Go Back  RCU Forums > RC Airplanes > Questions and Answers
OS 25 FX Running Hot >

OS 25 FX Running Hot

Notices
Questions and Answers If you have general RC questions or answers discuss it here.

OS 25 FX Running Hot

Old 06-07-2016, 08:13 PM
  #1  
Thread Starter
 
Champstarr's Avatar
 
Join Date: Aug 2014
Posts: 118
Likes: 0
Received 0 Likes on 0 Posts
Default OS 25 FX Running Hot

Hi everyone,

I have a new OS 25 FX engine. I have been trying to break it in but runs hot an eventually quits. The plane never breaks into four cycle operation no matter how much I try to rich'n it up. I took out the HS needle and it is all clean. It loosens and tightens with no problem. I replaced all of the fuel lines inside and outside of the tank and tested the new tubing and tank for leaks and found none. I also replaced all brass tubing and verified that fuel is not foaming. I haven't made any adjustments to the low end as the manual states that it is preset to an optimal setting.

This is for a combat plane and I have this exact same setup (fuel system/engine) on an identical combat plane and it runs fine. What else can I do? Please help.

Thanks,
Old 06-08-2016, 03:47 AM
  #2  
 
aspeed's Avatar
 
Join Date: Jul 2011
Location: Ruthven, ON, CANADA
Posts: 3,460
Likes: 0
Received 7 Likes on 7 Posts
Default

Is the muffler fitting blocked or small? It really should run rich enough, with no muffler even, if opened 6 or 7 turns. You can check by blowing through the supply line in the needle valve while opening the needle and closing it. Otherwise, I would guess an airleak in the carb base. I had one motor that was too tight on the crank to case that heated up and never richened up or idled. You could put your finger over the tailpipe to increase the pressure to temporarily richen it and maybe blow out a piece of dirt or whatever. It may have snuck in somewhere and missed the cleaning.
Old 06-08-2016, 12:43 PM
  #3  
Thread Starter
 
Champstarr's Avatar
 
Join Date: Aug 2014
Posts: 118
Likes: 0
Received 0 Likes on 0 Posts
Default

The muffler fitting is standard size. I have this same setup on two other combat planes and they have no problems. I did verify that the muffler fitting isn't blocked.

However I did make another observation. In the segment of tubing that runs between the HS needle valve and the carb there is a steady stream of bubbles. I took apart the entire HS needle assembly, cleaned it with rubbing alcohol and put some removable thread locker on it. I will fire it up here shortly.

Originally Posted by aspeed
Is the muffler fitting blocked or small? It really should run rich enough, with no muffler even, if opened 6 or 7 turns. You can check by blowing through the supply line in the needle valve while opening the needle and closing it. Otherwise, I would guess an airleak in the carb base. I had one motor that was too tight on the crank to case that heated up and never richened up or idled. You could put your finger over the tailpipe to increase the pressure to temporarily richen it and maybe blow out a piece of dirt or whatever. It may have snuck in somewhere and missed the cleaning.
Old 06-08-2016, 02:47 PM
  #4  
 
Hydro Junkie's Avatar
 
Join Date: Nov 2004
Location: Marysville, WA
Posts: 10,538
Received 130 Likes on 123 Posts
Default

There's your problem, it's running way too lean if you see bubbles. I'd replace the fuel line between the needle and carb as well as the o-ring in the needle.
Old 06-10-2016, 08:45 AM
  #5  
TFF
 
Join Date: Oct 2006
Location: Memphis, TN
Posts: 4,183
Likes: 0
Received 1 Like on 1 Post
Default

Check prop balance, but I would take the carb of the new engine and put it on the old and old airframe and see if the problem follows.
Old 06-10-2016, 07:08 PM
  #6  
 
Pylonracr's Avatar
 
Join Date: Apr 2011
Location: Reno, NV
Posts: 918
Likes: 0
Received 5 Likes on 5 Posts
Default

Toss the OS remote needle and buy a remote needle from Dub Jett. I have many OS FX series engines and have had trouble with the remote needle on many of them. I am to the point now that I do not even bother. Dub gets like 25 or 30 bucks for the most trouble free needle assembly there is, and it weighs less than the leaky OS setup.
Old 06-11-2016, 03:28 PM
  #7  
My Feedback: (404)
 
ronwc's Avatar
 
Join Date: Jan 2002
Location: LARGO, FL
Posts: 502
Likes: 0
Received 2 Likes on 1 Post
Default

It is probably just the nv "o" ring, no big deal to replace. I assume you're using something between a 8x6 to 9x6 prop. Also the factory settings on the carb mean very little other than just getting it started the first time, they both need to be fine tuned when up and running.
Old 06-21-2016, 11:30 AM
  #8  
Thread Starter
 
Champstarr's Avatar
 
Join Date: Aug 2014
Posts: 118
Likes: 0
Received 0 Likes on 0 Posts
Default

I tore the engine down. Tried everything I could think of an what was suggested here. Still same problem. Last week I boxed the engine up and sent it back to OS for service. Waiting on their findings.

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.