How to Rebuild a Traxxas 2.5 Engine

Wash the crankcase and bearings with denatured alcohol or electric motor spray. Blow compressed air inside to dry out the interior of the crankcase.

Assess the bearings and check that they spin freely. Check for any damage to the O-ring gasket inside the exhaust along with the back plate's O-ring gasket.

Drip a few drops of synthetic motor oil into the ball-bearings, then asses the crankshaft for any damage near the intake port. Twist the crank pin, and check that it can rotate smoothly without any lateral wiggle room.

Insert the crankshaft into the crank bearings, then assess the carburetor's O-rings and the rubber throttle arm for imperfections.

Loosen the high-speed needle, then slide it out. Cleanse the carburetor body and high-speed needle housing with denatured alcohol or electric motor spray.

Spray compressed air and dry the cleaned engine components. Tighten the high-speed needle into the needle housing all the way closed. Unscrew the high-speed needle four-turns out from fully closed to return it to factory-recommended settings. Install the carburetor in the crankcase, then tighten the pinch bolt

Drip a few drops of oil into the wrist pin bore on the piston before you install the wrist pin. Slide the connecting rod into the piston so that the piston's skirt relief lines up with the oiler hole. Align the wrist pin bore within the rod with the wrist pin bore inside the piston, then insert the wrist pin through the larger opening on the piston.

Clip the wrist pin clip (G clip) by fitting it into the groove on the wrist pin bore of the piston. Face the connecting rod's oiler toward the crankshaft, then install the piston and connecting rod through the top of the engine encasement. Drip a few drops of oil into the crank pin, then install the connecting rod onto the crank pin. Rotate the crank pin until it is positioned at the bottom-center of the crankcase.

Lubricate the piston, then insert the sleeve into the engine encasement, making sure to push it as far down into the engine case as possible. Check that the slot on the sleeve is connected with the pin located in the back of the engine case opening.

Insert the copper head-gasket through the sleeve. Press the cooling head down flush onto the sleeve, then thread the five head bolts incrementally in an 'X' shape; in other words, tighten one a quarter turn, then move to the next one diagonally across from the first. Repeat this process until all are tightened, this will ensure a proper seal. Attach the back-plate and starter shaft to the engine encasement.

Spin the starter shaft while you apply strong pressure toward the crankshaft. Key the starter shaft inside the crank pin, then connect the back plate and the engine case. Tighten their connection with the 4 screws, then screw in the glow plug.

Install the split-cone washer onto the pilot shaft so that the larger opening faces toward the engine case. Install the flywheel onto the pilot shaft, then connect it with the split-cone washer. Tighten the flywheel nut with 62.0 in-lbs of torque pressed against the flywheel.

Insert the clutch shoes into the flywheel, then match up the flywheel pins with the holes on each clutch shoe. Cleanse and lubricate the two clutch-bell bearings, then install ball bearings on each side of the clutch bell. Install the clutch bell onto the pilot shaft, then attach the 5.0 E-clip.

Cleanse the roller clutch using denatured alcohol, then lube it with a few drops of synthetic motor oil. Connect the EZ-Start system with the starter shaft, then tighten the engine case with three screws. Attach the exhaust header and pipe assembly back onto the backside of the engine case with two screws.