In some respects, an engine is similar to an air pump.  The air going in is combined with fuel, and then it has to go out.  When the bike comes for the factory the in/out flow is designed pretty equally, and on modern bikes both the intake and exhaust side are made to be pretty quiet.  The air box/filter/snorkel all work to keep the sound in and rain out....the muffler is designed to keep the loud portion of the sound in, and to dampen pressure waves that can decrease performance.

If you are not doing anything inside the engine to increase performance (bigger piston, higher compression, more cam, porting), then you aren't going to get very much gain by changing the muffler or air filter....or even the carb.  The cylinder head does not have a very good exhaust port design, the header is a bit restrictive...but it all works to make a decent running bike - youzguyz has proven the engine can go 140,000+ miles with normal maintenance.

There isn't much to be gained by taking out the paper element and putting in a foam or gauze filter.  Changing to a cone filter on the end of the carb most likely will runs worse than the stock air box and filter as they are generally very small and provide a turbulent flow that the CV carb finds confusing.  Removing the snorkel or drilling holes in the airbox....I remember seeing where someone took pressure/vacuum readings and couldn't detect any change....the snorkel helps to cut down on the intake sound and keep water out of the air box.

Changing to a DYNA muffler saves some pounds, looks better, sounds better....it is a worthwhile change even if the performance doesn't increase.  I don't believe the engine runs any cooler with a DYNA....the exhaust flows through both mufflers as fast as the engine spits it out, and I can't see how a little more or less pressure in the header changes the heat output of the engine.  At normal cruising speeds either muffler has plenty of flow ability, and how many of us can go at full throttle for more than half a minute?

Changing the stock carb to a round slide Mikuni on a stock engine won't increase the HP - it does change the response by allowing the engine to respond just a bit quicker to throttle changes.  It does however become far more sensitive to those with too heavy of throttle hands, and you need to learn to roll the throttle on/off and not "whack" the throttle open or closed.

If you do start to make internal engine changes for more performance (piston, cam, head porting), then changing the intake (carb, filter) and exhaust systems (header, muffler) becomes more necessary.

For a year I rode my bike with the stock paper air filter, stock carb, Wiseco 95mm piston, Stage 1 cam, stock header and a DYNA muffler.  It was a great running engine and had significantly more power than a stock engine.  It could still get 50-60 mpg depending on how I chose to ride....the only downside is the swiitch to Premium fuel.  Later I changed to a Mikuni Roundslide carb and although I don't know if the top speed increased any - the throttle was just a bit more responsive and the bike reacted just a smidge faster when you moved the throttle.

So.....it is my opinion that for most folks adding a DYNA muffler and making sure the carb jetting is correct is about all you need to do to a stock bike.  You don't need an expensive cotton gauze air filter, you don't need Kevlar clutch plates, you don't need a Mikuni (unless your stock CV carb is broken), and you will still have a very good running Savage.  Even a "highly" hopped up Savage engine is going to lose a drag race with any 400cc sport bike unless you keep the race very short.....like across the intersection!  

 

By the way, my exhaust pipe has turned dark blue near the engine. I remember reading here that it is from running too lean/hot.

Is the factory jetting around 14.7 A/F ratio, or is it significantly leaner? Is all the rejetting used to make the bike run richer than stoichiometric?

Yeah, but what about at sea level at room temperature and average humidity with regular non-ethanol gas? The question is this: is it set factory lean or factory stoichiometric under the typical test conditions like the factory or EPA would use? In other words, the "official" A/F specs? I typically ride somewhere around 1000 and 2000 feet elevation, so I shouldn't have as much of a problem as the lowlanders.

Also, how can one tell when they've hit stoichiometric? Is it the point where the engine runs the fastest under the least throttle (for idle mixture anyway), or is that slightly rich? Slightly lean? When it is said that more power can be gotten from a rich mixture, is that a consequence of less knocking, smoother power, and more torque, not higher speed with less throttle? Is high speed with less throttle a little lean? Does the most powerful mixture (rich) actually decrease engine speed a bit relative to throttle, but increase torque?
I've researched some of this before. I read that the idle mixture is supposed to be right with the highest vacuum (highest speed with least throttle). I've read some of the guides here on mixture tuning. I'm kinda asking for your opinion, or clarification on this.

As Serobot mentioned in his tuning guide, pulling the enrichment knob increases the engine speed. For me, 1 click will do it, and that is often enough to start the engine when its a little chilly. It's like the perfect setting or something, though I can't say about mileage or emissions. Furthermore, if I'm not careful, pushing the knob back in will very easily stall the engine at idle. I think it even runs faster when warm with this setting, although a good run during the heat of summer would better test that idea. I guess that means I should do the white spacer mod? I have been aware of this for a while, but reading it again today seems more clear. The article in the following thread seems to be the source for the idea that the carb is jetted very lean http://suzukisavage.com/cgi-bin/YaBB.pl?num=1104205157
Do you think the author of this article is correct?

But then, now that I look at it, it seems that the mods only give you back the power that the bike was supposed to have in the first place!
Its like Suzuki sold us the horsepower and the EPA stole it before it even left the factory  .

Wait a minute... No, that's still more hp than factory rated, isn't it?

I was referring to my own comments before I saw yours.


Also, a larger header pipe would give more buffer space for the gas to reside between pulses, important for a big single. But then, wouldn't a larger pipe increase back pressure according to Bernoulli's principle, or some such law. I gather that smaller pipes can actually reduce backpressure by increasing gas velocity, which, physics-wise, actually reduces pressure That all assumes no friction, I guess. I'm most certainly not a physics pro, in case I sound like it.  

Overthinking it, am I?

I'm like the Energizer Bunny of the Suzuki Savage forum: I just keep going--- and going--- and going