That is a after market tank I think, at 4gal. I don't think it will work. You need a XR 100- 250 stock tank. I got mine on e-bay for $50. Also I can't see the mounts on that tank. Make sure you get the rubber mounts and petcock as they are another cost. IMO I'd keep looking. Here's one on e-bay now that looks good.
 
http://www.ebay.com/itm/Gas-Fuel-Petrol-Tank-Red-86-1987-87-Honda-XR250-XR-250-250R-XR250R-/111277990329?hash=item19e8af61b9&vxp=mtr#ht_87wt_848
DSCN1960.jpg 

Craig
Joshua Tree, CA

  
Last Edited By: tuna Feb 12 14 7:32 AM. Edited 2 times.