Rubberman72

Replaced with new carb body and new Orings. New traxxas glow plug. New 20% fuel. Just sitting there idling and it will overheat reaching 300* plus. HSN is 5 turns out(or more). I tested fuel lines and tank for air leaks and its good. Any ideas?

crispyspa

Even the most perfectly tuned engines will overheat if just left to sit and idle. The head needs airflow over fins to cool the engine.

Aside from that, if you've done everything correctly and it still overheats, the engine is shot....but then again, I never really could tune a nitro engine. [:'(] Which is why I took the easy way out and went brushless. It was a better choice for me, given how many times I actually run in a year anymore. I just have to check on the batteries every once in a while....easy peasy.

mopartybob

low speed needle too lean, and as mentioned, they are not meant to sit and idle for too long,

1QwkSport2.5r

If an ABC engine is truly overheated, it will just quit running. The sleeve over-expands and piston seal is lost until cooled off.

Idle mix is definitely lean, and possibly an air leak somewhere.

Main needle only controls fuel mixture from 3/4-WOT generally. It will do nothing for a lean idle mix. Always set the main needle to peak power and back off rich a little. Then set your idle for crisp throttle response. This will give you a nice tune.

Oh, and a properly tuned engine should not overheat just idling unless its 120*F outside. None of my engines ever hit over 280*F just idling. They usually cool off a bit.

Rubberman72

Maybe i also need a new sleeve/piston cause its impossible to restart if it dies in the 260` and up

1QwkSport2.5r

That may very well be the case then. Turn the engine over by hand with the engine hot and note the compression. If its bad it should have hardly any compression at all hot.

JoeMaxx

In my past experience I have never seen this problem where they hit 300 deg at idle.

Most worn engines I have seen will run for about 5 minutes then just die from compression leaks after they hit about 260 degrees as you have stated.

Rebuilding the engine is almost as expensive as replacing a Traxxas engine. You can use the Traxxas trade up program and get a new TRX 3.3 for about the price it will cost to rebuild this older engine. You purchase the engine from traxxas and then you use the box they sent the new engine to you than send the old engine back to them for shipping costs.

If you LHSdoes it for yougenerally does not cost any shipping of the engine back to Traxxas or they may have a handling fee. Still cheaper then buying a new engine. I have used it in the past but is has beenyears ago. Still running my TRX 3.3 engine that I got in the trade up program back in 2006. I dealt directly with Traxxas on my upgrade from the original TRX 2.5 that was in my 2002 4910Traxxas TMaxx. I dropped the 3.3r engineinto my 2004 Revo and moved the TRX2.5r from my Revo into my 2002 Tmaxx. Still running both trucks these days.
http://www.traxxas.com/v2/powerup/

Rubberman72

Too bad traxxas doesn't allow u to trade in 2 engines. I still have the old Pro15 too.

JoeMaxx

Only if you are willing to buy 2 engines But you can use the Pro .15 to trade up to the TRX3.3 without any problems if you choose to keep the TRX2.5.

smokeymaronejpfxb8

The traxxas engine i had was the 2.5 4910 model it was very touchy on the LSN set it flush with the body it's screwed into, HSN i had set at around 2.5-3 turns out , read up on tuning engines , the pinch test  is a simple way to set the LSN allso the idle gap makes alot of diff. Most of overheating involves the LSN , but an idling nitro engine will overheat for sure. Run it around for a few mins then check temp. Allso is that 300f , sounds alittle out there.

mufflerbearing

I find the "factory" setting have the LSN too lean and the HSN too rich, perfect recipy for an overheating crappy running engine. I run my LSNs on the rich side and HSNs on the leaner side. Engine will run cool and have tons of power. You do loose a bit of low end but its worth it IMO.

JoeMaxx

When I set the LSN I use a pinch test to see how long the engine will run once I pinch the fuel lines.   I like to see it run for at least 3 to 4 seconds when adjusting this needle.  You have to have the idle set right before you adjust this setting. 

The idle screw while you can eyeball it with the credit card opening it really should be set with the wheels off the ground.  Idle it up until the wheels spin than back it off until it does not engage the clutch.   This is your idle speed.

Than run the engine for a bit and pinch the fuel line then count your Mississippi's for 3 to 5 seconds.   5 seconds is on the rich side for the LSN.  Once these are set then it is only the HSN you need to play with most of the time. 

Where I live the HSN requires daily tuning to keep the engine temps in check.   SInce I have many different engines the hot temp is different for them all before they run too lean.     

skyraider71

Check the tank lid o-ring. I had issues with my new 2.5R overleaning for no reason.
A new tank has it running like a champ.

vxlsteve

The lsn actually controls idle until about 1/4 throttle..if you running hot at idle one of two things and both were mentioned..first if engines is worn out it want go to 300 degrees it will shut off first..that leaves lsn..it has to be lean..if my engine has been ran hard for ten minutes and temps are up to around 250 degrees if I stop and wait 60 seconds it will start cooling..all the way down to 200 degrees ...also if hsn is set correctly wot passes will cool it off ..at wot its dumping loads of fuel in the engine and that cools it off..
I'm running a OS .21 on my revo and want never run.
anything else for all the reasons stated above...