I have been asked a lot of questions about the oversize tanks since I mentioned them in other threads. So, I figured I would do a quick write up and update on my experiences with them. I first purchased the Acerbis tank as it was cheaper. I didn't realize it at the time, but the gas cap ended up being right where the pop-off seat is on the stock setup. That would mean the cap and vent tube would likely get sat on when you slide forward for the corners. I decided to send it back without even mounting it (or taking any pictures) so I could get a full refund. I immediately ordered the IMS tank because it still uses the stock seat configuration. The tank looked nice, though it was kind of a pain to mount. I have additional wires for my headlight that follow the fuel line route which complicated matters slightly. Future tear downs will also be a little more difficult, but once you figure out a good order for R&R, it goes pretty quickly. When I installed the tank, I did not disconnect any wires or the fuel line from the fuel pump. A quick tip is to use silicone spray on the rubber grommet attached to the sub frame (they are to protect the tank from chafing.) This helps the tank slide up into the sub frame more easily. I had not ridden the bike, short of breaking it in, so I cannot comment on how its' addition may have effected handling. Though, I do have the light front end feeling I am trying to get rid of. The tank generally fit well and I did manage about 70 miles on it while trail riding 2 track and graded roads. A couple weeks after I mounted it, I noticed a rather strong gas smell around the bike. A quick peep under the tank and I could see that the fuel pump to tank seal was leaking. I figured it was likely leaking because I didn't replace the O-ring, as the manual recommends. While I was waiting for the O-ring to show up in the mail, I did a little research and found this: http://www.chronicmx.com/ims-2-4-gallon-oversized-fuel-tank-the-ultimate-sleek-solution-to-todays-tiny-motocross-gas-tanks/ The above link talks about the casting flaws that can cause leaks. When I inspected the fuel pump opening on the bottom of the tank, I saw so rather large curved grooves around the opening that were definitely from the factory. I sanded them down as best I could. When I compared the stock tank to the IMS tanks, the stocker had a more definite sharp edge around the opening for the O-ring to seat against. The IMS tank was nowhere near as well manufactured (or designed) as the original. I also noticed a visible groove in the original O-ring from where the tank seated on it. That made me hopeful that the sanding and new seal would remedy my problem. Well, it wasn't enough. After I got everything back together and filled her up to the brim with fuel, everything looked good. That was at midnight as I was going riding the next day. In the morning, I checked the fuel pump and the bastard was all wet, yet again. So instead of riding that day, I tore it back down. I did some more sanding and added a very small amount of aviation quality fuel resistant liquid gasket to the area where the swirl marks were. I hoped that filling them in a bit would help. The fix seems to be holding up now. In the end, I like the IMS tank, but wish more effort was put into the design and maunfacting of the critical fuel pump to tank mating surface. It is really frustrating when you spend good money to buy performance parts for a bike and they end up being of lesser quality than stock. The pictures below are of the installed IMS tank.