That’s right, it’s top end time!
I finally hit my 20,000 mile goal, which is when I told myself I would tackle the top end with new OEM piston, rings, cylinder, and gaskets. Taking the cylinder and piston out took as long as it took to clean up the old gasket, not sure if that’s saying the top ends are easy work or Honda’s gaskets are a nightmare to replace… probably both…
Looking at the old piston, beside some expected carbon buildup it was in fantastic shape, like new! This was expected though, I keep on top of regular maintenance, haven’t done anything like a big bore kit to stress stock parts, and out of curiosity I did a compression test before opening it up and was at 150psi, which increased to 163psi with a bit of oil. Service manual says 160psi is good so I was right on point. Cylinder was pretty flawless too. Just goes to show how bulletproof these bikes are with the proper maintenance.
Got the new piston into the new cylinder off the bike for ease then slid everything together. Install was nearly as smooth as tear down, although admittedly I was dumb and accidentally put the first gasket on upside down and didn’t realize anything was wrong until seeing that the screw holes didn’t line up on the cam side. Annoying to have to take off and put on a piston twice, but had to be done.
After setting the cam at top dead center, checking the valve clearances, adding oil, and installing a new exhaust header, I fired the bike up and all sounds well! Had a little bit of nerves having never replaced a grom top end, but I’ve done plenty of other top ends in my day on other bikes and all have ran perfectly after install. Patience is key, and when in doubt take it out on something that isn’t a part of the bike (garage stress ball maybe?).