T5B ENGINE PROBLEM - RAN A HIGH SPEED FINE - SURGED AT IDLE

[Snowmobilingbear]

HELP PLEASE I AM PULLING MY HAIR OUT.

Here is what has happened. I tried to find a coil for my T5A motor - no luck. Some guy told me he had a T5A motor and sent it to me but it was a T5B motor. So - spark was good on it so I swapped carbs and got it to run. It would not idle - but would surge - but at full throttle it ran super - I was doing
wheelies haha. So with the surging I figured I had a carb problem. Took it apart and cleaned it ( I think pretty good but.. never know..) Put carb back on and tried to start engine. Guess what - now it wont run at full throttle or idle - it misses and you probably will not believe me but it backfires out the exhaust and then runs backwards better then it does forwards. I checked the
timming mark it was set a little forward so I backed it off to be before the timing mark in hopes of preventing the reverse running. I have not had it run in reverse but I still can not get it to run. When it does start the choke is on - I cleaned the fuel tanks value and removed the screen - due to blockage - fuel seems to flow fine now and float set properly. any ideas?