Stock Valk pipes ?

[98pacecar]

After reading, twice,,,,,,,,,,,,, (in da 6 inta 6 thread)

dat the OEM  header pipes are,,, double walled,, I need ta ask ARE they,,,,, errrr not?   

I figured they were, n' recently, said so to another valk owner,,, who told me they, were,,,,, NOT....... 

Soooo, which,,,,, IS IT ??    ???

Double,,, errr,,,, single ??     

[John Schmidt]

Yes, that's the main reason they don't blue/turn color unless you really cook them because your carbs are out of whack....or you idle it too long.

[98pacecar]

Ok since no one has offered, a,,,,,,,,,,, rebuttal...   

Thank you John, fer confirming,,,,,,,,, my belief...   

[wiggydotcom]

I'll second what John said.. 

[98pacecar]

 2      zip     

fer,,, double wall.........       

[Ricky-D]

A look inside the receiving end of the exhaust pipes will reveal the reduced diameter of the inner pipe. They are about the same diameter as the piggies at the end of the muffler.

***

[MarkT]

They are about the same diameter as the piggies at the end of the muffler.

***

ID of the header inside tube mics at 22.45mm.  ID of the piggies mics at 19.50mm.  So the area of the headers is 395.84mm² while the exhaust is 298.65mm².  So the headers are 32.54% larger in area and potential volume of gas passed.

[pancho]

They are about the same diameter as the piggies at the end of the muffler.

***

ID of the header inside tube mics at 22.45mm.  ID of the piggies mics at 19.50mm.  So the area of the headers is 395.84mm² while the exhaust is 298.65mm².  So the headers are 32.54% larger in area and potential volume of gas passed.

Well, your math is correct, so if your measurements are correct... that would mean more pressure at the end of the exhaust system, hence, some backpressure as the same amount of gas must be passing at both ends  (HA..think about that!!)  I wonder if that is why stock pipes deliver more HP than straight pipes like cobras?? It is probably a bit more complicated than that, but that may be part of the equation.

[F6Dave]

I remember when I bought my new BMW airhead with OEM chrome single wall pipes.  They looked so pretty at the dealership, but by the time I got it home they were already blue.

[BlueValk]

Just a thought about the difference in diameters.  The exhaust temp may be considerably cooler by the time the piggies are hit, so would have less pressure, and need less diameter.

I know I have put my hand pretty close to the end of exhausts in the past without a problem (hot and damp, but not burning).  I probably could not do that right at the end of the headers.

Just my .02.

[pancho]

Just a thought about the difference in diameters.  The exhaust temp may be considerably cooler by the time the piggies are hit, so would have less pressure, and need less diameter.

I know I have put my hand pretty close to the end of exhausts in the past without a problem (hot and damp, but not burning).  I probably could not do that right at the end of the headers.

Just my .02.

Yeah, thats a valid point.

[8Track]

So if your piggies have been cut off, has there been a loss of horsepower? Mine have been cut by a PO.

[donaldcc]

   So I had cobras when I first got bike and about a year later I bought some OEM pipes off e-bay and changed them.  the headers are blue and gold so I guess they were really heated up???

 i also have another set of OEMs with about 200 miles on them I got off craigslist for $220-250 (can't remember) from a lady whose father took them off right after getting bike 14 years ago and she wanted them out of the garage.  they are pristine

 so the ones I have on bike had too rich fuel or sat there forever with bike running???