Modify bottom of gas tank for clearance..

[i_mangle_sht]

I need about 1" of clearance on the bottom of the gas tank for cylinder head and carb. clearance, any recommendations on how to do this without destroying my new IMS tank?

[racerx573]

Is it a 250R chassis? I used aluminum spacers on the lower tank mounts on my 250R. We took off the petcock and cut the lower fuel line spiggot off and welded it shut, to allow a little more clearance, and we only run it on reserve. Just get some spacers of some kind and use longer bolts, and some rubber blocks in between the frame/tank.

[i_mangle_sht]

are there any body plastic fitting problems

[440challenger]

is this a 400ex with a trx 450 or crf 450 motor in it??

[i_mangle_sht]

400ex with a xr650r motor

[racerx573]

Hmmm.. a 400EX may be a problem then. Simply because of how the front plastic runs up over the tank and the tank cover, unless you trim that so it will fit flush against the tank.

[Caseys 300ex]

You could heat up your tank and push up with a spoon a little at a time. Dont push up all at once ur you can put a hole into the tank.

[malibuj]

I've been mocking things up for the same conversion. I didn't think there would be a problem spacing the tank up 3/4-1". The fender brackets can be modified/lengthened/re-fabbed to allow the tank movement upwards. How about some pics?

[brian350rx]

On the old 350rx conversions we ran into this problem. Cover your carb or whatever is in the way with cardbaord or a piece of rubber (something that is smooth and wont pole a hole in it), heat the tank with a heat gun and actually put it on and "smash"it in place. If you need to then you can get minor adjustments with spacers.
Good luck!

[i_mangle_sht]

thanks for the advice, i should have some pictures up here in the next few weeks. Id like to post them with the motor,tank and radiator installed instead of just 1/2 the motor.

[Desert650ex]

Hey there. I was just surfing around and found this site. I have 2 650ex's that are built for desert racing. They are both in 400ex frames. One of the biggest problems i have is the fuel tank! Are you using the top 650r head mount and mount on the 400 frame? Are you using a IMS tank for the 400ex and is it a desert tank or stock capacity? I might be of some help. After racing this things for a couple years i think i have the bugs worked out.

[i_mangle_sht]

yeah im using an ims 4.3 gallon and yes im using the head mount.

[Desert650ex]

What i had to do was this: The tank just kinda sits on that upper head mount and rocks back and forth. It doesn't sit flush with the frame. So i use the mounts on the front of the tank and the stock mounting holes on the frame to snug the front of the tank down. Then i use a hose clamp around the frame and through the side mount on the tank to really tighten it down. I am going to weld some kind of mount on the frame to attach the tank to but have never got around to it. It might not be the cleanest way but it holds the tank secure ( even after 500 miles of racing ). I also had to add 1/4" spacers on top of the frame mount so the tank would set a little higher in the front so my GPR stabilizer would not hit the front of the tank. It all works pretty good. I don't know if this helps or just confuses things. By the way the two 650's i have are for sale.