ok noob petcok question...

PRI is to PRIME THE CARBS WITH GAS :?:

Is that correct or not? Wat is the PIR setting for exsactly?
I used that setting to drain the tank of its old gas...and i figured that the settin gis to prime the carbs with gas before startup? Is that right or not? PLEASE ADVISE!!!???? :?:

 

im trying to figure out the positioning of the petcock too if i point it up it bucks untill i switch it down same vica versa its pissing me off what way do i aim it to run the bike?

 

The prime setting bypasses the auto fuel shutoff valve. ON and RES require engine vacuum to let fuel flow. If your carbs and petcock are in good working you rarley need the PRI position except to fill the carbs after service or to drain the tank.

 

When the tang on the fuel valve covers the PRI, ON or RES on the petcock, thats what the function is. The tang pointing up is the OFF position. Run your bike on ON until you need reserve.

 

hmm ok so I shouldnt set it to PRI to prime the bike before starting????
I thought thats what it was there for? The only reason thats there CANT just be for servicing the carbs?

 

ok mine doesnt say anything on it just pri so thats what i was asking so down is on but mine bucks and misses when pointin up or down till i switch it to the opposite no matter what i just did a wot ride for about 20 min with it pointing up and it didnt stall does thiss mean my petcock is screwed cause sometimes it only wants to run in up position others it will be down

 

Generally you don't need to switch to PRI to start the bike unless it has been sitting for several weeks or more. Although some do it, I find that I need it after my bike sits in the 100 Deg heat for the day when I am at work. PRi is there for carb service but it is not used often. It also comes in handy if your auto fuel valve sticks closed.

 

ah fuel valve sticking i guess thanks man

 

OK:

You have three positions. Here they are with descriptions. These apply to the XJ-series petcocks, which have VACUUM OPERATED petcocks.

ON:
Fuel will flow from the gas tank only if there is more than 2 inches of gas in the tank or so, and suction is applied at the vacuum port. There is a raised "straw" sucks from that level in the tank, if it's below that level, it won't come in.

RES (reserve):
Same as ON, but will accept gas from the bottom of tank, not just from the raised position of the straw.

PRI (prime):
Allows gas to flow freely, regardless of vacuum, from the bottom of the tank.

Vacuum is normally supplied by the vacuum port on the #2 or #3 carb while the bike is running--but when the bike isn't running, there is no vacuum, so the RES and ON positions effectively both become "OFF" when the bike isn't sucking in air/when the bike isn't running.

PRI is only used on these bikes if your carbs are empty and you need to fill them up without a vacuum--as in, you emptied the carbs (when you took them off and serviced them, or drained them for some other reason, or the gas from them evaporated, whatever), and need them to fill up even though the engine isn't running.

The bike should not be left in PRI unless there is something wrong with your petcock and as a temporary measure it is used until you replace or repair the petcock--this is because allowing the petcock to supply fuel to the carbs while not running can allow a sticky float to flood the airbox (and thus crankcase/oil reservoir). The beauty of the "ON/RES" on these bikes is that they are automatically "OFF" when the bike is off, so you 'set and forget'.

 

All the 550/650/750/900 XJ's came with only a 3 position On/Pri/Res fuel valve. The XJ 1100 was the only bike to recieve an actual Off 4th position on the selector. That is why there is such an issue with the petcocks flooding the crankcase with fuel when the vacuum valve fails.

If you run the bike daily the you should not need to use anything beyond the ON/Res postions. If the bike is allowed to sit for several days. It makes starting easier to use the Pri position to make sure the bowls are filled first. Once the bike is runnig switch back to the on position.

Hash
It sounds like the vacuum valve in your petcock is sticking, or going bad. If you switch it from on to res. Then imediately switch it back to on again. Does it continue to buck?

Ghost