complete noob - petcock positions

[whiteboyslo]

OK, be easy on me. first bike.....

what are all the positions on the petcock of my 79 GS1000? the bikes i've ridden before this one (all 2 of them) had an 'ON', 'OFF', and 'RES'. OK, i get that. On my bike, however, there's a 'ON', 'RES', and some other position that escapes my mind right now. I understand that 'ON' is, well, on. 'RES' is reserve, as in 'i should really be looking for a gas station now', but what is that last position for? do i not have an 'OFF'? which one should the bike be in while not being run? what are the inherent dangers/problems of not leaving it in the correct position?

Mike

 

[CA180]

The last position is prime. Its for when the carb bowls are empty. But you dont want to leave it on prime because it will fload your carbs and leak out if left un-attended.

 

[whiteboyslo]

what are the scenarios in which the bowls would be empty? is this a setting i should leave it in when, say, it's been a few hours or more since i rode it?

what position should the bike be in when it's sitting for the day?

Mike

 

[relic-rider]

There is no OFF. This is a vacuum actuated petcock and it opens up when the engine is cranked and running. The On position is normal riding. The Res is when you run out on the ON position. You have a little less than a gallon left. The last position on some GS's is PRI or prime. Gas free flows from the petcock to the carbs constantly and does not shut off. This is used to fill the float bowls after the bike has been sitting for a while. Don't leave it in prime while riding or parked. The needle and seat in the carb may not seat and gas may overflow onto the ground, into the airbox, or into the cylinder. Some GS's only have On and Res. No Prime.

 

[whiteboyslo]

so, when sitting, 'ON' or 'RES' is acceptable? and prime should only be used if, say, i'm having a tough time starting the bike?

Mike

 

[CA180]

More or less, prime is for when youve run out of gas and just re filled the tank. OR is you just took your bike out of storage (hopefully you drained the carbs) and you need to fill the bowls to get her going.

 

[whiteboyslo]

ok, went out and checked the bike. i've been running in prime for at least the last day. could that be causing this?

http://www.thegsresources.com/_forum/showthread.php?t=109857

man, i hope so. i'll gladly fess up to a newb mistake if it gets thsi bike back to running like i know she should.

is there anything else i should do, or anything else i possibly damaged by running it this way?

Mike

 

[CA180]

Only things i can think of would be wasting gas, and if it sat too long pumping gas in there it could wash down into the case. That would cause dilluted oil. I'm sure others will chime in.

 

[relic-rider]

Running it in prime probably isn't causing your problem. What you need to do first is to check the operation of the petcock. Remove the hose to the carbs, put it on "on" position. No gas should flow out. Then either crank the engine over slightly or remove the vacuum hose from the carb and suck on it. Gas should flow when vacuum is applied to the petcock and shut off the flow when it stops. Do the same with it in Res position. Should work the same way.
Also note if there is any gas or gas fumes in the vacuum hose to the petcock. If there is, the diaphragm may be may have a pinhole and is leaking gas into the #3 carb, causing a rich condition. The petcock has a screen inside the tank that may need cleaning, or replacing if it is damaged. You normally don't need an inline filter if this one is in good shape. It tends to restrict the flow if you have the wrong one or too small of a gas line. Use 5/16" ID hose otherwise you may starve the carbs if something gets plugged.
And don't run it for any length of time in prime, especially when you stop the bike. The carb needles are really not made to hold back the pressure of a full tank of gas, and can leak gas into the overflow lines or airbox or can fill your cylinders and crankcase with gas. Also if you ride that way, when you run out of gas, you have no reserve.