carb and fuel questions 79xs650

[jolo9534]

hi guys so im going to install some mikuni carbs on my xs, question is im not really sure what i need. the intake boots have the barb on them, so when i buy an after market petcock, does it have to be the one that says pri on it, or can i just get a regular one, that is on off and res. been trying to find out myself before posting but theres just so much info out there, any help would be great thanks

these are the ones i got
XS650 Mikuni VM Roundslide 34mm Performance Carb Kit

 

[5twins]

No, you don't need vacuum petcocks. Just be sure to cap the barbs off on the intake manifolds if you're not using them. You'll have giant air leaks if you don't.

 

[gggGary]

there are two different bolt spacings on the stock tanks

Petcock bolt spacing
standards through 1977 42mm (non vacuum petcocks)
All Specials and 79 standards 46mm (vacuum petcocks)

 

[jolo9534]

where would they go if i didnt cap them off? im a noob and didnt take a photo of it before i took it apart.

 

[5twins]

They had hoses attached running to the back of your original vacuum powered petcocks. That's where the vacuum supply to operate those petcocks came from .....

 

[jolo9534]

k got it. once i sync the carbs then i can cap em like you said or replace them with ones minus the barbs

 

[fredintoon]

k got it. once i sync the carbs then i can cap em like you said or replace them with ones minus the barbs

Hi jolo.
vacuum line caps (even the good fuelproof ones) cost a dollar or so each and you can buy them anywhere.
The price of vacuum barb-free XS650 carb connectors will make your eyes go big and round plus you can only get them by remote purchase.
Most folks who own the early XS650s that don't have vacuum barbs tend to fit them into their carb connectors so they can balance their carbs more easily.
I capped one of my bike's vacuum barbs and used the other to trigger my ScottOiler, a device that IMHO no chain drive bike should be without.

 

[Brassneck]

You can also just use one longer vacuum hose and connect each barb to the other...Might even help balance the carbs a bit...once they are synced of course.

 

[jolo9534]

thanks for the replies fellas, ill probably just cap em off. im pretty excited bout the build i can see the end product in my head.