Backfire, and wierd idle

[ApMx]

Im new to fourstrokes, my family has 6 two strokes and this is our first

Its an 05 yz450f

It backfires when I am say 3rd mid and shift down to second. It doesnt do it really besides then.

Also when you rev it, when it is decelerating it go to idle speed a little under choke for a sec then back to regular idle.

anyone can help ?

[Racer808]

Sounds like jetting, but I have been told you want some popping, not a lot but a few pops on decel is normal and wanted, so I have heard. No popping at all means to rich of jetting. But I get all sorts of opinions so who knows, I am still learning as well

[grayracer513]

Also when you rev it, when it is decelerating it go to idle speed a little under choke for a sec then back to regular idle.

Can you explain that a little better?