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Differences are minimal, but you're probably better off with the right header, especially as there probably are more slip on exhaust options for the SP2.
 

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I was told that the sp1 is round exhaust and the sp2 is more oval. And one exhaust works for all years but not the other.
I'm in the same dilemma.....I have an sp1 an trying to nail down a full system or even slip-ons for that matter,and I'm finding near impossible.
 

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The SP1 has round exhaust ports while the SP2 has D-shaped exhaust ports.
The headers on SP2 are also D-shaped and won't work on SP1s.

Here's a comparison
 

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Thanks.
Looks like the outside diameter is the same? and the inside is D shaped. Why would Honda do this. Do you know of anyone that has tried to fit and after market exhaust for an 2002-2006 on a sp1?
 

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so, i had bought an sp1 header to try on my sp2, no dice. The SP1's header has a shorter front pipe, you know from where it attaches to the head to the Y in the pipe. I already bought an SP2 header, so now I have a spare SP1 header.
 

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Looks like the outside diameter is the same? and the inside is D shaped. Why would Honda do this. Do you know of anyone that has tried to fit and after market exhaust for an 2002-2006 on a sp1?
They made the exhaust port D-shaped for improved exhaust gas flow.
This is done a lot on performance engine.
Some even have D-shaped intake runners for the same reason, although you don't see it as often on bikes as they try to make the intake runners as straight as possible.
Gas flow is slower at the inside radius, so by pinching the shorter radius into a "D" shape, it increases overall flow velocity around the curve.
 

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so, i had bought an sp1 header to try on my sp2, no dice. The SP1's header has a shorter front pipe, you know from where it attaches to the head to the Y in the pipe. I already bought an SP2 header, so now I have a spare SP1 header.
I'm not sure what happened there, but you can for sure mount a complete SP1 header on a SP2 motorcycle. Stock SP1 header + SP1 slipons will most likely mount up just fine on a SP2. This applies to aftermarket full systems, like the Jardine 2:1 as well. (Both my SP2s use SP1 systems...)

The only thing you absolutely cannot do is mount SP2 slipons to a SP1 header, or vice versa. The slipons have to match the header.
 
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