Mex 190 gas
Not wanting to seem like a nit picker Mike but your warning about feul scarcity along Mex 190 is a bit misleading. There is actually a good supply of PEMEX stations in all the larger towns so that from Puebla to Oaxaca one can hit one of them just about every 60km to 70km. South of Oaxaca they may be spaced a bit farther apart , and even then the small towns without PEMEX have a private source if you are really desperate. Also on the mountain route Mex 200 from Tapanatepec -Tuxtla Gutierrez -Comitan to Guatemala border gas is plentiful. So ,any bike with any reasonable size gas tank should have no problem. Mind you , if you like dodging into a lot of side roads to explore you can rack up a lot of kilometers between PEMEX stations. But there is no need for concern.
As to road condition , this too has all been well taken care of since Stan . This past I winter rode through the area Mex 200 Tehuantepec to Tapachula and all was in good shape, washouts rebuilt, no delays, even on the sinuous Mex 211 from Huixtla up into the mountains where complete new sections were just being given the final paving layer.
Great roads , great scenery. Enjoy.