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Old Dec 21, 2011, 03:13 PM
Plasmajoe is offline
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OS GEMINI I vs. II


Can someone explain to me the difference between the two series. I have tried to figure it out, but have struck out!

Thanks, Gordon
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Old Dec 21, 2011, 04:03 PM
CryHavoc is online now
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Gordon, I think the pushrods were redesigned/strengthened and the crankshaft is different somehow, i.e. bigger journals, harder material or something like that.

If you haven't already seen this thread it has more info - https://www.rcgroups.com/forums/show....php?t=1360292

Mike
Last edited by CryHavoc; Dec 21, 2011 at 04:09 PM.
Old Dec 21, 2011, 04:44 PM
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The FT-120 Gemini was the first four-stroke twin OS produced. The FT-120 II (Gemini II) was a redesign based upon their experience with the FT-120 and FT-240 Super Gemini. That redesign brought us the FT-160 and FT-300. The FT-120 II thus shares many parts with the FT-160, whereas the FT-120 is a bit of an orphan like the FT-240.

Rap on the FT-120 was that the crank would snap in a crash or prop strike, but I have no first-hand experience of such. One certainly sees more Geminis than Gemini II's NIB.

I'll look for the MAN article and post it if I find it.
Old Dec 21, 2011, 04:44 PM
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Old Dec 21, 2011, 05:33 PM
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Couple of articles from 1985 shed some light. The engine review points out differences between the original FT-120 and FT-160. Note that the cylinders/heads from the FS61 and FS90 are the same as the FT-120II and FT-160, for example. The "Foreign News" comments about Japan are also a bit helpful ...
Old Dec 21, 2011, 07:30 PM
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One big difference is the carb. The II has a better carb. I own both engines and they perform about the same. Never had any problems with the original at all.. Bought it in 1981.
Old Dec 28, 2011, 07:06 PM
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Gemini Engine


I too have an OS 4 stroke book with all part numbers and pictorial descriptions. PM me if you choose or need too. Larry


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