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Tank tunnel widening technique

7083 Views 23 Replies 11 Participants Last post by  mattsway
Hi. I have a CB200 tank to go on my XBR500 build and need to get clearance where my frame rails attach to my top tube. At this location, the tank tunnel is 130mm and if possible needs to become 160mm. Having googled around, I hope to be able to use a plastic mallet. Any advice on weight/shape of mallet and technique - do I strike against the inside face of the tunnel first, or the bottom edge where the wall and bottom of the tank meet? Any prep to help move the metal most effectively? I thought about filling with boiling water, but I could always purge the tank of petrol/gas fumes and use a butane torch. Many thanks.

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why on earth would you trade that great looking xbr500 tank for a useless cb200 tank?

Old honda tanks are thicker metal than later tanks. They are also crimped seams. For the most part working slowly and tapping more than tapping harder is the way to go, the last thing you want is the metal to pull because you are hitting it and then the seam at the bottom splits.

But back to this partially uselsess and ugly mod for a second - have you ever seen a GB500?

Land vehicle Motorcycle Vehicle Car Motor vehicle


This uses almost the same design tank as what you have and it is proof that you can have a pretty, functional, and retro design using something as "modern" as your tank.
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