I bought this 1981 gs850g I´ve rode my Yamaha xj600 for5 or 6 years nonstop. Rain, cold, whatever. It got stolen so I came across this really good deal. The wiring was all messed up. I got it fixed enough g to ride it n it ran good for about a week then it sat for 3 weeks n now its like its sputtering n don´t want to take of it starts to die unless I poll the choke n then it will run until choke goes back in n it starts to sputter n then dies unless I pull choke back out n then it revs high n runs until choke goes back in . A friend said he thinks its an o2 sensor but it dontvsound like an o2 sensor to me. Any help?