Here's some pics I promised. This is the first time I've welded plastic. I used a propane torch, which is not the optimal tool, but it can be done. My welds aren't as pretty as I would like, but the tank holds water. I will pressure test it before filling it with fuel.
To be brief, I tried and failed miserably at deforming the bottom of the stock CR250R tank. So I cut the bottom of the tank off, bought a 12x12" piece of 1/4" HDPE black plastic from Graingers, and welded on a new tank bottom. I cut the bottom bulge for the fuel spigot off of the original tank bottom and reinstalled it on the new bottom.
In these pictures, the engine is sitting in the new frame rails which are not yet welded together. The engine is probably sitting 3/4" higher than it will be when welded. The spark plug had plenty of room, and best of all, I believe I'll be able to run stock radiator hoses to an unmodified head. I haven't measured the tank's new capacity, but would guess it holds over a gallon--more than enough for a couple of 5 lap motos in the vet class. BTW, I know the spigot is on backwards in the pictures. It had to be that way when I was welding it.
I'm not too concerned about changing the center of gravity, because that all got changed anyway when I decided to put the 1/2 liter engine in.
![Image](https://bannedcr500riders.com/images/auto/8315eacffef0f384e41c1106a523aafc.jpg)