How to Set Honda TRX400EX Cam Timing 

If the timing chain on a Honda ATV slips a tooth or is incorrectly laid over the timing sprocket during an engine rebuild, you have to reset the cam timing. 

Watch the video above and follow the steps below to learn how to set the cam timing on a Honda TRX400EX. 

NOTE: To access the timing cam, you’re going to have to do a bit of disassembling first. 

Honda TRX400 cam timing how to set

Honda TRX400EX Disassembly

Step 1. Remove the seat, plastics, fuel tank, and the engine cover beneath the fuel tank.

Step 2. Remove the air intake, and the top motor mount bolt and the pair of spacers that secure the cylinder head cover.

Honda TRX 400 cam timing set

Step 3. Remove the cylinder head cover from the top of the motor to expose the timing cam and timing belt.

Honda TRX400EX cylinder head cover

Watch the video below to see how to disassemble a Honda TRX 400.

Honda TRX400EX Setting the Cam Timing

Step 4. Remove the crankshaft cover and the camshaft inspection cover, located on the left side of the crankcase in the flywheel cover.

Honda TRX400 crankcase

Step 5. Rotate the crankshaft counterclockwise until the T mark on the flywheel lines up with the mark on the inspection hole. The motor is now at top dead center or bottom dead center (TDC or BDC). It needs to be at TDC, so look at the camshaft lobes and if they’re facing down, the motor is at TDC, or at BDC if they’re facing up. Continue rotating the crankshaft until the T mark lines up in the inspection window again

Honda TRX 400 top dead center

Honda TRX 400 cam timing

Step 6. Once the motor is at TDC, look for the two marks on the cam timing sprocket. The two marks should be aligned with the face of the cylinder head for the timing to be correctly set.

Honda TRX ATV cam timing

Step 7. If the marks are not level with the cylinder head, you'll need to reset the TRX400EX’s cam timing. To do this, remove the two bolts holding the camshaft. Lift the timing chain off the timing sprocket, then the timing sprocket off the cam and rotate it so the two marks align with the cylinder head. Replace the timing sprocket back on the cam and the timing chain back over the sprocket.

Honda TRX400EX cam timing set

Step 8. Reinstall the two camshaft bolts and rotate the crankshaft counterclockwise until the engine reaches TDC again and the T mark on the flywheel is centered in the inspection hole. Check that the two marks on the cam timing sprocket are correctly aligned and if they aren’t, repeat Step 7.

Honda TRX400 camshaft bolts

Honda TRX400EX Reassembly

Step 9. Reinstall the cylinder head cover onto the motor. 

Honda TRX400 set cam timing

NOTE: Use a new cylinder head cover gasket when reinstalling the cover.

Step 10. Reinstall the top motor mount bolt and spacers, air intake, engine cover beneath the fuel tank, the fuel tank, plastics and the seat and you’re done.


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