Go Back  R/C Tech Forums > General Forums > Nitro Off-Road
Engine problem - Wont stay running BELOW 1/2 throttle? >

Engine problem - Wont stay running BELOW 1/2 throttle?

Engine problem - Wont stay running BELOW 1/2 throttle?

Old 05-14-2013, 09:37 PM
  #1  
Tech Fanatic
Thread Starter
iTrader: (5)
 
ZiG-87's Avatar
 
Join Date: Jul 2009
Posts: 897
Trader Rating: 5 (100%+)
Default Engine problem - Wont stay running BELOW 1/2 throttle?

So I'm not a nitro expert but not completely green either. I recently bought a nitro SC8 with the AE .28 that had been broken in but not run much more than that.

On my first trip to the track it ran alright for about 1/2 a tank, but then suddenly something happened, it had no power and the sound changed. It sounded like it was bogging pretty bad and then just quit a few seconds later. Tried to restart it, and I can get it to fire if I give it about 1/2 throttle while cranking, but the second I let off the throttle it dies. And while it's running at 1/2 throttle it's revved up pretty good, have to keep the wheels off the ground and all that. It also doesn't seem to want to rev as high as normal, either.

I've taken it apart, nothing is obviously wrong, but same result when I put it back together. Even reset the carb to factory settings, no difference.

I've never seen this before, not too sure what to do. Any advice would be appreciated..
ZiG-87 is offline  
Old 05-14-2013, 10:44 PM
  #2  
Tech Regular
iTrader: (3)
 
Join Date: Apr 2012
Posts: 335
Trader Rating: 3 (100%+)
Default

Originally Posted by ZiG-87 View Post
So I'm not a nitro expert but not completely green either. I recently bought a nitro SC8 with the AE .28 that had been broken in but not run much more than that.

On my first trip to the track it ran alright for about 1/2 a tank, but then suddenly something happened, it had no power and the sound changed. It sounded like it was bogging pretty bad and then just quit a few seconds later. Tried to restart it, and I can get it to fire if I give it about 1/2 throttle while cranking, but the second I let off the throttle it dies. And while it's running at 1/2 throttle it's revved up pretty good, have to keep the wheels off the ground and all that. It also doesn't seem to want to rev as high as normal, either.

I've taken it apart, nothing is obviously wrong, but same result when I put it back together. Even reset the carb to factory settings, no difference.

I've never seen this before, not too sure what to do. Any advice would be appreciated..
Check the exhaust because it could be that the exhaust is clogged and not letting the engine breath or rev. Also check fuel, and glow plug and shims. If you can take a picture because I have one beside me but hasn't been run for 2-3 years.
george919 is offline  
Old 05-14-2013, 10:57 PM
  #3  
Tech Master
iTrader: (15)
 
JoePit's Avatar
 
Join Date: Mar 2012
Location: Phoenix, AZ
Posts: 1,278
Trader Rating: 15 (100%+)
Default

Sounds like the engine dropped its nuts. Lean it out a bit.
JoePit is offline  
Old 05-14-2013, 11:05 PM
  #4  
Tech Regular
iTrader: (3)
 
Join Date: Apr 2012
Posts: 335
Trader Rating: 3 (100%+)
Default

Originally Posted by JoePit View Post
Sounds like the engine dropped its nuts. Lean it out a bit.
+1 but I never had that problem when my .28 pro dropped its nuts but try it out.
george919 is offline  
Old 05-15-2013, 05:20 PM
  #5  
Tech Fanatic
Thread Starter
iTrader: (5)
 
ZiG-87's Avatar
 
Join Date: Jul 2009
Posts: 897
Trader Rating: 5 (100%+)
Default

Ah I don't think it's had nearly enough through it to drop its nuts yet, and in the past when that happens the thing still runs on factory carb settings. But I tried leaning it out a bit, and then a lot, and it would run maybe down to 1/3 throttle.

Fuel is brand new, as are/was/is the glow plugs I've tried. I have noticed though, that the oil coming out of the exhaust seems blacker than normal. I think the engine ate some dirt or dust at some point maybe. No scratches on the cylinder walls though.

When I put it back together I sealed the backplate with RTV as I had noticed some residue around there. I don't suppose that would affect anything, would it?
ZiG-87 is offline  
Old 05-15-2013, 06:26 PM
  #6  
Tech Master
iTrader: (15)
 
JoePit's Avatar
 
Join Date: Mar 2012
Location: Phoenix, AZ
Posts: 1,278
Trader Rating: 15 (100%+)
Default

How's the compression?
JoePit is offline  
Old 05-15-2013, 07:17 PM
  #7  
Tech Fanatic
Thread Starter
iTrader: (5)
 
ZiG-87's Avatar
 
Join Date: Jul 2009
Posts: 897
Trader Rating: 5 (100%+)
Default

Feels more or less normal with the head on. I've just killed the battery in the starter, while it charges I'm going to take the carb apart again...
ZiG-87 is offline  
Old 05-15-2013, 07:31 PM
  #8  
Tech Regular
iTrader: (3)
 
Join Date: Apr 2012
Posts: 335
Trader Rating: 3 (100%+)
Default

Look into the exhaust and see if their is any debris in it. Also take the crankshaft off and if you can see lots of scratches dirt has gone into our engine. Also check if you needles are clean and the carb is clean.
george919 is offline  
Old 05-15-2013, 07:44 PM
  #9  
Tech Fanatic
Thread Starter
iTrader: (5)
 
ZiG-87's Avatar
 
Join Date: Jul 2009
Posts: 897
Trader Rating: 5 (100%+)
Default

I don't have a clutch tool right now so wasn't able to check the crank beyond what I could see through the carb opening, but I think I may have made some progress.

I completely stripped the carb and sprayed it all down with nitro clean. Got the engine to fire and it will allllmost idle now. I'm thinking maybe there was a plug somewhere that caused it to cut off fuel when the throttle was closed (ie needle fully in).

Hopefully now it's just a matter of tuning it again. Gotta wait a bit for the smoke to clear from my garage though. :P Thanks guys, I'll keep you posted.
ZiG-87 is offline  
Old 05-15-2013, 09:00 PM
  #10  
Tech Master
iTrader: (21)
 
Rsickles's Avatar
 
Join Date: Aug 2010
Location: Southeast USA
Posts: 1,335
Trader Rating: 21 (100%+)
Default

Originally Posted by JoePit View Post
Sounds like the engine dropped its nuts.
There's only one way to tell what dropping its nuts looks like...

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
Rsickles is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
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 On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.