Question on pipe diameter

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Jun 9, 2010 | 08:21 PM

2006FLST

Thread Starter

Road Master

Joined: May 2009

Posts: 1,232

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From: Powder Springs, GA

Question on pipe diameter

Aside from a sound difference, what is the difference in running 2in versus 1 3/4in pipes? You don't see them on bikes that much anymore but I love how the smaller diameter pipes sound. Does the smaller diameter provide more back pressure?

Jun 9, 2010 | 10:43 PM

oct1949

Club Member

Joined: May 2007

Posts: 145,895

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From: 40 miles Northeast of Indy..

read and learn,,, most new system are stepped,, if its 2in from the heads,, usually its on the BB's not stock displacement...

Jun 10, 2010 | 12:45 PM

tmitchellof PG

Elite HDF Member

Joined: Sep 2006

Posts: 3,718

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From: Punta Gorda,FL

You can't get regular baffles to fit in 1-3/4" OD pipes. I had 1-3/4" OD, first generation,Samson Rip Saws on my bike for about 2-1/2 years before I got rid of them because I couldn't take the noise of the drag pipes, without any baffles, with my 103" engine.
They were basically drag pipes. I did a lot of searching for baffles to quiet them down, but the only ones available were the all metal ones that didn't lower the volume enough to make a difference.
Tom

Jun 10, 2010 | 01:47 PM

Samson_info

Former Sponsor

Joined: May 2010

Posts: 271

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Quote:

Originally Posted by 2006FLST

the smaller the pipe results in more velocity of the exhaust gases. so the 1 3/4" as compared to the 2" the 2" has less velocity. the back pressure would not be there at all with an open drag pipe especially the 2". the exhaust port diameter at the head is made for 1 3/4" pipe but if using torque cones you can create even more velocity. you should never run anything smaller than the 1 3/4" pipe on any Harley.
thank you,
JR

Last edited by Samson_info; Jun 10, 2010 at 01:51 PM.