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Fuel Question

Old 08-24-2003, 08:59 AM
  #1  
ranchpig
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Default Fuel Question

What do all the different %'s in fuels mean? Tower Hobbies has about 30 different kinds?

Also what exactly is "after run oil"?

thanks... and i did search the posts
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Old 08-24-2003, 10:02 AM
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Default Fuel Question

The % you see advertised is the %of Nitro in the fuel. Most engines run well on between 5 to 15 %nitro content. Check the engines manual for the reccomended Nitro.

After run oil is a protective measure to prevent your engine from rusting if it's going to sit for a while. Since methonol tends to draw moisture from the air. ( methonol is also an ingrediant if glow fuel.) A couple drops of after run oil after each day flying is a good habit to get into.
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Old 08-24-2003, 10:09 AM
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you go rookie!!!!!!
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Old 08-24-2003, 01:18 PM
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Steve Guinn
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Also, 18% oil content(80/20) would mean the fuel contains 18%oil, with 80% of this oil being synthetic and 20% being castor oil.

Use more than a few drops of after run oil.
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Old 08-24-2003, 05:00 PM
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ok... great... now i got 3 different engines. One's a fox 78 and the other two are .60 size but are in the plane and i can't see what make.... would a 10% fuel be alright? Do you just experiment, etc?

Also do you just pour the after run oil in the carb and spin the prop? Would reg. 10w30 work?
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Old 08-24-2003, 11:06 PM
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Default Fuel Question

10% nitro will be fine in those size engines i wouldn't use any more, you guys in the USA seem to use more nitro than most of the world probably due to the cheaper cost.

for oil i use pure castor but there is nothing wrong with mostly synthetic although about 2% castor can protect from lean run conditions, i dont use after run but i'm not sure if its recomended for sythetic oil fuels
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Old 08-24-2003, 11:21 PM
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Yuck! Yuck! Ditch the castor oil! Use 100$ synthetic and I garantee you'll have less cleanup.

Ranchpig, a lot of use b lend our own afterrun oil. I personally use a 50/50 blend of motor oil (any weight) and Marvel Mystery Oil.
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Old 08-24-2003, 11:22 PM
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Default Fuel Question

a couple drops of after run oil are useless. you need to put enough in that your engine smokes for a couple seconds after it starts, but is not hard to start. while methanol draws moisture in from the air, also nitromethane is extremely corrosive. after run oil will prevent it from corroding. what you want to do is drain the fuel from your tank when you are dome flying, RE CONNECT all the fuel lines, start it up and let it run until it stops. note, run it at about idle, because an idle can burn small amounts of fuel that wide open throttle can't. once it stops, pour the after-run in. a 3 oz bottle of that stuff should only last about a dozen trips to the field. a good way to do that is count out about 15 drops of oil, and put it in there. bring the throttle to wide open, make sure the glow plug is cold, and put your starter on it for a couple seconds or so. they say not to do that because of hydraulic lock, but it never happens. you can get after run oil for cheap. go to auto zone, and pick up a gallon of "marvyns mistery oil". it is the same thing. it is about $5 for a gallon of that stuff, while a 3 oz bottle costs $8. It is an anti-corodant. it works very well.
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Old 08-25-2003, 01:04 AM
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Default Fuel Question

The new guy is already stirring the pot by asking the dreaded after run oil question.

You will get many opinions about after run oil. Some folks, like me, never use it, don't have problems, and think it is a waste of time, money and effort. Others think putting an engine away without a good squirt of after run oil is flirting with disaster.

Eric
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Old 08-25-2003, 03:10 AM
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Hmmm... Pot stirrer ... I like that

Ok... well today i took apart the Fox 78 and the carb was totally stuck. Just so gummed up. Had a bugger of a time w. it. Took the head off and piston sleeve and tried to degrease all the carbon(?) build up. Put it back together but have not started it. Seems like good compression especially w/ gear oil as a lube LOL! j/k Funny design these motors are.

What do you all use to get the buildup off or do you leave it to help compression? I'm a gas guy and carb cleaner usually melts it right off but it was having a hard time disolving it.
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Old 08-25-2003, 04:54 AM
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I take the plug off and put about 5 drops down it and then I put about 5 drops down the carb and turn the engine over about 20 times to throughly coat everything.

But I only do that during the winter months when there is a lot of moisture in the air. It's pretty dry in the summer and i don't worry about it.
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Old 08-25-2003, 05:47 AM
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Default Fuel Question

My engine is an os46 and the manual says that after run oil should not be put through the carb because it will cause the rubber o-ring to deteriorate
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Old 08-25-2003, 01:14 PM
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Steve Guinn
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Default Fuel Question

I had the same question about my O.S. 46.

Went to the official O.S. frequently asked questions website and learned the true Japanese to English translation.....

Do not put after run oil in thru the fuel line to the carb. It is perfectly OK to put it in the carb.

