Question about Yamaha XS2 Motorcycles
By gas valve, you mean the fuel petcock? That should just unscrew right from the tank. However, you'd then need to weld in a new drain port at a low portion of the tank where you could re-attach it. It's a big, annoying job, as the current petcock location is designed to permit the maximum amount of gas to drain out of the tank. Plus, not every welder will agree to work on a gas tank, even if it's been boiled out to minimize the risk of residual gas vapor.
On the other hand, it's also possible that you don't have a correct tank for your motorcycle frame. In 1972, Yamaha sold an XS650, but not an XS650 Special. The "special" series didn't start until, if I remember correctly, 1979. So, it's possible that the original tank for your bike was replaced or upgraded at some point in its life. "Special" and standard XS650 tanks have noticeably different shapes. I have worked on a variety of XS650s, and I've never seen the fuel petcock physically touch the engine at any point, even when going over big bumps and chuckholes. Luckily, if this turns out to be the problem, XS650 tanks are relatively plentiful, for bikes of that vintage.
If you are pretty certain that you do have the correct tank for your year Yamaha, I would double-check the condition of the rubber mounting buttons on which the tank rests. These harden and crumble over time. Without the rubber shock-absorbing buttons, the tank is resting directly on the metal supports. This will lower the tank but a good .5-1.5" from where it should be resting. I can see how this could cause interference with the fuel petcock and the engine.
Good luck figuring out if there's an easier fix for your tank issue!
Posted on May 20, 2011
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Posted on Jan 02, 2017
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