Honda Rancher 350 Top End Rebuild Part 2: Piston & Cylinder Installation

Welcome to the second part of our Honda TRX350 top end rebuild, in which we reassemble the piston and install the cylinder after tearing down the engine. 

Watch the video above and follow the steps below to do a piston and cylinder install on a TRX350 Honda ATV. Use our Honda TRX350 parts diagrams for additional reference.

Parts - Honda Rancher 350 Piston and Cylinder Install

• Cylinder gasket
• Piston
• Piston ring set
• Piston pin
• Piston pin circlip

Honda TRX 350 Piston & Cylinder Install

Step 1. Install the piston pin circlip that faces forward into the piston. Make sure the circlip’s end-gap is at the top so it’s as far away from the small cutout in the piston pin hole as possible.

Step 2. Install the piston rings. The rings must be spaced so that their end-gaps are 120 degrees from one another (see illustration below). Install the piston rings in the following order:

a. Corrugated oil ring into the lowest groove in the piston.

b. Lower oil ring beneath the corrugated oil ring with its end gap about 1 inch to the left of the corrugated ring’s end gap.

c. Upper oil ring above the corrugated oil ring with its end gap about 1 inch to the right of the corrugated ring’s end gap.

d. Second piston ring into the middle groove in the piston. Make sure the second ring’s end gap is 120 degrees to the left from the corrugated oil ring’s end-gap. Also make sure the markings on the second piston ring are facing upward.

e. Top piston ring into the upper groove in the piston. Make sure the top ring’s end gap is 120 degrees to the right from the corrugated oil ring’s end-gap. Also make sure the markings on the top piston ring are facing upward.

Step 3. Put a drop of oil on the piston pin and the pin’s housing in the piston itself. Place the piston over the connector rod and install the piston pin. With the piston pin in place, install the remaining piston pin circlip, once again keeping the circlip’s end-gap at the top.

PRO TIP: Put a rag around the connector rod to prevent the circlip from accidentally falling into the engine.

Step 4. Lube the piston rings and the piston with engine oil, and double-check that the piston rings’ end-gaps are in the correct places.

Step 5. Install a new cylinder gasket over the cylinder studs, then lube the cylinder bore with engine oil and lower the cylinder head down over the cylinder studs. Carefully feed the piston rings into the cylinder bore with your fingertips.

NOTE: Be very careful and patient when feeding the piston rings into the cylinder so you don’t bend any of the rings or scar the inside of the cylinder bore.

After the Honda TRX350’s piston are assembled and the cylinder is reinstalled, the next step is to lap the valves and reinstall the engine head. Watch the video below to continue with the Honda Rancher 350 top end rebuild: valves and head preparation.