1980 GS750ET stock petcock question

[pdqford]

Could someone please help me out.
I never know where the normal and prime positions are.
So I leave this thing right where it shows in the attached picture.

I just installed my freshly cleaned tank and have added 2 quarts of fuel.
Don’t want to add more fuel until I’m sure the tank won’t have to come off again.

So which way should I twist that little white dohicky to put it on prime?
(And is it now correctly positioned for normal riding?)

Thanks in advance for any help.........Jim

[hampshirehog]

Prime has the slot at 12:30 and 'not prime' is at 3:15 (if you imagine the hands of a clock). Your photo shows it on prime.

you can turn it both ways, clockwise or anti-clockwise - it makes no difference to function.

[Nessism]

Function is described in the factory service manual too. You need a pulse of vacuum and functioning check valve (in the back cover) or the prime feature won't work.

[pdqford]

Thank You @hampshirehog and Ed. I ended up pulling the tank off (again) and took the fuel valve apart. (I had it off when I cleaned it and the tank but could no longer remember what it looked like in there.

The o-ring seems to be in good shape and sealing good. I wanted to take diaphragm off the base of the unit so I could see what that little twister shaft does when set to prime, but the gasket was stuck pretty good to the base of the unit so I had to leave well enough alone.

I see how applying a vacuum pulls the o-ring off it’s seat to let fuel drop into the carbs. So I rotated that little twister shaft expecting to see it pull the o-ring down when the shaft was in prime position, but didn’t see any motion of the o-ring at all.

So while the tank is off I poured a little fuel into the gas line to fill the carbs, put the tank back on, hit the starter and it came to life!

(Now I ‘m back to where I was last fall - the @#$& tach acts like it is full of STP and has all it can do to get past 2000 rpm and takes a full minute to come down to zero when I turn the engine off! Guess I’m gonna have to take it apart (again)). Pdqford