Welcome to the site !!
First I would like to mention that you would get more replies if you posted this in the 250R part of the forum , or the General part of the forum . rather than "Land Use Issues"....Maybe Ken can move it if he pops in .... with that said ........
What you did not mention was Fuel Pump , or Injector , or Stator .... these would be 3 things I would certainly look into as far as if they are within spec .... I am assuming you have a manual ... to do any serious electrical testing you will need the Factory Service Manual , as the Owners Manual will not cover as much detail , or much of anything about the stator or any electrical tests ............ , also , if it sat for a long period of time while rebuilding (say 3 months or more , as you did not mention if it sat or not) most likely the gas is bad as well .... and you need to completely drain the tank ..... and start with FRESH gas , not more gas from your can that sat for months , but new from the gas station gas ... it makes a huge difference , try to run Premium if possible , at the very least run non ethanol ...
One last and important thing , have you noted any codes when first starting ??? , the map switch will flash whatever map you are on , then go out , it should flash 1 or 2 or 3 three times , then stay off , if it flashes more , like , if it flashes a few times , then pauses then flashes again , you need to count the flashes (say it flashes 1 time then a slight pause , then 3 times ... then a longer pause , then 1 time , then 3 times , this would be code 13 for example) , so you need to look in the manual and see what code 13 is (example)