Linhai 520 efi backfiring and won't start
 

I have a Linhai 520efi with 2 cylinders. when I start it backfires and won't start. but when I remove the coil cable from the lower cylinder the bike starts normally and when I put back the plug cable, it backfires. i have checked timing, it's okay. what could be the problem. thanks in advance

https://cimg9.ibsrv.net/gimg/atvconn...28c11db3a5.jpg

We've got the answer you seek on the ATV Connection homepage, here:

https://atvconnection.com/articles/a...ylinder-blues/