new exhaust back fire pop and flames

[killabeez450]

Newb to the forum in need of some help.

Purchased a bone stock 05 yfz 450.
Last night I installed a two bros full system running with an UNI intake open air box.

bike fires right up...actually better then how it did with the stock system.
when i blip the throttle it back fires and pops pretty often.
If I give it some real gas it will occasionally spit a flame out the muffler.
rode it up and down the street and it pops and back fires every time on decelration. Other then that the bike rides and feels okay.

I haven't had a chance to check the plug yet but if I do what do I look for?
any suggestions as to what the problem could be if any?
sorry for the newb question.

thanks in advance for the help.

[Bowtie]

Did you rejet it after you installed the pipe? What jets/needle are in it now and what altitude do you ride at? Google the area's altitude to find out if you don't know and then get back to us with that info and we can get you going in the right direction, but right now it sounds lean.

[leveldrummer]

yea, when ever you put on parts to add power, your going to have to rejet it.

[killabeez450]

ya I haven't done a rejet yet.. everything is stock settings on the carb.
others are telling me that it's lean as well.

some riding is at 3100 others closer to sea level.

thanks for the help

[leveldrummer]

Quote: Originally Posted by killabeez450

ya I haven't done a rejet yet.. everything is stock settings on the carb.
others are telling me that it's lean as well.

some riding is at 3100 others closer to sea level.

thanks for the help

the bikes are lean from the factory, and will swapping the pipe, you have made it even more lean, when you get the jets dialed in, you will be amazed at the power that pipe really added.