running lean issue

[5speed]

86 fj1200..stock engine.
I added black widow pipes and these mufflers due to their claim I wouldn't need to rejet my carbs.
https://delkevic.com/yamaha-fj1100-fj1200-1tx-84-88-slip-on-13-5-x-oval-stainless-exhaust-muffler-kit/
well..when I let up on the gas it back fires out the exhaust..
so my questions are..does anyone else run these mufflers and did you have to reject the carbs?
I plan on removing the baffles because it sounds like a Ducati now..or a 2 cylinder john deer tractor. lol
OH..if you order pipes from  Black Widow you're possibly going to have to mod the end that goes in the engine. They make it to long and you can't put the chin spoiler on unless you shorten the pipe.
I e-mailed them regarding this and they claim their pipes are correct. lol ya..ok.

[MarioR]

86 fj1200..stock engine.
I added black widow pipes and these mufflers due to their claim I wouldn't need to rejet my carbs.
https://delkevic.com/yamaha-fj1100-fj1200-1tx-84-88-slip-on-13-5-x-oval-stainless-exhaust-muffler-kit/
well..when I let up on the gas it back fires out the exhaust..
so my questions are..does anyone else run these mufflers and did you have to reject the carbs?
I plan on removing the baffles because it sounds like a Ducati now..or a 2 cylinder john deer tractor. lol
OH..if you order pipes from  Black Widow you're possibly going to have to mod the end that goes in the engine. They make it to long and you can't put the chin spoiler on unless you shorten the pipe.
I e-mailed them regarding this and they claim their pipes are correct. lol ya..ok.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html