pipes

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As a general rule, a 4-1 exhaust system on a bike will weigh a few pounds less and have slightly better top end than the stock 4 into 2 exhaust system. Our stock exhaust headers are double-walled, while the replacement 4-1s use single-wall.

A stock 4-2 exhaust system generally will be quieter, weigh a bit more, and have better mid-range/low-end than a 4-1. The stock pipes, at least in the case of my bike, will also have better ground clearance both below the bikes' center and when cornering. The two individual mufflers are each smaller than that of the 4-1s, and the factory does a pretty good job of tucking them in out of harms' way.

Most 4-1 pipes will feel faster: they almost always have a big dip in the torque curve that makes you feel the hit when the revs crawl further up in the powerband and get out of the soggy zone.

If you only change the pipe, all you'll accomplish is to move the engines' torque peak further up the powerband. It will probably make a bit more torque at higher revs (More HP! ) at the expense of your mid-range.
Proper rejetting will help, but can't banish this new-found big soggy spot in the torque curve.

 

I have the 4 into 1 Mac system on mine and It was there when I bought the bike, so I can't say if it made any difference in the performance or not. It does not have the heat shields on, like the stock system has, but mine hasn't blued. I've ridden the bike for 7 years and the Mac system sounds good and has a baffle that's removable, so you can re-pack the fiberglass when it starts getting louder.

 

One additional note; when changing to a 4-1 the carbs have to be rejetted. Most 4-1 setups call for an increase of 2 jet sizes. Just want you to know that it is not unbolt stock system bolt on 4-1.

 

I have not rejetted my carbs with the Mac exhaust on (still have main jets and needles) Just adjusted the air screws so far and it runs like a raped ape.