I am having a problem with backfiring - any suggestions? Occurs when deaccelerating and/or downshifting. Want to avoid the expense of having the carborator torn apart if there is a simple fix. Is not the spark plug as the bike starts easily for me. Noticed that one time I left the choke on accidentally and it didn´t backfire for me at all, but don´t want to ride with choke on all the time. Any suggestions would be greatly appreciated.