gas tanks & petcocks

[BklynMatt]

I just did a valve job last summer & completed the job mid fall, I opted not to fuel & fire to leave it all winter. OK now I'm starting upp & I 'm putting the tank on & I see the Petcock(81 xs) has 2 nipples but the tank doesn't have any way of attachment from the other side, is the reserve plumbing internal? How does the gas get from the other side?
Next I realixe when I took off the tank I'm sure I only took off the 1-tube from the Carbs.
I guess the horizontal Nipple should have a "Y" connection which feeds both nipples into 1-line
But I'm guessing & I cant find any answers to Bothe these questions in Haynes

I'm sure experienced people will find this quite funny, but I would appreciate any guidance
Matt

 

[inxs]

- youve probably got a vacuum operated petcock...78-84 North Am 650's have, as original, vacuum operated petcocks linked to the intake-carb holder or boot
- these leak and are a pain to repair
- better to get a non-vacuum earlier style petcock and blank off the vacuum source

 

[BklynMatt]

Let me give a little more info, on the petcock there is a 6 o'clock & a 3-o'c nipple the 3-oc never had a line that I recall, prior to the Valve job i had no issues with leakage I just can't remember the hook-up to the carbs. I'm assuming that the 3-oc is from the reserve.
The vaccuum is generated by the carbs no?
I'm trying to get things operational as stock b4 i try modifying,
Thanks for the reply though

 

[xjwmx]

The pipe pointing toward the center of the bike is the gas outlet. The pipe pointed toward the front is the vacuum inlet. The vacuum for it comes from the barb on the left intake. The carbs are joined by a T one gas like feeds both. The reserve comes from two lengths of pipe inside the tank. When gas gets below a certain level it can't get into the first pipe and you must switch to reserve to route gas from the second pipe.

 

[gggGary]

And when the bike staggers to a stop because you just knew you could make it past one more gas station. You stop, lean it way over on the left side, and just maybe get enough gas to the carbs to make it a few more miles.

 

[BklynMatt]

thanks for the information
Much appreciated!

 

[nj1639]

Make sure the right hand vacuum barb is capped off.
If you go with an aftermarket standard petcock you can link the two barbs together with a bit of vacuum line.

 

[Ccrider]

75 650 with stock carb settup.
looking to use this newer tank with this vacum style petcock.
Can I just cap off the vacum line with no venting or flow problems?
Run the single fuel line to a splitter to feed both carbs

 

[gggGary]

Ccrider;75 650 with stock carb set up.
looking to use this newer tank with this vacuum style petcock.
Can I just cap off the vacuum line with no venting or flow problems?
Yes.

Run the single fuel line to a splitter to feed both carbs
Yes.

 

[XSLeo]

The only problem with running the later vaccum petcock is that you will only have fuel flow in the prime position. The on and reserve only work with vaccum. The prime position will not have a reserve and when you run out of gas, your out of gas.
Use the later tank, but get the manual conversion petcock from Mike's. That way you will have an on, off and reserve.
Leo