My bike wont stay running

Sounds like a choke issue. but I am no expert on Bikes.

follow the cable from the start to finish it might have been bent or damaged. then have a look at the carbs they might have been damaged in the two accidents if the mix is wrong or they are letting in air

could be you spark plugs need replacing

was fuel left in the carburetors when you parked it your metering jets might be slightly clogged with varnish i dont recomend opening them yourself take it to a professional and next time you park it for an extended period of time close the fuel valve and leave the bike running until the carbs run out of gas "the bike will stop running when this happens"

first drain the carby, then set your air mixture screw 2 turns out, from the fully turned in position. The starting proceedure is as follows, when the engine is COLD, turn on fuel, pull on the choke fully, and kick the engine over. DO NOT use any throttle, when the engine is cold, and the choke is on. Remember Choke on, NO throttle.
When warm, no choke, and a little throttle when kicking.

your BMW75 has a cold start sensor fitted to its fule system the choke leaver dose nothing but raze the reves a little its not a choke,,,thats withing the fule system if the sensor is not working right it wont tell the fule pump to enrich the fule mix and it will be hard to start from cold,,also if you start the bike up you must run it till its hot or the choke will stay on and flood up the engine the next time you try to start up
the choke sensor is in the water jaket, try changing this part first

check condition of air cleaner filter.

Carb needs to be removed and thouroughly cleaned.

When starting any engine, run engine until it will idle without the choke on, then ride.

Check fuel pressure. Pump may have crapped out. If pressure is good, clean and rebuild carb.