New '85 Maxim XJ700 Owner...looking for insight...

...on the petcock.

Hi friends. I recently bought a clean XJ700 Maxim ('85). I believe to be the 3rd owner (bought from broker). It's pretty clean with 26k miles on the clock. It might need some attention on the carbs as it wants to sputter and spit on idle. A few times it died on me just waiting for the traffic light to change. And on the way home from buying it, I was familiarizing myself on how hard I could brake/stop the bike and it will die when I pull in the clutch and apply the brakes really hard. So something is amiss.

Anyway, I had a question regarding the petcock. Not having a manual, I'm trying to understand what the settings mean. I'm confident RES is RESERVE, but what is the difference between PRI and ON? Should I be running on PRI?

Any advise welcome.

Thanks!

 

Welcome to the site, BC. Yes, there is a difference between On and Prime. Besides the fuel line, there is a vacuum line that runs to the petcock. In the On position, fuel will not flow to the carbs unless there is vacuum on the line, ie, the engine is running. In the Prime position, fuel will flow to the carbs without vacuum which would increase the chance of flooding the carbs if the floats and needles are not sealing properly. So, the bike should normally be run on the On position. If my bike sets for a long time (fuel evaporation), I will level the bike, set to Prime, start the bike, then return the petcock to On. This assumes everything is working normally. Many reported petcock problems on this web site.

 

Cole, that makes sense. Thanks for taking the time to reply.