1980 sportster exhaust question
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Tourer
Joined: Mar 2012
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From: NC
1980 sportster exhaust question
I recently got custody of my sons 80 Sportster while he's deployed overseas. I'm restoring it for him. He thinks he gave it to me. Anyway, Now that I have most of the electrical issues worked out, well, lets just say it runs. I was looking at the exhaust and wondering why two separate pipes would be connected by a small tube. I was thinking this was an add on from some other scrapped bike. Then I came across a pic of somebody's project 80 sportster with the same muffler. I'd be ok with it but the tach cable has melted away the outer plastic sheath because it passes across the smaller tube connecting the two main pipes. Why?
Road Captain
Joined: Sep 2011
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From: Calgary, Canada
I believe it's just to balance the exhaust pressures. The newer bikes have the crossover as well but it's now hidden behind the mufflers.
ETA: Found this info:
http://www.americanrider.com/output.cfm?id=1021987
ETA: Found this info:
Most Harley motorcycles have small mufflers relative to their engine displacement. Those small mufflers must also be quiet, and that combination results in limited airflow which, in turn, limits power output. A crossover pipe allows the exhaust gasses from one cylinder to flow through both mufflers, thus reducing the restriction and adding a bit of power.
Crossover pipes can also improve mid-rpm torque if they are properly located. Triumph first discovered this when they introduced an exhaust crossover pipe to their American Triumph Bonnevilles in 1964. The original purpose was to increase the airflow through the smaller mufflers that we Americans preferred. However, they also discovered that the crossover added performance in the mid-rpm range.
Crossover pipes can also improve mid-rpm torque if they are properly located. Triumph first discovered this when they introduced an exhaust crossover pipe to their American Triumph Bonnevilles in 1964. The original purpose was to increase the airflow through the smaller mufflers that we Americans preferred. However, they also discovered that the crossover added performance in the mid-rpm range.
Last edited by CanuckSporty; Mar 9, 2012 at 08:21 PM.
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Joined: Oct 2007
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From: USA
Your son has a stock exhaust system on his bike. Nothing wrong with that (see attached pic). Leave the cross-over pipe alone and relocate or adjust the tach cable as needed.
Last edited by run1fsr; Mar 10, 2012 at 08:33 AM.
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Tourer
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From: NC
I'm only saying this because I don't know **** about motorcycles. But why would they design for the tach cable to cross over an exhaust pipe? Move the tach cable? The cable comes straight up just behind where the Generator is attached on the right side of the bike. Looks like there was a heat shield across the connecting tube. Would that have prevented it from getting hot enough to burn the cable? Then, what hose is supposed to be connected to the thing sticking out of the housing where the generator is attached?
Link to picture: https://www.hdforums.com/forum/membe...ach-cable.html
Link to picture: https://www.hdforums.com/forum/membe...ach-cable.html
Last edited by marine_hm@hotmail.com; Mar 11, 2012 at 10:29 PM. Reason: linked picture did not get attached like I wanted.
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From: Bedford UK
Bikes used to have two separate pipes, then in the early 60s Triumph fitted that extra pipe on their parallel twins and discovered by accident that it improves torque! So lots of other twin manufacturers did the same, including Harley, who still fit them today on the very latest models. So that pipe does improve your bike and is worth keeping. It might be worth making a support bracket to keep that tacho cable away from the pipes?
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