This is too late for you now, but when you put those new stickers on make sure that there is no dirt and oil(evaporated Pre-mix !!) on the plastics-tank esp. Once they start to peel dirt gets on the sticky stuff and it is game over. I have seen people try things with not much success. Thing is that you shouldn't use anything that "melts" the plastic like superglue etc. Try the type that you need to put on both pieces and let dry before pressing the two together.
Unfortunately I have never had any success doing this.
Just rip off the old stuff and slap on some fresh grafix and while you are at it shiny new plastic-always nice to have a fresh looking bike!!
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