I ran the Cycra 2.9 tank on my 98 YZ125 and could not make a 2 hour race on it. I ran out on the last lap at a Mid-South while leading 200A:eek: . Plus I had problems with the gas cap, it would not come off, you would have to use a pliers sometimes to get it off. Cycra said it was a problem on some if the early tanks. Cycra did fix this and sent me a new one, but I was without a tank for a couple of races. With the Cycra tank you can not run radiator guards (the Works Connection ones) so that is something to think about too. I finally switched to to the Clarke and could make the full two hours, just that extra .2 helped out, I would be very low but never ran out. Plus I could run the radiator guards with the Clarke tanks. I ran the Clarke tank on all my Yamahas unitl I switched to KTMs.
A friend ran the IMS tank and on the 125 he had to indent the tank where the pipe was so that the pipe didn't hit the tank. It still didn't fit very well on the 125 and I wouldn't recommend it for the 125, plus as other people said it only used one bolt to hold the tank on, and you also could not run raditor guards (works connection) with the IMS tank.
So my vote is find a Clarke.