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Discussion Starter · #1 ·
So I am currently looking to buy this 08' z400. It has stage 2 jets and a pro circuit slip on and I am a noob to atv's so my friend came with to look at it etc cause he's more experienced and he said for having stage 2 jets and the slip on it feels like the bike is being restricted and want's to go faster but something won't let it. Is there any solution to that? is there a major problem or something?
 

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if thats all it has done to it, it is probably getting too much fuel. with just a slip on you shouldnt really have to rejet it. take the lid off the air box and see if that helps. depending on what the jetting is exactly you may have to go down a size or so.
 

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Discussion Starter · #3 ·
well the seller drilled holes into the lid and my friend said it felt alittle restricted and so he tried it without the lid and he said it felt alittle better but still some restriction
 

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The restriction is coming from the head pipe. If you take the stock header off and get a good aftermarket one it shouldn't feel restricted.
 

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^+1 Ya, all slip-on's do is make noise
 

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^+1 Ya, all slip-on's do is make noise
I hear this a lot. I have two 08 LTZ 400. Both 100% stock. A buddy and I raced the quads and it would just depend on who got the best start who would win the drag race. He weighs 5 lbs less then me. We would swap quads and the same results.



I then put a Yoshimura RS-2 slip on and a K&N air box lid and re-jetted the carb. This quad now wins every drag race no matter who rides it. It's not even close. So when I say not even close I mean 3-4 bike lengths.



So to me the three very simple things I did to the quad and relatively inexpensive $480 made a big difference.

Sorry I don't have any help for the OP problem but I just wanted to say my slip on does more then make noise
 

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Discussion Starter · #7 ·
yeah my friend told me to buy a K&N or a velocity stack and that it would make a difference. I'm gonna go with the K&N since I won't have money to spend for awhile and its cheaper.
 

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Yeah the k&n's are real good.. They will be the only filter I buy from now on. Get the outerwears cover for it. It will keep the filter from getting wet or dirty and hardly makes a difference in the amount of air flow.. The k&n is a cheap fix for the stock intake on the Z, sine the stock filter doesn't seal very well to the air box allowing leaks and unfiltered air to enter the engine
 

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I hear this a lot. I have two 08 LTZ 400. Both 100% stock. A buddy and I raced the quads and it would just depend on who got the best start who would win the drag race. He weighs 5 lbs less then me. We would swap quads and the same results.



I then put a Yoshimura RS-2 slip on and a K&N air box lid and re-jetted the carb. This quad now wins every drag race no matter who rides it. It's not even close. So when I say not even close I mean 3-4 bike lengths.



So to me the three very simple things I did to the quad and relatively inexpensive $480 made a big difference.

Sorry I don't have any help for the OP problem but I just wanted to say my slip on does more then make noise
Got a before and after dyno?

You're not going to notice any gains from a slip on, like I said before, your flow is only as good as the pipes smallest diameter(header).

If you can prove it with a dyno run, i'll stand corrected, but until then I call BS.

The airbox lid and your re-jet made the difference, not the slip on.
 

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Got a before and after dyno?

You're not going to notice any gains from a slip on, like I said before, your flow is only as good as the pipes smallest diameter(header).

If you can prove it with a dyno run, i'll stand corrected, but until then I call BS.

The airbox lid and your re-jet made the difference, not the slip on.
Biggie i'm not tryin to call BS on this here, but I got a question for you.. You said that the flow can only be as good as the pipes smallest diameter.. That is completely understandable. But when you say that slip-ons do nothing but make noise, wouldn't that be like saying that running without the slip-on part of the exhaust at all wouldn't do anything but make noise?

We can all admit here, the stock silencer is very choked up with it's multiple baffles and little passage ways.. After the exhaust gasses already pass through that skinny little crazy straw, it has to now be pushed through this big ugly can that has even more restrictions for flow.. This makes lots of back pressure, forcing the engine to work harder.. Now, if you were to put a more free flowing, straight silencer on there with a larger passage way for the exhaust gasses to flow, it would be a little easier for the engine to push those exhaust gasses out (nothing like what changing the header would do) but it would put just a little less pressure on the engine, making it more efficient and slightly increasing power.. (maybe not even an increase, but rather changing up the way power is delivered)

Think of it like this.. try blowing through one of those skinny little straw looking coffee stirrers (think of this as the stock head pipe).. now put your finger over the end of the straw and try blowing (much harder to blow out right? think of your finger over the straw as the stock silencer..) now try blowing out of that little straw without your finger there.. Much easier! Think of that as the aftermarket free flowing silencer.. now if you upgrade that little coffee stirrer (stock header) to a real straw (think of this as an aftermarket header), you'll find that it's much easier to blow out of it, but if you put you finger over it.. what happens? it's much harder to blow out.. either way the rear silencer has an effect on how the exhaust gasses can flow through.. with less restriction comes more efficiency, resulting in a change of the way power is delivered..
 

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You make a very good point i must say BUT i think for the money spend the extra and get a full system used, however you make a very strong point, and yes thanks for the awesome sig material
 

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Biggie i'm not tryin to call BS on this here, but I got a question for you.. You said that the flow can only be as good as the pipes smallest diameter.. That is completely understandable. But when you say that slip-ons do nothing but make noise, wouldn't that be like saying that running without the slip-on part of the exhaust at all wouldn't do anything but make noise?

