anyone have a guide to dismantling the frame petcock?  Im getting fuel to the tap but none out of it.
1990GS

I recently had that issue but took mine off the bike and used carb cleaner and sprayed through each port. You will see right through it. I dont believe there is a way to break it down to much more than it already is.

Have you got vacuum on the tap? Fuel won't flow from the"on" or "reserve" position without vacuum. It should flow in prime position though. It's easy enough to dismantle the tap. Just use a Stanley knife to lift the retaining clip. It's directly behind the tap handle. Just make sure you put it back together exactly the same way. There is a plastic cone behind the tap and it has a small slot in it. The tap will only fit in this slot one way. Just look at it closely as you dismantle it and take photos on your phone. It's easy otherwise.
The vacuum is on the the back of the tap. Just losen the screws and carefully remove the cover and diaphram.

took the back off and the diaphragm was in good shape but there was some black sludgy crud in it.  Did my boiling trick, then soaked in  soapy bath, then rinsed and its now drying.

Get rid of it.








Open and reserve lines to a T-fitting, reserve line has an on/off, outlet from the T-fitting has an on/off, through a fuel filter, into carbs...

No vacuum, no diaphragm, no problems.  I have a main on/off for when I park, and I have a separate reserve on/off for the reserve function.

thats really cool, thanks.

As I'm new at this....
1. what kind of on/off valves should I look for? (are the off a bike etc?)
2. Do I just block off the vacuum line to the carbies?

cheers
Jimmy

Otherwise was going to add that its all cleaned out and back together now but I won't reassemble until the weekend when my new battery arrives.

Got the on/offs off eBay, 1/4" straight ball valves.

The T-fitting was from a local parts store and so was the fuel line.

The spring hose clamps were from a local hardware store.


Vacuum on carbs is plugged.  Either kink and zip-tie the vacuum line if you are cheap/lazy or buy a rubber cap to stick on the vacuum nipple.

This is the second GS500 I've done this on and I love it!  I think it's easier to reach the reserve valve while riding when it's on the frame like that anyway.