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Oct 05, 2005, 09:18 PM
Thread OP

please comment on OS FL-70

Hi there !

Calling on folks who purchased this engine ;

The specs look nice , as the magazine reviews .

Still i would like to ear your comments on this engine .

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Oct 05, 2005, 09:27 PM
In Massive Debt
Cheaper version of the OS 70 surpass...

Single needle adjustment, instead of dual.....Plastic backplate...ect...

Its not a very high performance engine, and it probably wont last too long, and you would be better off going with an engine like the magnum 70 or the OS 70 Surpass II...
Oct 06, 2005, 08:27 AM
ProBro #1889
DsWright's Avatar
avoid the FL 70 like the plague......

Go with the surpass or a magnum
Oct 06, 2005, 08:52 AM
3 cylinders or more...
Radial power's Avatar
aviador, with the FL-70 OS engines is only trying to create a low cost four stroke engine that peoples will buy thinking "hey, it's an OS, it can't be bad".
If you are looking for a cheap four stroke there are other choices (Magnum comes to mind... ); if you are looking for a reliable engine from OS, have a look at there:

Tower hobbies

With just 30$ more you can get the FS-70 II surpass.

Finally, I just remembered of this thread that ended talking about the FL-70:

Ringed or not ringed

Hope this helps .
Last edited by Radial power; Oct 06, 2005 at 08:54 AM. Reason: Modified second link
Oct 06, 2005, 02:02 PM
S.A.D. member
ivanc's Avatar
Has anyone had the FL-70? I'm interested in the comments of someone who actually owned and ran one.

I never had one so I'll comment on what I read about it:

Ringless ABN (or ABL?) piston/sleeve: I don't see anything wrong with it - this technology is used by OS for years in their 2-strokes and it's proved successful. As far as I can understand from the owners who had it happen, the nickel liner peeling is caused by runnin the engine lean. I had an OS 46FX which I purchased used (and abused) and I never had a problem with it. The ringless ABx technology is a proven design in 2-strokes. I don't see why it shouldn't be used in 4-strokes.

Airbleed carb: There are other 2- and 4-stroke engines with airbleed carbs and they have reliable idle and throttle response with no hesitation - I own one - a TH 40ABC which is an (almost) exact copy of the OS 40FP and it idles and throttles up as good as my 2 needle valve carb engines. The main drawback is that the idle is a little higher than compared to a 2-valve carb.

Carb location: Unlike the FS-70SII and it's Magnum clone XL-70RFS, the carb is offset from the centerline of the engine and cannot be rotated. I wouldn't consider this as a drawback as most 4-stroke engines do not offer carb rotation either and their carbs are offset too. I'd consider the FS-70SII and Magnum XL-70RFS more flexible and easy to adapt, compared to other 4-strokes, so IMO this is not a drawback for the FL-70.

Plastic backplate: I don't see anything wrong with it. It reduces engine weight. It doesn't hold anything (except a nipple for silicone tubing to the muffler), so I don't see a reason for it to break.

Engine break-in: As it's an ABN engine, the break-in process is simpler and shorter compared to a ringed engine - this is an obvious advantage of the FL-70.

Price: Although priced lower than the FS-70SII, its price is still higher than the Magnum XL-70RFS, so IMO the Magnum is a better buy as being fully equivalent to the FS-70SII.

Again, my comments are NOT based on my personal experience with this engine. For the reason stated above (price) I do not consider purchasing the FL-70 (as well as any OS LA engines for the same reason) in the near future, so I might not have any personal experience with it anyway.

Oct 10, 2005, 12:22 PM
Registered User
I have installed an FL70 in a Super Chipmunk, and although the model was designed for 60 size 4s the FL70 provides better power for similar weight. In the early days it was a little tight, but this is not un-usual in a new abc. It has flown many flights and has had at least 2 gallons of fuel through it to date. It is totally reliable, easy to set up and ticks over as you would expect from an OS. Fuel is ProSynth 2000 a 10% nitro mix and fully synthetic.
From experience cannot really fault it, was offered it originally by the local OS rep to test and I have decided to keep the engine until his memory is restored.
Here's the Chipmunk.
Apr 25, 2009, 04:22 AM
Only the Cat knows why
baldmonkey's Avatar
Good for you! I love OS and even the cheap FL70 impresses me. I am on my second one now. But I have lost count of how many times I have bought and been dissapointed with SC etc
Apr 25, 2009, 04:26 AM
I too bought an FL-70 and am very pleased with it. Don't know why so many people diss this engine...
Jan 18, 2010, 12:33 PM
Registered User


this engine is awesomw set it and forget it no problems will not run upside down thou otherwise 5 gallons thru it now still like new
Jan 18, 2010, 05:05 PM
Registered User
Hmmmm. Nine posts in 5 years.

Not nearly as exciting as the O.S. 46AX thread.
Jan 19, 2010, 04:37 AM
Registered User
My instructer runs one in his Airsail DHC1 Chipmunk. He runs it inverted. Has no issues.

I purchased one from our club treasurer to put in my Tony Nijhius Hawker Hurricane. Initially I was trepidatious about running it inverted due to the Airbleed Carb, but TT four strokes run Airbleeds as well and they seem to run fine upside down.


Jan 31, 2010, 10:55 AM
Registered User
no problems with mine. perfect for a cub.
Jan 31, 2010, 05:13 PM
The people that bad mouth them are the ones that never owned one. Pretty my the same on the 46AX thread. The ones that like them, own them.
Jan 15, 2015, 04:12 PM
Youtube channel : solentlifeuk
solentlife's Avatar
Originally Posted by glowguy47
The people that bad mouth them are the ones that never owned one. Pretty my the same on the 46AX thread. The ones that like them, own them.
OLD THREAD I KNOW >>> but had to post !

Sorry to dissapoint you but I have FL70 in my Extra and it is the most useless piece of crap I have ever had ... its just totally gutless.

The Extra should do verticals and good aerobatics on a 70 ... but this just fails to pull the skin of a pudding let alone haul my Extra. I've been running Glow for over 45 yrs and I can tune an engine ...

My honest opinion ... spend a little more on the Surpass or get a Magnum or similar ... anything but this POS !!

OS - what were you thinking of ? We want budget priced - but not crap performance !

Jan 21, 2020, 03:31 AM
Registered User
Monza Red's Avatar
Mine's alright in my BE2.

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