1997-2001 Honda CR250 – Top End Service – Part 11: Piston Installation

Sep 5, 2018

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How To Install The Piston On Your 97-01 Honda CR250

The Tools You Will Need

Feeler Gauges
Small Pick
2-Stroke Oil
Assembly Lube

The Parts You Will Need

New ’97-’01 Honda CR250 Piston Rings
New Piston Pin Clips

If you are installing a new piston, I suggest a Pro X piston kit. It’s a cast piston, so it’s a little heavier than forged, but it costs much less. Pro X is distributed and supported by Wiseco, so if you have any questions, you can just call.

I already put together an article covering piston selection, so I’m not going to go into that here, but a cast piston works for me because I will be installing it in a bike I use for enduro.

OEM – $75
Pro X (Cast) – $85
Wiseco (Forged) – $122
Vertex (Cast) – $138

Pre-Service Notes

I recommend opening the Service & Torque Specs in a new tab for easy reference.
If you need parts and tools, make sure to buy them here!
Pictures with captions are after the steps below.
If you need any help don’t hesitate to ask!

Gap Your New Rings

Before we install the piston rings, we need to make sure the end gap is within spec.
Place each ring into the bottom of the cylinder, and push it down with the piston.
Measuring the ring gap with a feeler gauge.
The end gap on both rings should be no greater than 0.026 inches.
If the rings are too tight, you can file the ends with a fine metal file until they are in spec.

Place each ring into the bottom of the cylinder, and push it down with the piston.

Measuring the ring gap with a feeler gauge.

The end gap on both rings should be no greater than 0.026 inches.

Pin Clip Install

Install the first piston pin clip into the pin bore groove.
Your thumbs and a small pick should work just fine, but be careful not to gouge the cylinder with the end of the clip.
Rotate the clip, so the opening faces up.

Install the first piston pin clip into the pin bore groove.

Rotate the clip, so the opening faces up.

Piston Ring Installation

Double-check that the rings are clean and dry.
Lubricate the piston edge and ring grooves with 2-stroke oil.
Check that the IT mark is facing up, and align the bottom ring with the alignment pin.
Spread the ring just enough to clear the piston, and install straight down, do not try to wrap the ring into the groove.
Check that the ring is free in the groove.
Repeat for the top ring.
We are using oil to install the rings, but the oil needs to be thoroughly wiped off afterward.

Check that the IT mark is facing up, and align the bottom ring with the alignment pin.

Spread the ring just enough to clear the piston, and install straight down, do not try to wrap the ring into the groove.

Piston Installation

Lubricate the pin and pin bore, and press the pin into the open side of the piston.
Apply assembly lube to the connecting rod opening, and install the needle bearing, then apply lube to the inside of the needle bearing.
Position the piston over the connecting rod, so the IN marking is facing the rear of your bike.
Press the pin through the connecting rod, and seat it against the pin clip on the other side of the piston.
Install the second pin clip with the opening facing up.
Before you move on, place your piston holder to keep it in place.