellent Engine.

ge01734

Thanks Shoko1, really appreciate the help.
Have a merry XMAS.

downunder

Just in case you weren't aware of it, the reason you need castor in these engines is because of the way the conrod is attached to the piston. They don't use a wristpin but have a steel conrod permanently attached to the piston by a ball and socket arrangement which allows the piston to rotate as it's running. Castor stays inside this ball and socket while synthetics tend to get squeezed out.

shoko1

Thanks downunder... I Didnt Knew That.

Bax

My Feedback: (11)

Hmmm. The current specification on Cox engines is a fuel with at least 20% nitro. An excellent fuel for the 1/2-A and smaller Cox engines would be 22%-25% castor and 30% nitro with the rest methanol. They'll run excellently on this blend, giving you good power and longevity.

gfurr1

Interesting information.

Bill, do you know where to get a fuel with the percentages of Nitro and Castor that you suggest? I am especially interested in mail order. I understand the cost of shipping for gallon size containers but I don't have a choice here.

Thanks,
Glynn ..

gocartdude

Hi
IS there someone who can tell me why we dont break in cox 0.049 engines and about castor ,can i make it bymyself at home?

MJD

My Feedback: (1)

Ditto that. I never had any joy with fuels below 15% nitro in Cox .049 engines (neglecting the Texaco as it doesn't apply to 99%+ of questions regarding Cox .049's). Below that you can tell they are just begging for more. Yes, you can get an .049 to run on 10% but the needle is more finicky and it just isn't content, so why bother for the few cc it takes per run? 20-25% makes them much happier. IIRC the Cox brand fuels are 22% castor? You'll be okay with a 20% oil, syn/cas blend if that's what you have available locally. Or pick up some 16-18% oil syn/cas blend and add castor to it to bring total oil up to about 22%. As everyone has said, don't run straight synthetic.

If/when you run an .020 or .010, run 25%-35% nitromethane, 25% minimum, same deal on oil. An .010 will barely keep running on 15% nitro.

MJD

loughbd

Cox made two fuels. "Blue can" and "Red can". The blue was the regular sport fuel and was 25% nitro. The red was their racing fuel and was 35% nitro. Both were 20% castor oil. Small engines give off their heat very quickly and heat is power. Cox engines, and most small engines, are most happy on high nitro fuels to keep the heat up. They will run on 10/15% but not up to their potential. As far as the ball and socket connecting rod, synthetic won't hurt the joint. They all loosen up eventually. Cox and K&K make a special little reset tool to solve that problem. You only have to do it once. Seems like the joint gets work hardened and doesn't loosen again.

I acquired about 15 gallons of Cox fuel (both kinds) awhile back. It's all in pint cans. runs great in the YS 4 cycles but it's a pain digging the little filler cap out of each can and pouring it into a gallon can.

car54

100% synthetic blend? If it was 100% synthetic, it wouldnt be a blend, correct?

Jim Thomerson

Cox engines don't need much break in because of the precision with which they are made. They are in fact little jewels.

gocartdude

ok guys breakin in cox means to run it rich for 2 tanks than lean it a little bit about the fuel i think its better to run 25%oil 80% castor 20%syn i have castor oil used for hair, is it good ?

loughbd

Cox instruction sheets say to run the engine for ONE MINUTE rich annd then lean it out. 15% nitro is a little on the low side. Cox sport fuel (blue can) is 25% nitro and the racing fuel (red can) is 35% nitro. The little engines lose their heat very quickly and the high nitro keeps them hot. They run 100% better on high nitro fuel. 20% oil is perfectly fine. Itis the oil content of Cox fuels and it's all castor.

downunder

What Jim said. I read the other day where someone said they were made to a tolerance of 25 millionths of an inch which is pretty much what I'd heard years ago. They had to do this because they were pumping out engines in the thousands every day and they couldn't afford to have anyone hand fitting pistons to cylinders or giving a final hand lap as Enya used to do. So any .049 piston would fit perfectly in any.049 cylinder. This can't even be done today on the much vaunted CNC machining with much larger engines where fits aren't as critical. Because of this precision Cox said a one minute rich run was all that was needed to finish settling in all the parts.

loughbd

That's exactly what Cox said in all their paperwork and what the writers said about Cox engines

loughbd

That someone was me

MJD

My Feedback: (1)

The honing machines used for that process are worth a king's ransom. The tolerances that can be held are phenominal. MJD

loughbd

That machinery is all in China now. That's where Estes is having the Cox stuff made. One of these days you will find "made in China" on a Cadillac.

richrd

Odd no one mentioned SIG Champion fuel …. it’s everywhere … also with lots of caster, too much for most people in sport flying. My favorite for the Cox .049 is their 35 % nitro makes it start easier so my son can learn to fly not whine. BTW champion 10 % is my break in fuel.
Rich

loughbd

What is your definition of everywhere?? Sheldon's doesn't carry it. Hobby People never carried it, Tower doesn't carry it and I have never seen it at any local hobby shop.

cjoshua2

I HAVE AN OLD PT-19 FLIGHT TRAINER THE ENGINE SEEMS TO KINDA STIFF IS THERE SOMETHING I CAN DO TO TRY TO LUBE IT

culver

I may get sniped at for saying this but I would squirt a little fuel into my engines when they would gum up in storage. let it soak in a little before trying to turn the engine over then disassemble and soak the parts in fuel, rubbing alcohol or methanol if you have it. I used drug store rubbing alcohol as a kid because it was always there in the med. cabinet.

roxley

Hi,
I have a Cox 049 that has a standard connecting rod and a wrist pin in the piston. I know this because I just had to make a replacement after the rod end broke off from the rod at the piston end. This must be an oldie, right?
Randy

downunder

I'm no expert on the Cox engines but the only one I've ever heard of that had a normal wrist pin was a special 15 which surprisingly was called the Special .15 . Maybe Cox tried it in their smaller engines at one time but if so then I'd say it'd be very rare.