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Why don't newer big twins have the potato sound?

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Old 11-19-2010, 05:10 AM
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One factor for a different sounding engine is the bore to stroke ratio. To get the bigger displacements HD increased the bore primarily. It was the long stroke that gives the old Shovels and Evos that "potato" sound. Also read recently in a "Hot Baggers" Mag article that any idle below 1000 rpm delivers a shock to the crank shaft as the slow turning engine tries to cycle and can damage the lower end. If I can find the exact quote/article I'll pass it on. Oh, another big factor I think is the stock exhaust on the newer Harley's. I had one pull up next to me at a red light a few years ago and I swear it sounded like a Honda; it was a sporty if I recall.
Old 11-19-2010, 05:53 AM
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Much higher idle speed and EFI!!!
Old 11-19-2010, 06:12 AM
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Doesn't really matter to me... Still sounds better than those rice burner bikes IMO!
Old 11-19-2010, 06:25 AM
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My 04 Softail has a carb and Samson Big Guns. It REALLY sounds like a Harley. In fact, I may get baffles to quiet it for riding to work. However, even the most stock-exahaust, EFI new from the showroom Harley still sounds enough like a Harley to be distinguishable from everything else by sound alone, as soon as you hear it. Honda and Yamaha and Victory may make bikes that look like a Harley from a distance, but you can tell them apart by sound before you can do it by looks.
Old 11-19-2010, 06:37 AM
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It would appear that the loss of the potato is down to the 96 engine having an oil pump that requires higher rev's to make sure that the oil gets to where its needed. I must admit I miss the potato sound, the new bikes sound quite modern on tick over. Even changing pipes has little effect.
However we do need to move with the times, or buy an older bike.
Old 11-19-2010, 06:42 AM
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I don't think anyone yet has the correct answer. Po-ta-to Po-ta-to is a three beat sound coming out of a two cylinder engine. Modern Harleys only have a tater tater sound.

The Potato Potato sound was produced by the old ignition, which fired both spark plugs at the same time, producing a "wasted" spark on each cylinder's exhaust stroke. Because there is a 405 degree difference in the stroke from the rear cylinder to the front on each revolution, when the rear cylinder fires on its compression stroke, the front exhaust valve is still open, unburned gases are ignited in the front exhaust by the "wasted" spark, causing the first beat of the potato sound. The modern ignition fires each plug separately at the proper time.

Add in the richer fuel mixture from a carb which loaded up the exhaust with unburned gases, and a slow idle, and that's why the old bikes had the classic sound we all loved.

Japanese bikes say "rice-a-ro-ni".

Last edited by MNPGRider; 11-21-2010 at 05:09 PM.
Old 11-19-2010, 06:46 AM
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Wouldn't revert to old technology just for the sound alone. Would need a better reason.
Old 11-19-2010, 07:22 AM
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Originally Posted by sageone View Post
Wouldn't revert to old technology just for the sound alone. Would need a better reason.

I wouldn't buy a new bike for technology alone. Different strokes for different folks. I will stick with my carbed bike.
Old 11-19-2010, 07:49 AM
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This is true, much easier to work on that's for sure.
Old 11-19-2010, 07:59 AM
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Between the EFI, emissions and newer style ignition the sound has been changed. The new sound is simply " tater, tater, tater, tater.
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