Topic: Anyone know how to repair a riveted petcock?

[Kelvin8]

I finally got my carbs back and installed, (need tuning!) on my '78 550K. However, my petcock leaks in both the on and reserve positions, but not in the off position. It's hard to find replacements, so how do I fix the one I've got? I know I have to drill off the rivets and drill and tap threads for screws, but do I just open it up and see what's broke and fix/replace/manufacture new pieces? OR can I use replacement parts for a screw together petcock?

[Gordon]

I believe David Silver spares sells that petcock, if you want to go that route. 

[Bodi]

So it leaks fuel and drips from the lever area I assume. Opening it up and seeing what's wrong is the first step. The actual valve is probably a plastic cone thing seated in a conical hole, a bit of silicon grease helps it seal and move freely but won't fix bad scoring; if it seals in OFF then you are probably OK. Some petcocks use a flat rubber disc to do the valving, sometimes this can be flipped over to renew the action if the sealing ridges are worn off (it looks like both sides were made identical so the assemblers couldn't put it the wrong way up... so there's a new unused surface for us).
As I recall there's an O-ring in there that seals the lever and stops external leaks. If it's not worn down or turned to rock a cleaning and dab of silicon grease may be all you need. You might find a "standard" O-ring that will fit in there.
I faintly recall from unfortunate experience that the cone type can be assembled wrong with the lever misaligned 180 degrees. Check that it works correctly before mounting it!
If it's repairable you've saved the cost of a replacement, if not you haven't lost anything.

[Robert]

Don't know what type of  petcock you exactly have, below you see a scan of the dismantled petcock (rivet type) of a CB 650, just so you know what roughly to expect.
I drilled out the rivets and tapped threads in instead (M3) cleaned everything and reassambled the lot, no new parts besides the screws and it did stop the leaking that I had before, but that won't work if the 4-hole gasket is broken.



Bigger pic:
http://img438.imageshack.us/my.php?image=1980cpetcocksmall1ed.jpg

[dusterdude]

those parts look a lot like 750 parts too

[Kelvin8]

Thanks guys,

You're all a great help. I guess I'll pick up an M3 tap before I start drilling.
BTW, I found a source for a new one, so if it's unrepairable ... or, I may get the new one and fix the old one ... just in case someone here needs it.

Kelvin

[Kelvin8]

My wife tells me to get the new one first.

[KB02]

I used to have an '82 Nighthawk 750 that had one of those rivited petcocks that leaked. In my case, the rubber o-ring around the lever was shot. I bought one off of ebay and when I installed it on the bike, it had the same problem. Well, not to be beaten by a petcock, I decided to drill it apart and take a look.

Since these are not "Rebuildable," you're not going to find any parts for them anywhere. Like Robert said, if it's the four whole gasket that leaks, you're S-O-L.  But, if it's the rubber O-ring, you should be able to find one that fits.

(The stock  o-ring is a squared bodies o-ring, but a regular round one works.. from my experience)

[dusterdude]

robert,that 4 hole gasket looks just like the one on my 750 k1,it might work on yours and btw your english is just fine,you need to learn how to talk american.

[Robert]

robert,that 4 hole gasket looks just like the one on my 750 k1,it might work on yours and btw your english is just fine,you need to learn how to talk american.

Thanks mate, er, dude (?)  I'll see what I can do.

I didn't find any "real" O-ring in mine, but I remember me suspecting the dirty nylon (or polyethylene) gasket on the very right handed side of the pic to be the source of trouble.