really stupid question

[cowboy5]

the fule shot off valve has 4 settings, on, off, pri and res. which one should it be on when running the bike. i do not know what pri is. thanks....my last bike only had on off res.

please dont laugh at me for this really stupid question...thanks

[jjwaller]

Not Stupid

You have a vacuum operated fuel valves.
When the bike is running, the fuel flows when the valve is on.
Likewise, when not running the fuel does not flow.
The PRIME position, is to get fuel flowing to fill the carbs
if they do not have enough fuel to run the bike to generate
vacuum to operate the petcocks.

John

[cowboy5]

so it should be on on. only on prime to start it?

[Rasputin]

You should only need prime when the carb bowls are empty. If it has been sitting a long time or you worked on the carbs. Other than that it should start and run in the ON position.

[cowboy5]

thANKS

thanks, that explains my issues this smorning of a stall. i filled the tank yesterday after sitting empty all winter. i put it on run. it ran for a while and shut off on the highway. i then moved it to prime and it ran again. i will now move it back to on. thanks a lot

[DGXSER]

No such thing as a stupid question,

Your just ignorant Just like I was a couple months ago which simply means you don't know...yet. If it needed priming, it would not have started. Once the bike is running, the ON position should keep it going just fine as you are creating vacuum once the bike runs. Like Rasputin said, the Prime is only when the carb bowls are low or empty, if it started, they are not.

I think the XJ has the "octopus" like the specials in earlier years. If so, what you described is more of an octy problem. The fuel flows from the petcocks to a vacuum operated fuel control valve mounted on top of the carbs between 2 and 3 that then delivers fuel to the carbs when the engine is running and pulling vacuum via a vacuum line to the no 2 intake boot vacuum fitting next to the head. Mine was not working right and I had that same problem. Had to run with petcocks in prime all the time. In my case, a PO had kinked the vacuum line when installing it. I pulled the Octy anyway to eliminate the issue, that I got out the scalpel without looking at the simple solution and dorked up the seal so it leaks. I just turn the fuel off at the petcock when done riding.

BTW, when running in prime position you eliminate your reserve function, if you run dry, your dry, no reserve gas.

[John]

If the petcocks have four positions, On, Off, Prime and Reserve, then they are not the vauum type, but they are the manual type found on a Special or an XJ. Fuel will flow from the foward port in the res position, and from the rearward port when in the on or reserve position. When looking at the petcock from the side, the handle should be pointing down for on, up for reserve, to the rear for prime and forward will be the off position. The problem almost sounds like the petcocks are set in the wrong position when it tacts like it is running out of fuel. Another thing to look for... is the L or R that is cast itno the petcock handle, distingushing right from left. They may have been switched around.

[DGXSER]

I just learned, or confirmed something. Thanks John. I thought the vacuum operated petcock was a standard only item, and they only had three positions, no prime.

[Ken Talbot]

Just to be sure you've got it:

Standard petcock
- vacuum operated
- three positions
- on, reserve, prime

Special petcock
- vacuum control provided by octopus, not within petcock
- four positions
- on, off, reserve, prime

[DGXSER]

Ahhhh, thanks for that clear up Ken!

That would totaly suck to not have an off position.