brute back firing

swabber30 · April 9th, 2010, 01:00 AM

ok guys i have a 07 750 brute and i put a pro curciut pipe on it and now i'm starting to get a lot of back firing from it to the point that i shoot flames about a foot out of the tail pipe. so i was wondering maybe i'm to rich or is the pipe doing it. would it help if i put the stock pipe on or should i change the jetting. i have dynatek cdi and twin air power flow filter and have 142/145 jets in it with a mud lid. so if you have any ideas let me know thanks.

NMKAWIERIDER · April 9th, 2010, 09:42 AM

Quote:

Originally Posted by swabber30

ok guys i have a 07 750 brute and i put a pro curciut pipe on it and now i'm starting to get a lot of back firing from it to the point that i shoot flames about a foot out of the tail pipe. so i was wondering maybe i'm to rich or is the pipe doing it. would it help if i put the stock pipe on or should i change the jetting. i have dynatek cdi and twin air power flow filter and have 142/145 jets in it with a mud lid. so if you have any ideas let me know thanks.

Usualy...when you reduce the restriction in the exhaust, the charge volumn increases and without changing the jets, it goes lean. This is one cause for poping in the exhause as unburned hydrocarbons and detinated. Try duct-taping about a third of the opening of the mudlid and see if it quits. That might be a bit much and it might be a little rich, but it will tell you if rejetting richer will do it. You might also give the A/F screws another 1/4 turn open.

Are those jet numbers you mentioned DJ numbers or Kiehin's. If they are Kiehin's and you are below 3900 feet, you are way too lean even without all the extras.

gusmx5 · April 9th, 2010, 12:24 PM

In general from what i know,all the v engines backfire when you put a more free exaust.Especially the carbed ones.I saw one day a honda VFR wearing akrapovich exausts shooting flames when he left the throttle!!!!It was like he had a machine gun in his exausts.My friends' 06 brute backfired from the day he bought it...his exaust is more free than the oem one due to the customizing they do in KL italy to make them street legal for greece...