Sunday, 16 October 2011

Rebuilding a Traxxas TRX 3.3 Carb

I've not even ran my Revo 3.3 in anger yet and I'm doing stuff like this! But for the sake of helping others (and reminding myself) in future, i grabbed some pictures (sorry about the quality, my work lights are a bit powerful and focused!) and decided to make a bit of a tutorial.

This should also apply to other engines that use the same carb, such as the TRX 2.5

My main issue, if your not aware came from me having continued problems with the TRX 3.3 engine, where it was suffering major air leaks, and during the attempt to sort those leaks out, it would appear i managed to strip the threads from the idle screw port in the carb body. Rendering it useless.

So i obtained a new body, Traxxas Part Number - 5234


First of all you need to remove the engine from the chassis and then remove the carb from the engine block, buy releasing the small nut on the end of the pinch pin.


Remove the High Speed Needle using a deep 8mm socket, don't loose the two washers or the banjo fitting



Remove the two blanking plugs using Allen keys



Remove the Idle Needle with a flat blade screwdriver


Remove the Low Speed Needle with a flat screwdriver


Loosen the Allen screw and remove the throttle arm


Gently pull the Dust Boot away from the body, just gently pull at it with your finger nail, then pull it forwards and it should come away completely from the slide


Using a flat screwdriver, carefully pry the Return Spring away from the body


Pull the slide out completely and keep it safe, clean it and the boot with some PTFE spray if you desire


Now to reassemble the carb, substituting any old and damaged components with new ones.

Insert the slide into the body and then careful reattach the return spring into the grove, the part of the spring that offsets the last coil should rest in the slot

The large groove in the slide should be in line with the idle screw, the narrow groove in the slide should be visible through the intake of the carb

Don forget to replace the dust boot, just pull it over and make sure it clings to the larger groove in the body and the groove in the slide




Now for  trick of the trade, i picked this up from a member on YouTube called Squirrelod who does many very helpful presentations for all things to do with RC models, its well worth a look, CLICK HERE to see for yourself.

This involves using Team Associated Green Slime to help seal the threaded items in your carb. This stuff is primarily aimed at suspension o-rings, but does work wonders for this too!


Pure and simply, just add a thin layer to any of the needle threads as you install them


Next replace the idle screw, DONT BE TO HEAVY WITH IT! As I've already suffered that weakness, factory setting is flush to the body


Replace the High Speed Needle using the 8mm socket, again, don't be too heavy handed with it, get it finger tight and then apply about a quarter of a turn to tighten it up

Remove the needle, add some green slime then turn it all the way in, then back it out 4 turns to the factory default


Do the same for the Low Speed Needle, the factory setting is to be flush with the end of the slide

Finally add the o-ring (should be a new one if you have replaced the body) and add some silicone sealant if you desire to reinforce the seal

Add the throttle arm too, but keep the screw loose as you will need to adjust this as you reinstall the engine.


Finally, refit to the engine, insert the carb into the block, with the pinch pin in place, then secure with the nut


Reinstall the engine and connect all electrical and fuel lines, don't forget to check the mesh of the pinion and spur gear and test it out!

Hope this has been of some help.

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