bobber xs400

So Im new to the xs world, but not new to Japanese bike world. I was looking for a 650 but hard to find one that isn't already butchered, so went with a 400. I'm sure I'll have some questions along the way which I'm hoping to have answered here :). So far I've stripped it down most of the way...

Hello all, have an 80 xs400 bobber ive built. Having trouble with it staying running after 10 15 miles of riding almost as if its ran out of gas, also will die sometimes when i kick it into gear from neutral. Any help would be amazing. Thanks!!