Australia - I have a 2005 CRF 450X and have replaced the stock main jet (142) with a 165 as supplied by the dealers. The bike started 1st time and pulled very strong on a test ride. I noticed some backfiring on deceleration and when I shut it down, it didn't want to start again. Seems to be flooding. Any suggestions? The rest of the bike is standard, no mods at all. We are at sea level.