Honda Rancher TRX350 Top End Rebuild Part 4: Head Installation

Welcome to the fourth and final part of our Honda TRX350 top end rebuild series, in which we reinstall the head and its components onto our Honda ATV

Watch the video above and follow the steps below to learn how to do the head reinstallation portion of the Honda TRX350 top end rebuild. Use our Honda TRX350 parts diagrams for additional reference.

Honda Rancher TRX350 engine rebuild top end

Tools and Parts Needed - Honda Rancher 350 Top End Rebuild Head Installation


  • Ratchet and extensions
  • 8mm-14mm sockets
  • Spark plug socket
  • 6mm Allen
  • 10mm, 12mm, 14mm wrenches 
  • Screwdrivers
  • Torque wrench

Honda TRX 350 Cylinder Head Reinstallation

Step 1. Reinstall the dowels pins onto the front left and rear right cylinder head mounting bolts, then install a new cylinder head gasket with the tab facing toward the back of the engine.

Honda Rancher 350 top end rebuild cylinder head install

Step 2. Reinstall the cylinder head over its mounting bolts, then reinstall the dowel pins onto the right-side cylinder head mounting bolts.

Step 3. Reinstall the pushrods and the rocker arm holder. Torque the four retaining nuts to 28 foot-pounds in the sequence shown in the image below, then torque the central nut to 22 foot-pounds and the rocker arm retaining bolt to 5 foot-pounds.

Honda Rancher 350 top end rebuild

Step 4. Reinstall the two cylinder head bolts on the outer right side of the head and torque them to 5 foot-pounds.

Step 5. Install a new head cover gasket and a new O-ring into the rocker arm holder.

Honda TRX350 top end rebuild head gasket

Step 6. Reinstall the cylinder head cover and tighten down the bolts. 

NOTE: Don’t overtighten the bolts because they’re aluminum and can easily be stripped.

Step 7. Install a new spark plug and torque it to 13 foot-pounds.

Honda Rancher 350 engine rebuild spark plug

Honda TRX 350 Top End Rebuild Exhaust Reinstall

Step 8. Reinstall the motor mount upper bracket and reattach the cylinder to the bracket.

Step 9. Reinstall the air intake boot with the notch facing to the left side when looking at the ATV from front to rear.

Honda TRX350 Rancher top end rebuild

Step 10. Install a new exhaust pipe gasket, then reinstall the exhaust pipe and hand-tighten the exhaust flange bolts so the exhaust can still be maneuvered. Reinstall the muffler, then tighten its mounting bolts and the exhaust flange bolts.

Honda TRX350 engine rebuild exhaust reinstall

Honda TRX 350 Top End Rebuild Carburetor Reinstall

Step 11. Reattach the throttle cable to the carburetor, making sure there’s a little bit of play in the cable. Next, tighten the cable’s pinch bolt to lock it, then pull the rubber boot back over the pinch bolt.

Honda Rancher 350 engine rebuild throttle cable

Step 12. Reinstall the carburetor body cover, then reattach the choke cable to the carburetor, reinstall the carburetor assembly to the engine intake and tighten the intake clamp.

Honda Rancher TRX350 top end rebuild carburetor install

Step 13. Reconnect the float bowl heater’s electrical connector.

Honda Rancher 350 carburetor reinstall

Honda TRX 350 Top End Rebuild Fuel Tank Reinstallation

Step 14. Reinstall the fuel tank heat protector cover onto the frame.

Honda Rancher 350 top end rebuild fuel tank reinstall

Step 15. Reinstall the fuel tank on top of the cover and tighten the three 10mm mounting bolts.

Step 16. Reconnect the fuel line from the tank to the carburetor assembly.

Step 17. Reinstall the air intake tube across the rear of the fuel tank and hold it in place with the plastic mounting rivet. Reroute the vent hose up through the aperture in the intake tube.

Honda Rancher TRX350 engine rebuild fuel tank tube

Step 18. Reinstall the petcock valve extension and turn it on.

Honda TRX 350 Top End Rebuild Airbox Reinstall

Step 19. Slide the airbox assembly back into position behind the carburetor, then reattach the air intake tube and the carburetor intake boot. Tighten the clamps on the intake tube and carburetor intake boot.

Honda Rancher 350 top end rebuild carburetor intake boot

Step 20. Reconnect the airbox vent hose and reinstall the mounting bolt beneath the airbox assembly.

Honda TRX 350 Top End Rebuild Final Steps

Step 21. Reinstall the TDC inspection plug into the right side of the crankcase.

Honda Rancher 350 engine rebuild TDC inspection plug

Step 22. Reinstall and reconnect the battery, then reinstall the body panels and the seat and you’re done.

Go easy on the Rancher 350 for the first few miles after the top end rebuild to avoid maximum throttle and aggressive acceleration. Be progressive with the throttle so the new internal parts will bed in nicely. 



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