T-Maxx Troubles...Need Help

[only-half-evil]

So I bought a used T-Maxx 2.5 about a month ago. The previous owner ran maybe 10 tanks thru it after break-in...which mustve been 10 gentle tanks cuz theres hardly a scratch on it...then let it sit for a year. When I got it, it wouldnt start...but I got it running after putting it all back to factory tuning, a fresh plug and fresh gas. It ran...but not quite right. Got most of the bugs worked out of it, ran 2 tanks thru it...and now its back to being a pain. First...it runs hot as hell even after short runs. Second...the idle is so jumpy, even after idling for a good bit. Third...its hell to start. It takes forever...and thats with priming it and throttling it. Once it starts...it runs for a bit, stalls...and takes 3 to 5 minutes to restart. After every run, the plug looks nasty...both inside and on top. I've tried everything I can think of...starting at factory and slowing working up to a full turn out and a full turn in. It just refuses to get a decent tune and hold it. Only way itll stay running now is running rich enough that the fumes burn your eyes. Would love to get this running right...and not just give up and buy a new engine for it. If I have to do that, I'm gonna go with the 3.3...since I can get a new one for only $110. But if I go with the 3.3, I dont know what else Ill have to upgrade to handle more power. People with way more experience and knowledge than me...lend me your brain and please let me know what you think. Thanks.

 

[Mn Monster]

have you taken apart the engine ? it sounds like your piston skirt might be damaged. i had the same problem with my 2.5, hard to prime, hard to keep running (bad compression ) i would get it started, it would run very hot and than die. (killing glow plugs) pull your head off, and take out the piston and sleeve and check for any damage. looks can be deceiving ! if he ran 10 tanks with a bad tune, and lean settings, your rig would still look new, but could have engine damage !

 

[only-half-evil]

To be honest...my Nitro experience isnt that far along yet, which is why I havent torn the engine apart yet. This is my first Nitro engine...I'm not familiar with the internals at all. But, hell...if I'm probably gonna end up trading it in anyway, lets go for it ad see what happens. What exactly am I looking for? (If you know of a site with images, please include a link for it) And how much does a rebuild kit run?

 

[Snook Man]

http://traxxas.com/support/TRX-Engine-Rebuild-Instructions-0

You should be looking for any rust, wear or breakage to all the internals.

To check the pinch; once the sleeve and piston are removed from the block, slide the piston (in the correct orientation) up through the bottom of the sleeve. If you can push the top of the piston (without excessive force) even with or past the top of the sleeve the piston and sleeve are worn out and need replaced. Ideally you will want the piston to stop a few mm from the top edge of the sleeve.

Check the bearings to see if they spin smooth with no gritty feel, check the fit of the connecting rod, wrist pin and piston for excessive play and the fit of the rod to the crank pin.

Often an engine that has sat for a period of time without any after run procedure done to it prior to storage will developed rust on the steel crankshaft and bearings.
Starting an engine with rusty internals can often lead to premature wear. Some of the surface rust breaks free and flows through the engine acting like sandpaper along the way.

Replacing the piston and sleeve cost approx $50.00, but take into account if a new connecting rod, bearings or crankshaft is needed it adds to the cost and IMO is not worth a rebuild.

 

[Mn Monster]

here is a video that will help you take it a part. it can seem intimidating at first, but when you take it apart you will see that it's not as hard as it looks

[ame="http://www.youtube.com/watch?v=FNfFhJ3iEL0"]How to disassemble a Nitro Engine!!! (TRX 2.5) - YouTube[/ame]

 

[only-half-evil]

Thank you, both. Couldnt have asked for better. I will try that today and post what I find.

 

[Phins Fan]

I would say a reseal is in order to help control your temp a little better as well. The carb neck, backplate and anywhere you may have air leaking into the block and causing a lean condition.