Notices
O.S. Engines Support Ask Bill Baxter your questions about O.S. Engines.

os fs 52s

Old 04-25-2007, 07:02 PM
  #1  
Junior Member
Thread Starter
 
Join Date: Dec 2003
Location: chatsworth, GA
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
Default os fs 52s

I have an os fs 52 surpass. The problem I'm having is with idle. If I adjust the idle for smooth operation it dies when I gas it. The only way I can get a smooth transition from idle to full throttle is to run the idle rich. However, when I adjust it that way it vibrates terribly like it's got the "Hippy Hippy shakes". I am using 15% Cool Power and 12-4 prop. I have also tried an 11-7 prop just for the fun of it, it made no difference. The Spray bar of the carb is located abt 3/4 the way up from the bottom of the fuel tank. Any suggestions ?
Old 04-25-2007, 09:58 PM
  #2  
Senior Member
 
Join Date: Feb 2006
Location: Arroyo Grande, CA
Posts: 4,465
Likes: 0
Received 2 Likes on 2 Posts
Default RE: os fs 52s

I've got two of those engines and they are without a doubt the best engines I've ever owned. I'm guessing that your problem is just mixture settings. Try this setup and see how it works for you

First, you will need a tach to really tune the four strokes. Your ear just isn't going to be able to detect the top end like you can on a two stroke.

Get the engine running, the 12x4 prop is a good load, and let it warm up for a minute or so. Now go full throttle and very slowly lean out the top end for maximum RPM. It takes a bit for the four stroke to catch up with the mixture change, so count to 10 between each click of adjustment. Once you have found maximum, it should be around 11,000 rpm, depending on how well broken and prop, richen it up so it drops around 500 to 600 RPM from peak.

Now cut back to as slow as the engine will run with out stalling, what ever speed this is. lean out the idle for maximum speed. If it starts faltering as soon as you start to lean it out, richen it up to maximum speed then go 1/4 turn futher rich. Cut the throttle back again to full idle, and you should keep running at aproximatly 2000 rpm. Note that your carb will not be fully closed at this point.

Now re-adjust the high end again. Changing the idle when it is way off will affect the top end adjustment. Use the same 500 to 600 rpm drop from full

Back to idle, does it hold a reliable idle now?? If not, re adjust the idle. But this time, you are only going to turn the needle 1/16th turn at a time. Before you start, jam the throttle open. Does it die imedatly, or does it sputter and slowly gain RPM. If it dies right away, you are to lean on the idle, start by click (1/16th turn) at a time until you can jam the throttle and it barks to life. If it sputters, it is to rich. lean it by the same clicks. That engine will jump when you hit the throttle. When it is broken in, you can get it to bark like a gasser by quickly flicking up and down throttle.

Once you have it right, go back and adjust the high end once again, then give the low end it's final tweek to prefection. Once set, and the engine if broken in, you shouldn't need to touch the needles for a long while. I flew one of my 52's through two crashes, one breaking the mounting lug off the back plate, and after rebuilding the plane on the first and then building a new fuselage on the second, that engine fired up right away and required nothing more than throttle servo adjustments. Great engine.

Don

PS, If the engine has a gallon or more fuel through it, you may want to check the valve lash, but don't adjust them it unless they are way off.
Old 04-26-2007, 05:53 PM
  #3  
Junior Member
Thread Starter
 
Join Date: Dec 2003
Location: chatsworth, GA
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
Default RE: os fs 52s

Don
I made the adjustments per your instructions. Here are the results. Top end 12,000 RPM richened up to 11,500, Idle leaned out as far as I can and still acheive instant jump to wide open RPM is around 2,500. I still have a little shaking (not a smooth idle) but, it is a lot better than what I had. If I go any slower with the idle it shakes quite a bit and runs erractically. I think I will be happy with the way it is performing now. Do you have any further suggestions? I wonder if I should use a different prop such as a 12-6 to get the top end a little slower.
Thanks for your help.

Gary

Oh, by the way this engine probably has 1.5 to 2 gallons run through it.
Old 04-26-2007, 06:47 PM
  #4  
Senior Member
 
Join Date: Feb 2006
Location: Arroyo Grande, CA
Posts: 4,465
Likes: 0
Received 2 Likes on 2 Posts
Default RE: os fs 52s

Gary, you might try replacing the fuel lines. I was filling mine a couple weeks back and I saw what looked like a spider web floating in the engine compartment. When I stopped the pump, it went away. When I started the pump again, it came back. I had a pin hole in the line. This screws up the mix a bit. Also, you may smear some vasiline around the intake manifold to carb joint, along with around the needle valves. This will show up a bad/leaking Oring that needs replacing. Last, try a fresh OS Type F plug. One of the guys at the field used to be tech support for Novel and he said that some types of contamination will damage the glow plugs to the point of not providing low end reliability. Personaly, I've never seen a glow plug that was defective that glowed when the battery was applied. At least not that I could tell. I am not an expert here though.

I run the APC Sport 12 1/4 x 3 3/4 props and they work well. With the trainer, after two flights, they were usually 11 1/2 x 3 3/4 though. They pull well and you can run the idle a bit faster and not overpower on landing. You will not get as much top end, but if that is what you are after, you need a 2 stroke. I also ran 12x6 props for a while. I don't really think that a different prop will make a difference, not one that is in the power range of the motor.

Did you check the valve lash? It also may be causing a little roughness.

Oh yes, one more question, are you running the engine inverted? Idle there can be a problem and an onboard glow power may be needed.

One more question, how slow can you get it to idle without shaking, even with a slow response to high end.

Another idea just popped into mind. Turn in both needle valves to stop, don't force, and count the turns needed as accuratly as you can. Now remove them. Put an extention on the pressure line to the tank and blow into the tank. It shouldn't take much to get fuel blowing out of the high speed needle valve hole and out the carb mouth. A bit of contamination may be getting into the lines and needle valves causing an uneven supply of fuel. I run a fuel filter on both the pressure and supply lines. I've take a tank out of a plane after just a gallon of fuel and there will be a big black ring where the pressure line is pointing in the tank. Filtering out any crud that can get to the needle valve will only help.

Let me know how it goes.

Don

Old 05-01-2007, 06:53 AM
  #5  
Senior Member
 
meaden's Avatar
 
Join Date: Jan 2006
Location: Decatur, GA
Posts: 626
Likes: 0
Received 0 Likes on 0 Posts
Default RE: os fs 52s

Campgems,

Thanks for your post it helped me dial in my 52.

I thought I'd post my numbers for airadical.

With a MAS 12x6 K series on 15% fuel I got 10,500 (rich) on the top end and 2,500 on the idle.

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
Trackbacks are Off
Pingbacks are Off
Refbacks are On


Thread Tools
Search this Thread

Contact Us - Manage Preferences 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.