We can all admit here, the stock silencer is very choked up with it's multiple baffles and little passage ways.. After the exhaust gasses already pass through that skinny little crazy straw, it has to now be pushed through this big ugly can that has even more restrictions for flow.. This makes lots of back pressure, forcing the engine to work harder.. Now, if you were to put a more free flowing, straight silencer on there with a larger passage way for the exhaust gasses to flow, it would be a little easier for the engine to push those exhaust gasses out (nothing like what changing the header would do) but it would put just a little less pressure on the engine, making it more efficient and slightly increasing power.. (maybe not even an increase, but rather changing up the way power is delivered)

Think of it like this.. try blowing through one of those skinny little straw looking coffee stirrers (think of this as the stock head pipe).. now put your finger over the end of the straw and try blowing (much harder to blow out right? think of your finger over the straw as the stock silencer..) now try blowing out of that little straw without your finger there.. Much easier! Think of that as the aftermarket free flowing silencer.. now if you upgrade that little coffee stirrer (stock header) to a real straw (think of this as an aftermarket header), you'll find that it's much easier to blow out of it, but if you put you finger over it.. what happens? it's much harder to blow out.. either way the rear silencer has an effect on how the exhaust gasses can flow through.. with less restriction comes more efficiency, resulting in a change of the way power is delivered..
im glad you took the time to explain, but your point is severly flawed. when you put your finger over the straw, you are plugging it completely! thats like saying you welded a cap on the end of your headpipe and tried to run it and then tried without it. no chit its gong to run better without being plugged. you are correct, slip ons will add MINUTE amount of power. that is why we say it adds nothing. you may get (if your lucky) .5-1 hp. that may be stretching it and until i see it on a dyno, i will say the same.

honestly i would say the say thing about just chaning the headpipe. i dont think that it would do much if anything only changing the head pipe with out the silencer. they need to work in conjunction to get the most out of it. believe what you want and if you want to waste your money on just a slip on, then by all means have at it
 

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changing from a stock silencer to aftermarket would be like going from blocking that straw 3/4 of the way to 1/5 of the way (aftermarket systems still have some blockage of exhaust flow, but not nearly the amount that a stock one has) And if it wasn't for the EPA and the rules that they make, Aftermarket exhausts and stock exhausts would be pretty much the same.. These machines would be as best performing as they could be, out of the box..
 

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I'm not trying to at all argue that full exhausts aren't the best route to go, because they are better than slip-ons by far! But I want to make it clear that slip-on's do more than just make extra unnecessary noise, that there is actually some kind of power change that comes with it, whether it be added power, or just a change in the way your current power is put out.. They allow the engine to breathe more efficiently and more freely. It would pretty much be the same argument as the 400ex intake boot that many of you guys have installed on your quads (I tried it too but I didn't like the way it seated).. It's a much larger boot and allows the engine to breathe much more easily.. Also it's pretty much just straight through, not meandering like the stock intake boot.. Because of this more smooth and free flowing air, the engine becomes more efficient, changing the power output
 

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Biggie i'm not tryin to call BS on this here, but I got a question for you.. You said that the flow can only be as good as the pipes smallest diameter.. That is completely understandable. But when you say that slip-ons do nothing but make noise, wouldn't that be like saying that running without the slip-on part of the exhaust at all wouldn't do anything but make noise?

We can all admit here, the stock silencer is very choked up with it's multiple baffles and little passage ways.. After the exhaust gasses already pass through that skinny little crazy straw, it has to now be pushed through this big ugly can that has even more restrictions for flow.. This makes lots of back pressure, forcing the engine to work harder.. Now, if you were to put a more free flowing, straight silencer on there with a larger passage way for the exhaust gasses to flow, it would be a little easier for the engine to push those exhaust gasses out (nothing like what changing the header would do) but it would put just a little less pressure on the engine, making it more efficient and slightly increasing power.. (maybe not even an increase, but rather changing up the way power is delivered)

Think of it like this.. try blowing through one of those skinny little straw looking coffee stirrers (think of this as the stock head pipe).. now put your finger over the end of the straw and try blowing (much harder to blow out right? think of your finger over the straw as the stock silencer..) now try blowing out of that little straw without your finger there.. Much easier! Think of that as the aftermarket free flowing silencer.. now if you upgrade that little coffee stirrer (stock header) to a real straw (think of this as an aftermarket header), you'll find that it's much easier to blow out of it, but if you put you finger over it.. what happens? it's much harder to blow out.. either way the rear silencer has an effect on how the exhaust gasses can flow through.. with less restriction comes more efficiency, resulting in a change of the way power is delivered..

I appreciate your attempt, but it doesn't work that way at all. I do understand how it can be easily confused, and I should have explained it in this manner earlier.

Any power change, as I mentioned earlier is negligible. You're not going to notice or feel it. It simply makes it louder. A slip on is a complete waste if you are looking to gain power out of your machine. If all you want is it to sound cool.. by all means. If you want power, you go with a full system.

There's only two pipes in this system, it's an extremely simple exhaust. If you did a flow test on both the stock exhaust, and the same head pipe with a slip on the numbers may be very different. The slip on may have much better flow. However it makes no difference if the same head pipe is used.

The exhaust system needs to be designed for the engine, it's not as simple as a stirring straw partially covered.

The power is in the head pipe. Exhaust systems operate on "Scavenging". The exhaust pulses that come from the engine need to be handled in an efficient manner. That's the head pipes job. If you've got a lousy head pipe (stock), your scavenging effect will not be very efficient, thus making the entire exhaust system (Stock muffler or slip on) inefficient.

If the scavenging effect is increased (aftermarket head pipe) then your entire exhaust will be more efficient, thus making more power.

Mufflers DO MATTER, but only when an efficient head pipe has become part of the system.

So, NO the slip on will not make any more power.
 
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