Reassembly procedure. OS Gemini 120 & 160
 

I own an OS Gemini 120, and Gemini 160. I did not get the tool kit, nor instruction manuals with either of these motors. I will be needing the specifics of disassembly and reassembly and valve adjustment. Are there any application specific tools required for this task? I managed to find the users manuals on the OS web site, but I was unable to locate the specifics that deal with reassembly, which include the very critical reassembly procedure to assure proper valve timing, valve seting, etc. Thanks for your help.

RE: Reassembly procedure. OS Gemini 120 & 160
 

There really aren't instructions for assembly and disassembly of O.S. engines. They're all pretty simple, and there isn't any critical reassembly procedure.
The instruction manual for the engine should give the procedure for setting the valve clearances. Basically, though, you rotate the engine so one rocker arm/pushrod assembly is off the cam and set it. Rotate the engine and set the other. You use 0.04 mm and 0.10 mm feelers. The thin one fits and the thick one doesn't. O.S. makes a small valve-setting tool kit, available through your local hobby retailer:

OSMG6334 72200060 GAUGES TOOLS 4-STROKE $10.99

Setting the timing is also very easy. The crankshaft and camshaft gears have small marks. The camshaft gear (the big one) will have a small hole in it, and the crankshaft gear will have a dot. You just insert them so that the dot and hole are in the center and line up with the centers of the cam and crankshaft. They'll all be in a straight line with the timing marks in the middle.

Hope this helps out.

RE: Reassembly procedure. OS Gemini 120 & 160
 

bax, I just got a used good conditions gemini 160 with the old carburator style , the one with air bleed adjustment for idle, can you tell me wich is the best start seting for this screw?

and I want to know if you recomend me if I better buy the new style carb to put it, the one with two needle valvs?

RE: Reassembly procedure. OS Gemini 120 & 160
 

You set the air-bleed screw so that it blocks the hole 1/2-way as the initial setting. When you adjust the idle mixture, you turn it out to lean and in to richen. You do not need the two-needle carb.

RE: Reassembly procedure. OS Gemini 120 & 160
 

I have an old os ft 120 that runs great but has a bearing whin at low speed. Does anyon know where to get the bearings and how many. If I knew the size I could order from other sourses. Hobby Center seem they do not want to work on it. I need Help!!! LOVE this engine.
Mike

RE: Reassembly procedure. OS Gemini 120 & 160
 

All of the bearings are still available.

OSMG3060 26731002 FRONT BEARING 40-240 US$19.99
OSMG3076 22130004 MID BEARING 120-240 US$20.99
OSMG3040 22631019 FRONT BEARING 12-300 US$17.99
OSMG3120 46030008 REAR BEARING 108-160 US$24.99
OSMG3216 46031005 CAMSFT BRNG F 120-300 US$17.99

You'll need one of each, but two of the camshaft bearings (the last item in the list).

These parts can be ordered through any hobby retailer who sells Great Planes kits and accessories.