A few things come to mind:
1. If it is your only source of fuel, your range will be severly limited due to less capacity.
2. Even with the limited capacity, the center of gravity will be affected rather negatively. You will be moving weight up and rearward. Not only that, you will be putting it behind the rear axle, which also removes weight from the front.
3. If you are ever involved in an incident where you and the bike part company at speed, the back of the bike is the second-most likely area to be damaged (right after the front end). There is NOTHING there to protect the tank or any tubing that leads from it to the engine. In the stock location, it is basically only vulnerable from above or the sides, but it has the handlebars to stop the bike from landing directly on the tank.
4. By raising the tank and increasing the vertical displacement between the tank and the carbs, you will be increasing the fuel pressure at the carbs. If your float valves are the least bit 'out of shape', you will know it rather quickly.
Many other points, I am sure, but these should be enough to make you think twice about it.
By the way, what is the meaning of "A (dollar sign) (dollar sign)".
It is rather suprising, but one of the words that our resident nanny filter does NOT filter out is ASS.
If you mean it, say it.
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