96_banshee_96 Posted September 13, 2008 Report Share Posted September 13, 2008 Ok guys I know this is a banshee forum but I know people have YFZ 450's too and I need some jetting help. I just picked up this 04 YFZ 450 a couple weeks ago. It backfires in mid 2nd and 3rd gear. Also backfires on down shifts. It also shoots blue flames out the exhaust sometimes when back fireing. little poofs of black smoke comes out the exhaust when I blip the throtle in neutral before its warm but after its warm no smoke. Im from michigan I believe elevation is around 500- 800ft round here. What jets should I be runing or start with? what needle position? How do I solve this problem? Mods are: Cam mod. Dont know if it was realy done guy told me it was but who knows. HMF slip on pipe K&N air filter lid removed from box NCVQ needle Quick shot 2 Fuel screw Quote Link to comment Share on other sites More sharing options...
YFZ350kid Posted September 14, 2008 Report Share Posted September 14, 2008 if your backfiring on decel and when you let off the throttle to shift then check the pilot jet, good chance you need to go up a size or 2. for the popping down low when its cold, let it warm up first... from my past experience with an 05 yfz that i used to have, the cam mod made the bottom seem lacking and sluggish, but it let the motor breathe better up high in the revs making it feel a bit more like a 2 stroke. my 05 used to backfire on decel once in a while, but it was never an issue. but if it does it constantly as i said before, bump up you pilot jet. Quote Link to comment Share on other sites More sharing options...
gumby6t9 Posted September 14, 2008 Report Share Posted September 14, 2008 How many turns out is your fuel screw? If you have the adjustment turn it out another 1/2 to 1 turn. If not bump up the pilot size. Quote Link to comment Share on other sites More sharing options...
Quadatic20 Posted September 15, 2008 Report Share Posted September 15, 2008 (edited) My 07 YFZ450 set up... HMF Sport Series Slip-on UNI-Foam Air Filter Cam MOD Main: 170 Pilot: 45 4th Clip on NCVQ 2 1/2 turns out on air/fuel screw No airbox lid ~~~CLICK HERE FOR JETTING FOR ALL PIPES AND SET-UPS~~~ Edited September 15, 2008 by Quadatic20 Quote Link to comment Share on other sites More sharing options...
96_banshee_96 Posted September 20, 2008 Author Report Share Posted September 20, 2008 I changed the plug. There is already a 170 main and 48 pilot. Still doing the same thing. What should I do now Quote Link to comment Share on other sites More sharing options...
Bill Posted September 20, 2008 Report Share Posted September 20, 2008 My brother has A yfz450 and he was having A similar problem. What the the problem ended up being was the valves were out of adjustment. In the owners manual it says that the valves should be checked for clearence every 25 to 30 hours of use.And the valve pads should be changed as well.Just A thought, good luck. Quote Link to comment Share on other sites More sharing options...
96_banshee_96 Posted September 21, 2008 Author Report Share Posted September 21, 2008 My brother has A yfz450 and he was having A similar problem.What the the problem ended up being was the valves were out of adjustment. In the owners manual it says that the valves should be checked for clearence every 25 to 30 hours of use.And the valve pads should be changed as well.Just A thought, good luck. Did he adjust them himself If so how hard is it to do? If not how much do you thing it would cost for the stealership to do it? Quote Link to comment Share on other sites More sharing options...
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