Honda CRF450R Piston and Cylinder Installation

Welcome to the piston and cylinder installation portion of our CRF450R engine rebuild project. We chose a Wiseco kit for this Honda motorcycle engine rebuild.

Watch the video above and follow the steps below to do a piston and cylinder installation on a Honda CRF450R.

Tools and Supplies Needed - Honda CRF450R Piston Installation

NOTE: The tools listed above are just the specialty tools, which you’ll need along with standard tools found in a toolbox such as a torque wrench and flathead screwdrivers.  

Honda CRF450 Piston Installation - Ring Gap Measurement

The Honda spec for a ring gap is between 10 and 12 thousandths. However, we installed a Wiseco piston, which has its own specs and behaves a bit differently than the factory Honda piston. 

Honda CRF450 piston installation ring gap

The dirt bike application we worked with calls for a bore times .004, for which we needed to convert our 96 millimeters to inches, and that works out to 3.78. With that multiplication, the Wiseco gap spec called for .015 inches, or 15 thousands, a slightly bigger gap compared to the Honda spec. 

Honda CRF450 Wiseco piston ring gap measurement

Honda CRF450 Wiseco Piston and Cylinder Installation

Step 1. Use a feeler gauge tool to measure the ring gap on the top piston ring, and a ring gap end grinder clamped down in a vise at a perpendicular angle to file down the ring up to spec (a couple of thousands in our case).

Honda CRF450 piston installation ring gap measuring

Honda CRF450 piston ring filing

Step 2. Use a file to chamfer the edge of the top piston ring to remove any filings left over from the grinding. This helps clean the ring up and smooth out any sharp or jagged edges.

Honda CRF450 piston ring filing

Step 3. Place the top piston ring into the cylinder, and use the piston to square it up so you can measure the ring gap.

Honda CRF450 engine piston ring gap

Honda CRF450 engine rebuild piston ring

NOTE: Repeat steps 1-3 if the ring gap is not up to spec.

Honda CRF450R engine rebuild piston ring gap

Step 4. Use a marker to label the piston for the orientation you’ll be installing the top piston ring, the oil ring and the rings that hold the oil ring in place. 

Honda CRF450 engine rebuild Wiseco piston

Wiseco piston rings Honda CRF450R

NOTE: The Wiseco diagrams call for the top ring pointing toward one end of the piston wrist pin, with the second ring going over to the other side. Wiseco’s setup has two rings: a top ring and an oil ring. However, we went with what Honda recommends, which is the top ring facing toward the exhaust side, and the oil ring and the two rings at the top and the bottom that hold it in place, which we labeled as O for O-ring, and I and II for the top and bottom support rings.

Step 5. Place a rag or a towel around the connecting rod to prevent the wrist pin circlips for the piston from falling into the bottom end, then lube and attach the circlips on one side of the piston’s wrist pin opening. 

Honda CRF450 piston wrist pin circlip

NOTE: The Wiseco orientation is marked pointing toward the exhaust side. On a factory Honda piston, it actually has an end for the intake on one side, so don't do it backward. 

Step 6. Put a little bit of assembly lube on the surface where the wrist pin is going to be and on the connector rod.

Honda CRF450 piston wrist pin assembly lube

Step 7. Insert the wrist pin into its slot on the piston, then attach the piston to the connector rod and the wristpin circlip onto the other side. 

Honda CRF450 engine rebuild piston assembly

NOTE: Be careful when pushing against the piston, as you don’t want to scar it up. Use a cloth to protect the piston while you’re seating the circlip into place.

Honda CRF450R engine rebuild piston installation

Step 8. Install the oil ring onto the piston, making sure the ends of the ring butt together and don’t overlap. 

Honda CRF450 piston oil ring

Honda CRF 450R engine rebuild piston install

Step 9. Install the top and bottom oil ring support rings, which hold the oil ring in place. 

Honda CRF450 piston install oil ring

Honda motorcycle engine piston installation

Step 10. Add a little bit of oil all the way around the top piston ring with your fingers, then install the top ring onto the piston with the end mark facing up.

Honda CRF450 piston ring

Honda CRF450 Wiseco piston installation

PRO TIP: Use a piston ring installer tool for this step if you have one, otherwise just pull the ring the minimum amount to get it to clear.

Honda motorcycle Wiseco piston installation

Step 11. Wipe a light layer of oil on the piston, especially on the skirts.

Wiseco piston

Step 12. Clean the cylinder with some contact-brake cleaner, and then wipe the inside of it with a thin layer of oil on a cloth. 

Honda CRF450 cylinder preparation

NOTE: Don’t glob a bunch of oil in there, as you’ll want a certain amount of friction on startup to get the rings to seat properly. 

Step 13. Install the dowel pins and the water pass collar.

Honda CRF450 engine cylinder dowel pin

Honda CRF450 cylinder water pass collar

Step 14. Gently install the cylinder gasket, followed by the cylinder itself. 

Honda CRF450 cylinder head gasket

Honda CRF450 engine cylinder installation

NOTE: Take your time while installing the cylinder and don’t force anything.

Step 15. Bring the chain up and seat it, then install the 8mm flange bolt on the side that holds the cylinder in place and torque it to 7 foot-pounds.

Honda CRF450 cylinder install chain

Honda CRF450 engine rebuild cylinder install

Step 16. Bring the engine up to top dead center and you’re done with the piston installation.

Honda CRF450 engine top dead center

The next step in our CRF450 engine rebuild is the head installation and the valve adjustment. Watch the video below to see how to install the head and adjust the valves on a Honda CRF450 motorcycle. 



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