04 ltz 440 backfiring

[jshea8961]

Hi I just got a 04 Suzuki ltz 400 with 440 big bore kit stage 2 hot cams and said to be jetted correctly but the bike backfires badly after I let let off the gas and has trouble idling with the choke completely off. Ive never owned a four stroke bike before so new to the whole thing. Could the jetting still be wrong? any advice is much appreciated!

[yfzgirl]

Did you actually consult with anyone about these mods before putting them on? Because when you start changing parts on the inside of the engine that's when you gotta do other changes that will cost you more $ so the engine can run right in all rpm's.The problem has to be in the jetting, it's probably not set right.1 more ? are you running stock or an upgraded jetting? cause if your running stock that's where your problem lies.Get back to me and let me know what's up.

[jshea8961]

Yea I wish I knew more about the work done but I was told by the previous owner that after he installed the 440 kit and full t4 exhaust he installed the proper jet kit obviously bigger jets to allow more fuel but it seems like it was running fine when he had it then the bike sat for a few months and now its backfiring at high rpms. I changed the engine oil, drained and added new gas and I ran it for a while thought maybe from sitting so long it just needed to run but nope the problem still persists. Could it maybe have to do with the idle mixture screw too lean? Thanks for your help!

[jshea8961]

Oh one more thing Ive always owned two stroke bikes and I know that they have a long rpm range when compared to a 4 stoke but it seems like this bike is revving out way to quick..maybe its just me haha

[yfzgirl]

You probably are running to lean because of the Jets. I don't think this guy is telling you the truth about what he did to the Ltz or even if it was running when he had it.I mean you gotta think why did he sell it, Prob.1-was it something he couldn't afford anymore? Or Prob.2-did he start messing around with the engine himself and didn't quite know what he was doing? That's my opinion.It sounds like you have too much air going into your carbs & jets and that can run you to lean.And you're right about 2 strokes they do revv quicker than 4 strokes but you can't compare them because their two different worlds all in all:D .I used to race a 1986 kawi KX125 and raced others (Honda) as well so I understand where your coming from,lol.