Do you have a '79 250 or a 1980? A 125 tank can be fitted to both, but it takes a bit of work to make it fit the '79 frame and a little more work to fit the 1980.
On a '79 frame there are 2 issues.
The fuel tap is on the wrong side, this is an easy fix if you can use a dremmel and a tig welder. Or know someone that can!
Secondly, the tank will sit a little low at the back and touch the pipe. I use one of those universal type tank rubbers that go round the frame tubes for old brit cafe racers. I cut it in half and then double it up on top of the original rear tank rubber. This raises it up off the pipe and makes it sit parallel to the pipe.
With a 1980 frame, you have the same 2 issues plus the front mounts.
You have 2 options here, drill new mounts into the frame and use the original tank mountings. Or cut the front mounts off the tank and fab up and weld new mounts onto the tank, so it will mounts onto the original 1980 mountings.
I have a 1980 with a '79 125 tank, it makes it feel really slim. I run 43mm forks with big billet yokes and have no clearence issues with the forks touching the tank. And unless your going to be doing 40min plus races or desert racing then it holds more than enough fuel.
Stevie
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