Whats wrong with the SV650 Tank? I have one and know them well. The petcock and pump are both vacume operated. One might have a bad diaphragm. The petcock can be checked with a vacume bleeder. The pump looks like a old style snowmobile pump. and is mounted to the frame near the airbox follow the lines you can't miss it. You might have just have a hole in one of the vacume lines, or it may have came unhoked.
Also gas these days has a lot of ethanol in it. Upto 10% its bad for metal and rubber parts and also clogs jets a lot faster. I have been draining my dirt bike tanks and carbs this year because the pilots have been cloging after about 2 weeks in the garage. Its easier just to drain the darn things.
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