I have a 2010 kx250s that the engine locked up on, I bought a wrecked 2018 (fuel injected klx250s) and put the engine on mine.. I used everything from 2010 except engine/trans, but now it will not run except while starter button is held down and instantly stops as soon as it is released. I have swapped out everything externally that I had and even put my stator in the new engine. I have unplugged and replugged all connections. Any guidance would be greatly appreciated, The 2018 had no tank or i would use the 2018 wiring and make my 2010 fuel injected but not an option yet and just want to get it running with the carb setup.