I got fed up with trying to get the fuel cock working properly on my GT500, so I made up a test rig out of a large coffee can which made it much easier to trouble shoot and test. I used a spacer block from a GT750 on the inside of the coffee can so I could get a good gasketed seal on both sides of the tin and rather than gasoline/petrol I used mineral spirit (varsol/paraffin) - its just a lot safer. You can get an auto-ignition due to static electric build up from gasoline flowing through fuel lines into a catch container (obviously when testing you don't want it all over the floor) which could put a serious cramp in your day. I suppose you could use water, but then you'd have to get the valve dry before commissioning.
After a bit of Rick's trick with the bamboo chop stick end to burnish the valve seat, the addition of a viton o-ring seal on the pintle, slight adjusting of the spring tension and new gaskets and seals, all is now good !
Ian
If at first you don't succeed, just get a bigger hammer !
Dis you replace the diaphragm too? Mine is from another bike the P.O. used. It is working OK, but Iam looking to the future when it will be necessary for a re-build.
I did the very same thing years ago when rebuilding a GS1000 petcock. I use a model airplane fuel bulb to pull a vacuum, but lung power also works. I used plain old isopropyl (rubbing) alcohol for the test fluid. It's thinner than water and can be followed with gasoline immediately.
For those who don't know, a GS1000 (78 -79) petcock will work on a GT tank. The bolt pattern is the same. Single vacuum and single outlet.
I was born with nothing and still have most of it left.
rbond wrote:Dis you replace the diaphragm too? Mine is from another bike the P.O. used. It is working OK, but Iam looking to the future when it will be necessary for a re-build.
No - I was lucky enough to be able to use the old diaphragm. I do Like Coyote's idea though - full rebuild kits for those, complete with diaphragms (!!!) are easy to locate.
Ian
If at first you don't succeed, just get a bigger hammer !
I suppose you could use water, but then you'd have to get the valve dry before commissioning. 
