I recently rebuilt my 350X petcock. I wanted to post the step-by-step instructions and parts required in case anyone else wanted a guide to follow. This is a repost of my original thread (from memory) which was a victim of the database crash, so it may not look exactly like it did the first time.
Honda Parts Required:
4-Hole Washer: 16955-HA2-005
X-ring: 16963-HB9-005
Tools Required:
Dremel with grinding wheel (or similar)
Drill bit (#39) and then when that breaks and the store is out of more, just get a 3/32"
3mm x 0.5 Tap
1000-1500 wet/dry sandpaper
Carb cleaner (I use Berryman's Carb dip in the gallon can)
Other Parts Required:
M3x0.5 pitch screws, 10 mm long (x2) I used SS button head screws. They are nice and low profile and use an allen head.
Rebuild Steps:
1. Carefully grind off the heads of the rivets holding the plate on the front of the petcock. Don't be too agressive, and try to stay off of the front plate.
2. Remove the front plate, followed by the flat washer, the wave washer, the lever, and then finally the old 4-hole washer. Take a look at the old washer next to the new washer.
3. Remove the old X-ring washer from the lever.
4. Now is the time to dump the metal parts (petcock body, lever, and front plate) into the carb dip carb cleaner to clean them all up. Once you're happy with the parts, take the lever and clean up the back side with a piece of wet/dry sandpaper (I used 1500). The back side of the lever is what seals against the 4-hole washer, so make sure it is smooth, clean, and polished (within reason). Mine was rough at first. The 1500 cleaned it right up. Be sure to wash off the lever really well when done.
5. Drill and tap the petcock body for the M3 screws. If you weren't too agressive in the grinding step (#1) you'll still have dimples in the center to help center the drill bit. Drill all the way through the body. Then tap the holes with the tap (always use oil with your taps). You could probably get away without tapping the holes, but you'd have to experiment with the proper size drill bit to use with whatever screws you are using. I like tapping the hole since it goes back togeher so nice. Again, wash this part really well to get rid of the oil and metal shavings.
6. Reassemble everything. Put the 4-hole washer into the body, follwed by the shut-off lever (with the X-ring installed), the wave washer, the flat washer, and finally the front plate. Use the screws to hold it all together.
Done!