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This thread is privately moderated by pacoflyer, who may elect to delete unwanted replies.
Oct 25, 2013, 09:53 AM
Trader Rating: 5
Registered User
For Sale

OS 120 Gemini Twin


Almost new OS 120 Gemini twin.
Bench run once just to hear her purr.

$375 shipped.
Thanks
Last edited by pacoflyer; Oct 28, 2013 at 06:22 AM.
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Oct 25, 2013, 07:54 PM
Trader Rating: 123
Flying RC since 1962
sdstick's Avatar
Are parts still available for this engine?
Oct 25, 2013, 08:20 PM
Trader Rating: 133
UAS Pilot - FAA# *******HRK
CryHavoc's Avatar
Quote:
Originally Posted by sdstick
Are parts still available for this engine?
Only those shared with the 160 Gemini twin.
Oct 26, 2013, 02:28 AM
Trader Rating: 1
Registered User
Which is pretty much only the connecting rod.
All other parts are either discontinued or parts you probably wont need to change like (rocker cover)
Oct 26, 2013, 12:13 PM
Trader Rating: 123
Flying RC since 1962
sdstick's Avatar
I am getting ready to build a Sig 1/4 scale Cub, this would be a nice engine for it but not being able to get parts sure scares me.
Oct 26, 2013, 12:47 PM
Trader Rating: 123
Flying RC since 1962
sdstick's Avatar
What is the weight and power difference between the 120 twin and 160 twin?
Oct 27, 2013, 09:38 AM
Trader Rating: 195
Go fast, pull up.
Fidelity101's Avatar
I've seen this engine in person and it's beautiful! Pacoflyer is a top notch seller...he's new to rcgroups but has been very active in rcuniverse for many years under the same username. Buy with confidence!

Specs for 160:
SPECS: Construction: Aluminum and Aluminum alloys
Displacement: 13.26cc (x2) or .809 cu in (x2)
Bore: 27.7mm (1.09")
Stroke: 22.0mm (.866")
Power Output: 2.0 BHP at 10,000 RPM
Weight: 1100g (38.8oz)
Practical RPM Range: 2,000 - 10,000 RPM
Length: 120mm (4.72") from backplate to front of the drive washer
Width: 196mm (7.72")
Height: 80mm (3.15")
Crankshaft Thread Size: 5/16-24
Suggested Props: 15x8, 16x6, 18x6, 18x7, 18x8, 20x6


Width (outer cylinder jacket to outer cylinder jacket): 120mm (4.72")


Specs for 120 series 2:
From the tech notes:

SPECS: Construction: Aluminum and Aluminum alloys
Displacement: 9.95 cc (X2) or .607 cu in (X2)
Bore: 24.0mm (.945") Stroke: 22.0 (.866")
Power Output: 1.7 BHP at 10,000 RPM Weight: 1090g (38.5 ozs)
Practical RPM Range: 2,000 - 10,000 RPM
Crankshaft Thread Size: 5/16-24

Length: 120mm (4.72") from backplate to front of the drive washer
Width: 196mm (7.72")
Height: 80mm (3.15")
Suggested Props: 14X9,14X10,14X11,15X8,15X9,15X10,16X6,17X6,18X6
Last edited by Fidelity101; Oct 27, 2013 at 09:50 AM.
Oct 27, 2013, 09:44 AM
Trader Rating: 195
Go fast, pull up.
Fidelity101's Avatar
Just found this...regarding replacement parts:

Quote:
Originally Posted by corsair167
My information comes from a 1990 2nd edition OS Engines exploded views book. Listed by part numbers, the Gemini II is the better engine and shares alot of parts with the 160. Rods are used in 120II,160,240, & 320. Cylinders are different, but heads, crank, case, cam,etc are the same as the 160 twin. I have a 160 Gemini purchased new in the 90's. I use Wildcat 2-4 stroke fuel at 10% but my Satio 150 likes 15%. Hope this helps. If you want, I can email the info too. Larry
Oct 27, 2013, 09:55 AM
Trader Rating: 195
Go fast, pull up.
Fidelity101's Avatar
Quote:
Originally Posted by Vigger
Which is pretty much only the connecting rod.
All other parts are either discontinued or parts you probably wont need to change like (rocker cover)
Vigger, I'm not sure this is accurate information...according to the OS users manual as well as rcuniverse and rcgroups posting from the past several years. It would be an accurate statement if you were talking about version 1, but this is clearly version 2 which shares many of the same parts as the 160.
Oct 27, 2013, 02:36 PM
Trader Rating: 1
Registered User
Quote:
Originally Posted by Fidelity101
Vigger, I'm not sure this is accurate information...according to the OS users manual as well as rcuniverse and rcgroups posting from the past several years. It would be an accurate statement if you were talking about version 1, but this is clearly version 2 which shares many of the same parts as the 160.
The first version is a completely different design based primarily on FS 60 with almost no parts shared with the later FT 120 (piston ring is one of the few)

The later version along with the FT 160 (sister models) is based of the FS 80 and the early pre-surpass models and thus shares a few parts. But those parts you would really be interested in (piston ring, piston, cylinder head, valves, and liner) is different.
However they do share the connecting rod, crank and cam but those parts might not be the parts you would need to change in a rebuild.

The heads are definitely not interchangeable, the bore is larger on the 160 and thus can not fit in the 120 head same goes for the valves.

I have all those engines, i can check and or scan the manuals if needed :-)
Oct 27, 2013, 03:29 PM
Trader Rating: 1
Registered User
And to make things even more complicated, 3 very different con rods with same part number has been used in this engine since it's introduction. And since this is one of the earliest it is hard guess which of those this engine has.

Parts or not, this engine is very nice if you don't care too much about the power/weight ratio i will definitely recommend this engine.

@Seller: If you haven't sold this engine by the end of the month, i'll take it for a bit lower price if interested :-)
Oct 27, 2013, 03:50 PM
Trader Rating: 195
Go fast, pull up.
Fidelity101's Avatar
Ok, you've got more experience than I... Thanks for the good information!
Oct 27, 2013, 09:24 PM
Trader Rating: 236
Registered User
This is a great deal on this engine and should run great for many years. I have NEW pistons, rings, heads, cylinders, and valve covers for this engine if anyone decides to buy this engine. I also have a nice used crankcase. this engine should be priced over $500.... can't believe it's still here.....
P.S. Pacoflyer is a fantastic person to deal with, don't let the zero feedback scare you, a true gentleman and you will get exactly what's advertised
Last edited by shooboy; Oct 27, 2013 at 09:30 PM.
Oct 27, 2013, 09:38 PM
Trader Rating: 195
What - Me Hurry?
redball8's Avatar
There's a fellow on RCU that offered full price for the motor, and the RCU listing was taken down (technical problems with the site, too). My guess is it's sold.
Oct 27, 2013, 09:43 PM
Trader Rating: 236
Registered User
It may be, I spoke with him yesterday personally at a swap meet and I thought he said he still had it. Of course it may have sold in the last 24 hours. I was thinking of selling my 160 and that's what brought up that conversation....Shoo

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