Vacuum Petcock, where does the vacuum plug in?

[PhillyxsRookie]

Hello all,


My 1983 xs650 wants to run! I've been kicking the hell out of it and it will run for a few seconds or cough. It seems like its starving for fuel. The petcock on the bike is a vacuum line petcock (PRI/ON/RES). I just got it back from a guy who was checking the bike out and had it running and he has the fuel line connected to the left side of the petcock and nothing connecting to the right side of the petcock. Isn't there supposed to be a vacuum line coming out the right side and where do I run that vacuum line to? It seems to me like the bike isn't getting fuel at this point. I have about a gallon of gas in it. I know lots of people advocate the non-vacuum petcock, but this one isn't leaking so I don't think I need to replace it. Thanks.

Whew, my kickin leg is tired.

 

[payaso13]

Mine has a line from behind both petcocks to the carburetor barbs on each side if carbs

 

[PhillyxsRookie]

Hmmm. i only have one petcock on the left side. I've checked out the carbs and i think my "barbs" stick out from under them. I'll try hooking the vacuum line to one of them tomorrow and see what happens.

 

[xjwmx]

On the left carb holder (rubber ring between the carb and head) there's a little brass pipe sticking out. The vacuum for the petcock goes there. The identical thing on the right carb holder should be kept capped; 1/8" ID vacuum cap works.

Best as I recall the pipe from the petcock that goes toward the center is the fuel and one that goes toward the tank is the vacuum.



In the meantime...if you want to ride or test some theory, just run it on prime. But don't run out of gas somewhere. Cover both brass pipes if you (hopefully) have them. Use 'run' as off.

 

[5twins]

The larger nipple on the petcock is for the fuel line. It usually points to the rear. The smaller nipple, usually on the back side of the petcock and pointing forward, is for the vacuum line. It hooks to a barb on the intake manifold like so .....

This is the right side on my '78 which has two petcocks and two vacuum lines. Your single petcock set-up will be on the other side, hooking to the barb on the other intake manifold.

 

[PhillyxsRookie]

Thanks! I'll let you know if that was the issue!

 

[angus67]

you say you want to keep your vacuum petcock because it isn't leaking, but.........it also isn't working.
nothing wrong with getting a manual petcock, unless your doing a concourse resto.

 

[PhillyxsRookie]

Ok, with the petcock to PRI I can get it started with the throttle half open. As soon as I let off the throttle it cuts back and dies. I can't get it to Idle. Also there's a bit of smoke and some pops. I did spray some starter fluid in there the other day, but I'm thinking its a carb problem. The carbs were rebuilt (by someone else), so I'm curious as to why it's not running correctly. Any suggestions?

 

[PhillyxsRookie]

I have straightpipes and k&N airfilters on there, so I'm going to play with the carb idle sync and see what happens

 

[Oliver Torres]

To the question of the popping sound the bike makes. check if its the rubber mounts. just saw a Utube video about it. you can check yourself by spraying carb cleaner on the mounts when its on and if the idle changes its going to be the mounts!

 

[Oliver Torres]

If their are cracks in the mounts it will let air in and change the air/fuel mixture and create those pops, and cause problems with idling. Even if the cracks are small the rubber mounts can let air in.