Engine problem - Wont stay running BELOW 1/2 throttle?
05-14-2013, 08:37 PM
#1
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..
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..
05-14-2013, 09:44 PM
#2
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..
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..
05-14-2013, 10:05 PM
#4
05-15-2013, 04:20 PM
#5
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?
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?
05-15-2013, 06:17 PM
#7
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...
05-15-2013, 06:31 PM
#8
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.
05-15-2013, 06:44 PM
#9
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.
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.
05-15-2013, 08:00 PM
#10
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