Trust me on this one.
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Old 08-25-2003, 01:24 PM
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I'm using plain old type F automatic transmission fluid for after run oil. I give the engine a solid squirt down the carb throat and turn the engine over by hand several times. I also store my planes nose-down (there's another religious war coming on), and the oil eventually leaks out the front bearings, which I think is a good thing. When I've rusted bearings, it's always been the front bearing that went.

Nitro is cheaper in the US than the rest of the world as mentioned. I use 15% in pretty much everything. A bit of nitro really helps with engine idle and makes the needle valve less sensitive. I also noticed that the poster is in CO. If you are way above sea level, going to 15-20% nitro can give you some extra RPM that can be really useful that high over sealevel.
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Old 08-26-2003, 02:37 PM
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Default Fuel Question

A couple drops of after run oil after each day flying is a good habit to get into.
first of all , i think he was being general... not like only use like 3 drops.. second, it does NOTHING to totally flood the motor of oil.... just if you want to waste it....10 to 15 drops max is plenty. and it only takes 10 seconds to do. third, marvel mystery oil is 100% fine to put in thru the carb as it WILL NOT harm o rings.. hell you put it in your gas tank, tranny, just about anything and it doesnt hurt them.. and there is NOTHING wrong with a touch of castor in your oil mix.. yes its messier, but as stated.. if you botch a needle setting its not gonna hurt your motor for the most part.(just makes it ugly)
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Old 08-26-2003, 03:07 PM
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Ok...here we go.

Marvel Mystery Oil (henceforth known as MMO) does not have the rust inhibiting qualities of a good AIR TOOL oil.

It is the consensus of the RCU membership that MM air tool O (MMATO) be used (if using M&M).

MMO will gum things up, MMATO will not.

MMATO can be found at some auto parts stores.

It is my opinion to ALWAYS use some CASTOR oil unless you are an expert engine tuner with plenty of money and a perverse adversion to said oil.

There.
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Old 08-26-2003, 03:09 PM
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Default Fuel Question

they say in the carb, but what they mean is don't put it in behind the nedle valve, because it will eat away at some small part in there. putting it in the carburator is plenty fine and will not damage anything. Also, it is even more important not to put the after run oil in behind the needle valve if your engine is pumped like mine. Until it is all fluxhed away, it restricts the movenent of the regulator membrane and causes it to starve.
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Old 08-26-2003, 03:14 PM
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Default Fuel Question

you can use pure synthetic as long as your engine doesn't run too hot. Pure synthetic is fine for four strokes, but doesn't fare too well on a two stroke. a pure synthetic oil has a habbit of decomposing at around a two strokes opperating tempurature.
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Old 08-26-2003, 04:14 PM
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What do you all use to get the buildup off or do you leave it to help compression?
Yes. Clean up the wrong place and you will have no compression.
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Old 08-26-2003, 05:29 PM
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Default Solvent/freeemup stuff

Try Hoppes #9 gun cleaner /solvent I have seen this stuff free up engines that could'n't be turned any way including hammer & drift on the piston top.
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Old 08-26-2003, 06:07 PM
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One way to clean an engine is to slow-cook in antifreeze. Just don't use the cooker for anything else ever again, and be careful with the antrifreeze of course. It removes all kinds of built up gunk and frees up stuck engines quite well.
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Old 08-26-2003, 09:45 PM
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Wow... lotsa good stuff

Well, I Got two of my engines started and now i feel that much closer to being a real hobbyist.

The .60 i have in the trainer (brand unknown ... there is two bars with what looks like a sideways V between them) started up right away but doesn't like to run at idle w/o the Glo Plug heater. I used the fuel that came w/ all my stuff and i imagine it's pretty old so i hope that is why.

My Fox 78 runs great (kinda same thing happening with idle, Runs for a few minutes w/o heater then slowly starts to die out... seems like it's flooding) and started up on First spin after taking it all apart and cleaning it.

It was soooo cool to have them running... suckers are LOUD and man does the 78 spin fast. I couldn't even keep it on full throttle for fear i'd go deaf!

Thanks for all the info guys!
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Old 08-27-2003, 02:25 PM
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About the .60, i think you need to replace the glow plug. try an os #8 or a3 plug. the a3 is hotter, so try the #8 first. the only reason i reccomend the os plugs is they last forever. about that .78, it shouldn't really go above 12,000 rpm. two strokes can over rev, and it will ruin them. try putting on a bigger prop to absorb the energy
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Old 08-28-2003, 12:35 AM
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Default Castor Oil

If you expect that Fox engine to last very long you better think about running Castor Oil in your fuel. Fox engines are designed to be used with at least some Castor.
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Old 08-28-2003, 12:01 PM
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I have no idea what kinda fuel i'm running as it came with the whole sh'bang. I'm guessing it's a couple years old and even though it was more or less sealed i bet it's lost some of its "pow"

So i ordered a case of 10% from tower along with new glow plugs. I got #8's and also some of Fox's r/c longs (what's the difference between long and short exactly?) Also ordered a bunch of other goodies Should be here in a few days so i'm gonna wait before firing up those engines again.

WHY CAN"T I JUST FLY NOW!!!!! mwhaaaaa
(Patience aint a virtue it's a pain in my butt!)
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