Drz petcock problem?

Hi guys, I'm having a fuel issue on my 400s, the bike starves for fuel on the "on" position and on "res" position on the petcock, but runs fine on the prime position?? I just installed an oversize clarke tank, and that is when this started happening, I have had the petcock out twice, made sure it's clean, but no luck? Could the new new tank be causing the problem (the petcock now sits below the carb, and the line has to travel up to the carb)?? The only line coming off the petcock is the main fuel line, no vaccuum lines at all. Any help would be greatly appreciated! Thanks

A vacuum operated petcock will not turn on without a vacuum hose. No wonder it is starved for fuel. You have to connect a vacuum line to operate the petcock.

Yeah, it sounds like you need to hookup the vacuum hose from the carb to the petcock. That was one thing I forgot when I did the clarke install and I couldn't figure out what was going on. I had to get a longer vacuum hose from auto part store and run the new one that was about twice as long. You might also want to check and make sure your fuel line from petcock to carb is not "kinked". I have heard of that reducing the fuel flow if the hose now takes a 90 degree bend to the carb. Hope that helps.

Thank you very much guys, that must be the problem, I do have a line running from the front of the carb, now basically going nowhere, it was simply too short to reach the petcock, so I never bothered with it. But, it was obviously the vacuum line, just now way too short because of the clarke tank, off the the auto parts store again!! Thanks again, my headache is now solved

There is a nipple on the carb for the vacuum hose. If it ran with no vacuum hose, the petcock is bad and does not actually shut off all the way. Dirty or defective or warn out.

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