1982 Gs650l

[Burke1959]

My wife and I have just purchased a 1982 GS650L. This is a return to cycling for me after 12 years off and a first bike for my wife. The bike cost $800.00, has a new set of tires and runs well.
Questions:
The petcock has three labeled settings:
1.) RES
2.) ON
3.) PRI
My assumptions are:
There is no "OFF".
The petcock should be set at PRI when starting cold.
The petcock should be set at ON for driving.

I don't have a manual yet (just got the bike home a few days ago) -- am I correct in my assumptions?

[Billy Ricks]

You got it. The petcock is vacuum actuated. As a precautionary measure pull the vacuum line off and make sure there is no gas present in it and suck on it to see if it holds vacuum. The diaphrams in these petcocks sometimes leak which can lead to unwanted gas in the crankcase.

[Burke1959]

1982 GS650L petcock

Thanks, I left the petcock in the PRI position the first night after I got the bike in the garage and opened the garage door to the smell of fuel. Not a lot but there were some puddles on the engine case. Leaving the petcock in the ON position solved this problem.
So PRI does not have a vacuum to hold fuel back? PRI simply opens the line from the tank to the carbs?
I am attending little problems as they arise so want to know if there is an issue with the petcock I need to address regarding a small fuel leak with the petcock left in the PRI position for a good 18 hours.

[Billy Ricks]

Thanks, I left the petcock in the PRI position the first night after I got the bike in the garage and opened the garage door to the smell of fuel. Not a lot but there were some puddles on the engine case. Leaving the petcock in the ON position solved this problem.
So PRI does not have a vacuum to hold fuel back? PRI simply opens the line from the tank to the carbs?
I am attending little problems as they arise so want to know if there is an issue with the petcock I need to address regarding a small fuel leak with the petcock left in the PRI position for a good 18 hours.

In the prime position there is a small rod inside the petcock that pushes on the diaphram in the same direction as vacuum pulls it. It opens a passage allowing fuel into the carbs. If you had leaking fuel after leaving it on prime you have a float problem in the carbs. Either a sticking float or most likely bad o-rings on the float valve seats.

[kalessin]

Under normal circumstances, you only need to use the PRI setting if your carb bowls have emptied (i.e. you drained them or the bike was sitting for a long time).

Leave the petcock on "ON" for most circumstances, including parking overnight. It's a good idea to run into your "RES" reserve from time to time, to use the gas in the bottom of the tank (water can build up, etc).

The carb overflow from leaving the petcock on "PRI" overnight is relatively common, it doesn't necessarily mean you need to pull the carbs and fix the float levels. (Think about it, if the float shutoffs could do the whole job, why would we bother with petcocks that shut off at all, except to remove the fuel tank?) My GS1100GL will overflow the carbs if left on "PRI" overnight, but has done just fine for five years with the petcock kept on "ON" or "RES".