Need info on old OS 120 four stroke
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RE: Need info on old OS 120 four stroke
http://manuals.hobbico.com/osm/fs-120s-e-manual.pdf
look at this manual for some guidance i now the manual is not showing the double valve covers but the parts list is the same. hope it helps
Ron G.
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RE: Need info on old OS 120 four stroke
the pushrods and lifters are the same as the later surpass 1.20 engs. my eng. turns a 15X8 Master airscrew K series prop at 8500 rpm on the ground. i use 10% nitro and all caster Power
Master fuel. your short push rod has lost its temper and is wearing on the ends. pn #45566000 is the # for the pushrods. the same pushrods fit the FS 120S, SII,
sIII, SE, FT 120II and the FF 240 & 320 engs. i bought my spairs from Tower.
Master fuel. your short push rod has lost its temper and is wearing on the ends. pn #45566000 is the # for the pushrods. the same pushrods fit the FS 120S, SII,
sIII, SE, FT 120II and the FF 240 & 320 engs. i bought my spairs from Tower.
#28
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RE: Need info on old OS 120 four stroke
ORIGINAL: TFF
Not a powerhouse, but no 4 strokes in the early 80s were. Dont lug it too much and dont make it scream. Good for sedate airplanes like Cubs or a big Telemaster. Not a 3D or race engine.
Not a powerhouse, but no 4 strokes in the early 80s were. Dont lug it too much and dont make it scream. Good for sedate airplanes like Cubs or a big Telemaster. Not a 3D or race engine.
Yes, OS's earliest effort at producing a 1.20 sized pattern four-stroke does indeed have a few limitations. But it IS a good engine. I wish I still had my first four-stroke, the OS FS-120.
Ed Cregger
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RE: Need info on old OS 120 four stroke
ORIGINAL: ScottMcM
I have been tinkering off and on with this engine, and still can't get any decent rpm's out of it. With a 15x6 apc propeller, omega 15%, I get 7000rpm, with 10% omega, I get 6500rpm, and with 30%, I get 6800rpm. It will idle down to around 2000rpm with the 15 or 30%, but it doesn't idle well with the 10%. There is a huge amount of ''slobber'' coming out of the crankcase nipple. I have checked and reset the valves, checked and reset the timing, new glowplug....any ideas, or am I expecting too much from this old warhorse? It idles and transitions great, and runs smoothly throughout the rpm range. I was a little surprised at the drop in rpm's using the 30% fuel. I expected it with the 10%, but not the 30%.
I have been tinkering off and on with this engine, and still can't get any decent rpm's out of it. With a 15x6 apc propeller, omega 15%, I get 7000rpm, with 10% omega, I get 6500rpm, and with 30%, I get 6800rpm. It will idle down to around 2000rpm with the 15 or 30%, but it doesn't idle well with the 10%. There is a huge amount of ''slobber'' coming out of the crankcase nipple. I have checked and reset the valves, checked and reset the timing, new glowplug....any ideas, or am I expecting too much from this old warhorse? It idles and transitions great, and runs smoothly throughout the rpm range. I was a little surprised at the drop in rpm's using the 30% fuel. I expected it with the 10%, but not the 30%.
If you are getting excessive slobber out of the crankcase vent nipple, the idle is crappy, chances are your engine's compression is down (bad ring). I would replace the piston ring and break it in again. Just run it a bit rich with the new piston ring and don't let it get very hot for a while. All of this can be done in the air.
The only glow plug that I would use in this engine are the OS Type F. Get a new one and install it AFTER break-in. Don't worry about the idle and transition to full throttle until after the ring has seated. Then install the new glow plug and be patient. Unlike some two-strokes, making very large changes in the needle settings on this engine can lead you to missing the "sweet spot" that you are searching for. Four-stroke model engines are a different experience from the two-strokes. Good luck. You have a great engine.
Ed Cregger
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RE: Need info on old OS 120 four stroke
I imagine parts are hard to come by for this old horse. Does anyone have a link to where I might purchase a ring? Again, thanks for all your help, guys. I am confident that I will eventually get it running right, and, more importantly, learn something along the way.
#32
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RE: Need info on old OS 120 four stroke
Frank Bowman makes very good piston rings:
[email protected]
Frank C. Bowman
1211 N Allen Ave.
Farmington, NM 87401
505 327 0696
Bruce
[email protected]
Frank C. Bowman
1211 N Allen Ave.
Farmington, NM 87401
505 327 0696
Bruce