OS10LA Spitting Fuel out of carb - RC Groups
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Jun 15, 2009, 03:30 PM
Registered User

OS10LA Spitting Fuel out of carb

Help, please...

PROBLEM, please advise...

Brand new OS 10 LA... 7x4 prop w/ spinner... 1/2" Muffler extension...

Excessive oil from exhaust pipe (literally soaking garage floor and plane), and raw fuel splattering out of carbuerator, like where to air goes IN??? opposite of how it should flow it seems... if i throttle back a bit, it will not blow
fuel, only at wide open throttle... No or litte smoke...

I try to lean the engine to prevent both symptoms, but it seems to be runnnig too lean; like if i quick-pinch the fuel line it does not climb in RPMS, just starts to die...

im afraid to go too lean? how do I know? Possible spinner too large? i think its a 1.5"... Seems to run OK other than that, if not a bit sluggish...

never had an engine this small, i dont know what to expect...

The best way to tune the engine is by sight and sound. If it sounds good
and has a thick bluish smoke coming out of the exhaust it is fine. That
being said, it should not be leaking out of the carb like that. I would
check to make sure that the carb is not cracked.

Its new. No cracks. No smoke. I know it should not be splattering fuel, thats why i wrote them. They said to send it in, but theyr gonna charge me $15 + s/h if they dont find anything wrong...
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Jun 15, 2009, 03:41 PM
Dieselized User
gkamysz's Avatar
What kind of fuel are you using?

Jun 15, 2009, 04:05 PM
Registered User


Fuel? I dunno... I got it at the LHS...

I think its 15%nitro w/ 18% oil...

It's called 2stroke-4stroke i think...

Im at work, fuel is in the garage..
Jun 15, 2009, 05:35 PM
Dieselized User
gkamysz's Avatar
Have you broken the engine in already? If you are still breaking it in , say at least the first several tanks like the manual states, the engine might not want to lean out much yet. Only more run time will improve it's operating characteristics.

This might sound like a dumb question, but is the engine running the correct direction? Some engines will start and run backwards.

Jun 15, 2009, 06:34 PM
You made that out of trees?
Boomerang1's Avatar
It may be so rich you cannot see the smoke for all the spray coming out of the exhaust.

With the engine running wind the main needle in slowly until it runs lean & stops through fuel starvation, then open it 1/2 turn & try again.

Lean runs will damage an engine if allowed to continue for a long period, leaning it out until it stops while trying to tune it will do no harm at all. This is exactly what happens when it simply runs out of fuel. - John.
Jun 15, 2009, 07:00 PM
The reviewer
XJet's Avatar
Most 2-stroke model engines *will* spit a lot of oil out the muffler when running fuel with 18% oil.

I suspect that some of the problem you're seeing is due to your muffler extension. When you push the fine mist of exhaust oil through a pipe like that extension, it tends to condense into larger droplets which, instead of blowing away in the prop-wash, fall closer to the engine creating an oily mess.

I *HATE* those extensions with a vengence. They rob most engines of power and are must a nuisance.

It's also not uncommon for 2-stroke model engines to spit some fuel out of the carby, although this is generally more common at lower RPMs when the effect of the intake port remaining open after TDC is likely to produce reverse-flow in the carby.

Since the LA series are plain-bearing motors, you *must* use a fuel that contains a good percentage of castor oil (Omega for instance). The castor provides a much thicker oil-film on the crankshaft journal and that not only reduces wear but also provides a better seal to stop crankcase pressure and fuel escaping through the front of the engine. If you run on fuel containing only synthetic oil then you will significantly reduce the life of your engine and possibly compromise its performance.
Jun 15, 2009, 09:57 PM
Resident giant scale guru
my c210's Avatar
my brodak 049 is doing the same thing. I am running a 20% nitro 7% castor blend in it, and it is fully broken in, however when I get it to a slow idle, i feel a mist of fuel from the carb. spraying on my hand. whats upp?
Jun 15, 2009, 11:06 PM
Dieselized User
gkamysz's Avatar
Flow reversion is rather normal at part throttle for many engines. It's not so common at full throttle unless the engine is below design operating RPM. It's just part of a single cylinder engine's characteristics. A "velocity stack" can help improve the situation.

What kind of RPM are you getting?

Jun 16, 2009, 09:48 AM
Resident giant scale guru
my c210's Avatar
Brodak 049 RC (2 min 48 sec)

My video
Jul 20, 2009, 09:10 AM
Registered User


Plane flies great and Ive gotten used to the fuel spitting... I keep a jug of windex handy to towel off the wings after a few flights... thank you all.
Jul 20, 2009, 10:59 AM
Registered User
earlwb's Avatar
Yeah with our normal 18% to 20% oil mix fuels, you can expect a lot of residue coming out the exhaust pipe. They are messy little buggers. Spitting a little fuel out the carb is normal too. Plus the front bushing on the crankshaft tends to ooze out some oil as well. The muffler to engine attach point tends to ooze some oil as well.
it is all normal. Adjust the engine until it is running happily. You are OK.
it is why all the model airplane kits always say to use coatings that are "hot fuel proof".

Do not use the low oil content fuels with less than 18% oil in them. After you have more experience running and using engines you might consider the lower oil content fuels, but the fuels are a lot more risky.
Jul 20, 2009, 04:42 PM
Registered User
I have a Super Tigere .40 has been runnubg great, I have flown my Sky Raider Mach II enough taht I am almost ready to Solo.
I flew it Saturday and then Sunday it went crazy. Spittig fuel out the Carb. and a lot out exhaust. I do have an extension, i.e. exhaust deflect tube, should I remove it?
Why would it all of a sudden do this?
Everyone said,Get a new one, need new bearings and seals. I always hate that. They changed my Glow Plug and it was new.
Help me guys,why does this engine not like to start after it gets Hot?
I run 15% glow fuel
Last edited by supernovam2; Jul 20, 2009 at 04:59 PM.

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