2nd hose on tank from petcock

[tdub78]

My 78' has an original fuel tank with a single petcock with 2 hoses - the RHS hose is the fuel hose - what is the 2nd hose on the left? And what should it connect to?

I've been through my Haynes (helpful but not comprehensive) and cant find any mention of the 2nd hose and where it should connect to.

Could this be part of my starting problem?

 

[jamesgs4]

It is the vacuum line for the petcock, is connects to the barb on the carb boot. The bike won't get fuel when in the on position without that vacuum line connected.

 

[nj1639]

There should be a barb on both carb boots. If you're running the stock vacuum operated petcock then the smaller diameter line connects to the left barb, the right barb gets capped off. If you go with a simple aftermarket petcock- on, off, reserve- then you can link the barbs with a length of hose or cap them both off.

 

[Nickyd]

i have the same petcock and am trying to put the tank back on so i can try and start my 81 xs650 SII. the original fuel filter is being used and i ant figure out where to put it so that the line does not crimp?? i am altering the gas line from the petcock to filter but would like to use the original line on the other side of the filter to the bike? any suggestions?
THanks!

 

[weekendrider]

Loosen the L-bracket on the carbs swing the "T" down.
Run the line from the T to the outside of left carb, add the filter and the line to the petcock. Gets it out where it easy to change on the road if necessary and makes the mess less in behind the carbs when you take them on and off.
Thanks to NJ1639 for the tip.

 

[Nickyd]

Ok great! So I need to make the hose from the carb longer and feed it out the left side of the bike?
Thank you? Do you have a pic?

 

[nj1639]

The last set of bs34's that I turned the 'T' on I just got ahold of it and turned it down.....no leaks so far. A bit of longer hose coming out of the T going down and out the left side of the bottom of the carb, into the filter. Then from the filter up to the petcock. I'm running aftermarket petcocks that require the adapter plate and a bit of filing of the tanks petcock hole to accept the round wire mesh 'in tank' filter that's on the petcock. The stock petcocks have an elbow in them which wants to direct the fuel hose to in between and above the carbs.....could be an issue. Here's an archive pic that may give a hint as to what I've done.....

 

[Nickyd]

Ok thx! So does is matter if I do that with the stock vacuum
Petcock?

 

[nj1639]

Might have to re-angle the stock petcocks outlet.