Gabriel at Zen Overland has made these brackets up, to fit an Acerbis Tank to the blue plastic tank bikes only, metal tank ones to follow soon.
Here is what he say's
Zen mounting kit, allowing the Acerbis XR tank to be fitted to a TTR250.
We're pretty sure you can use this mounting kit to fit most of the Honda XR Acerbis tanks to your TTR (the actual plastic tank seems to be the same for the Honda XR range of bikes, but Acerbis supply different mounting kits depending on whether it's sold to an XR250/XR400/XR650L customer).
Please note the Honda XR650R tank is completely different, and this fitting kit will not work with that tank.
The tank we used when designing and refining these mounting parts, was one bought for a Honda XR650L (22L capacity, in white). So we recommend that you buy this tank when using our TTR mounting kit.
The Acerbis part number for this tank is 0001590.030
Fuel Tanks on order! And will be in the shop soon :-)