Running thread of my search for Petcock rebuild parts - this petcock has one side riveted (the switch side) and one side (diaphragm side) serviceable.



1. Upper and Lower petcock extension block o-rings (one on the tank, one on the petcock - 28.5mm x 2mm / 29.5mm x 2mm

2. Parts Unlimited 0705-0467 Petcock rebuild (includes main bolts, 4 diaphragm screws, diaphragm and spring, upper and lower extension block o-rings, control switch screw




3. Niche Cycle PRH-11013 - petcock diaphram rebuild kit - contains spring, diaphragm and lower o-ring (but missing tank side o-ring and screws).




OR

If you can find it (you probably can't!)

4. 16950-MZ2-790 PETCOCK ASSY - complete petcock including strainer - out of stock worldwide.

5. Rivet (switch side) main oring - 28.3 x 1.78mm

 

As a note, I replaced the main o-ring (the one behind the selector) thus:

1. strip the vacuum valve off the petcock
2. drill through the center of the rivets on the dial side for M3 (2.5mm) down 3/8 from the surface of the rivet - use the indent of the rivet as a center guide and a pillar drill to go straight down. One side you will have a blind hole, the other you will go clear through the casting.
3. drill off the head of the rivet with a large bit - 10 or 15mm. You want to remove the head without marking the plate. Go careful, the rivet is softer than the plate so you have some leeway.
4. pry off the plate gently to expose the guts. Remove the ball and spring but note what position it goes in.
5. Tap for M3 - I clamped the petcock to my drill press table so the 2.5mm drill bit went perfectly into the hole I'd made, then I substituted the drill bit for a tap center so I went straight in - you may be better at hand tapping than I, but remember, this is a one-time opportunity. Again, one side you'll tap through the casting, one side you tap into a blind hole.
6. replace the ethanol-destroyed main o-ring with a 28.3 x 1.78mm ring (be super **** about cleaning everything!)
7. If everything went well above, you'll be able to snap the cover back on and it will stay there on the old rivet heads, then you can insert a couple of M3 screws into the holes - one about 1/4" for the bind hole, one 3/8" for the through-hole. Put a M3 washer on as well.

Done!

After all this, my petcock stopped leaking - but I realized it was on or not-quite-off. The internals are shot, but it's not leaking fuel over the exhaust any more so that's a bonus!

 

Yeah, you typically have to look at seat where plunger/diaphragm seals. Might need to clean off corrosion so it's smooth. Also stretch spring lightly to increase preload force.