EXUP Worldwide

Alright, I through a bolt-on onto my YZF. It backfires a bit when I let off the throttle. It's runnin' screaming fast, and haven't noticed any down side other than the slight backfire.

Is this anything I should worry about?

I've always heard "lean equals fast". Is this true? That's how it feels, fast.

Also, there's a bit of odor from the pipe after it's all nice and hot. I've only ridden it a couple times since a put the pipe on. Do new exhausts have some type of coating on them that burns off? I just did the clutch and want to make sure that isn't what I'm smelling.

Everytime I do something to the bike I'm a bit panic-stricken until I'm assured all is well. I have no faith in my mechanical skills.

I assume what you're saying is that you put on an aftermarket slip on muffler?

If that is what you did, it would create a lean running condition unless you compensate with bigger jets in the carbs. With stock airbox you should go with a Stage 1 jet kit. Factory pro is the way to go.

As for the backfiring, check for leaks in the exhaust system. Particularly where you bolted on the slipon. A leak can cause a popping sound when you let off the throttle.

I'm confused. I'm assuming it's running lean because of the popping I hear. If that's correct I'd have no reason to think the exhaust is leaking, right? Or are you thinking the popping could be caused by both?

I bought the bolt-on (slip-on) because I understood no rejetting would be required. I thought that was only necessary for full systems.

you don't need to rejet if you change cans.
it may be a tad lean on decel...look at the plugs. They will tell all.
You MAY ....need to turn the pilot airs out an eighth turn.

I stand corrected... Jim knows his stuff

Although that is what happened with my FJ. The previous owner put on Cobra F1 slipons, and it started running real hot. (melted the lower cowl, next to the stock exhaust header) He took it to a shop, and they put in a stage 1 jet kit, no more problems. I also had this problem with my FZR1000, but that had a full system.

Thanks for the help, guys. I'm going for a long ride tomorrow. After that I'll decide whether to adjust the air screws.

I'm still curious though: has anyone encountered the pipe smell I'm talking about? Some kind of factory protectant or something that burns off?

Does lean equal fast? More power?

Does lean equal fast? More power?

Strochiometric is 14.something to one....max power will come somewhere in the neighborhood of 12.5:1 That would be richer...so, no....lean from strochiometric will get you holed pistons....
But I'll bet you a dollar that you are not even close to strochiometric

I barely have a rudimentary understanding of what you're saying, Jim, but I'll take your word for it because you are THE MAN!

(it's the ratio of air to fuel, correct?)

Yea it's fuel air.With all fuels, there is a ratio at which all of the fuel and o2 will be consumed. With gasoline it's 14 point what ever...I don't remember exactly...
That is not where max power comes...it's a bit rich from there.
Leaner gets you more heat and no cooling effect as the fuel air charge cools the motor. This leads to effectively too much advance as cyl pressure rises, causes more heat and detonation . Results...holed pistons

LoveToRide wrote:I'm still curious though: has anyone encountered the pipe smell I'm talking about? Some kind of factory protectant or something that burns off?

My D&D slip-on stank for almost a year. Everytime I parked it after coming home from a ride, I'd shut it down and start taking off my gear and be like "Why does that smell?" It doesn't smell any more.

That's good to know. It's the first time I've ever had a brand new pipe on any bike I've ever owned.