Notices
Glow Engines Discuss RC glow engines

Need info on old OS 120 four stroke

Old 03-06-2012, 06:47 PM
  #26  
raptor001
Junior Member
My Feedback: (8)
 
Join Date: Mar 2011
Location: ocala, FL
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Default 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.

Old 03-09-2012, 10:25 PM
  #27  
george76471
Junior Member
 
Join Date: Nov 2006
Location: , TX
Posts: 1
Likes: 0
Received 0 Likes on 0 Posts
Default 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.
Old 03-10-2012, 01:44 AM
  #28  
NM2K
Senior Member
My Feedback: (14)
 
Join Date: Jan 2002
Location: Ringgold, GA
Posts: 11,488
Likes: 0
Received 2 Likes on 2 Posts
Default 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.


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
Old 03-10-2012, 02:01 AM
  #29  
NM2K
Senior Member
My Feedback: (14)
 
Join Date: Jan 2002
Location: Ringgold, GA
Posts: 11,488
Likes: 0
Received 2 Likes on 2 Posts
Default 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%.


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
Old 03-10-2012, 02:28 AM
  #30  
ScottMcM
Senior Member
Thread Starter
My Feedback: (66)
 
Join Date: Jan 2008
Location: Bennettsville, SC
Posts: 1,171
Likes: 0
Received 0 Likes on 0 Posts
Default 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.
Old 03-10-2012, 03:01 AM
  #31  
jaka
 
Join Date: Dec 2001
Location: Upplands Vasby, SWEDEN
Posts: 7,816
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Need info on old OS 120 four stroke

Hi!
Also check the cam-timing!
Old 03-10-2012, 11:54 AM
  #32  
landeck
Senior Member
My Feedback: (1)
 
Join Date: Nov 2007
Location: Sandy Springs, GA GA
Posts: 1,710
Likes: 0
Received 1 Like on 1 Post
Default 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
Old 03-10-2012, 04:11 PM
  #33  
ScottMcM
Senior Member
Thread Starter
My Feedback: (66)
 
Join Date: Jan 2008
Location: Bennettsville, SC
Posts: 1,171
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Need info on old OS 120 four stroke

Thanks, I will get in touch with him.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.