I’d like to know what the deal is with Harleys and why their new owners immediately remove the stock, muffled, exhaust system and replace it with straight pipes?
I’d also like to know why they get away with it?
I mean, if I did the same thing to my car, I’d get pulled over and handed a ticket PDQ. So, why do cops seem to ignore Harleys? Is it because a lot of cops HAVE Harleys? What’s the deal???
Because that is how a Harley is supposed to sound, part of the heritage and image of the Harley. Another reason is to let it breathe like it is supposed to. The term straight pipes is a bit misleading though as it tends to refer to a pipe with no baffles at all. If you ran pipes with no baffles at all it would be very loud and you would lose performance without the needed backpressure. The stock (quiet) pipes that come on a Harley do not perform like the aftermarket pipes do.
When I purchased my current Harley in '99 the first thing to go was the stock pipes, this was before it had 10 miles on it. Along with the exhaust modification came a carburator rejet and a highflow aircleaner, all in the name of getting more air/fuel through the engine and getting more power out of it. And a great sounding exhaust to boot!
As far as getting away with it, not always. I have been through areas that will ticket you if your exhaust is above a predetermined db. I have also known one town where the police would actually stick their nightstick into the exhaust pipes to check for baffles, no baffles = ticket.
Unless your Harley is a two-stroke, backpressure from the exhaust will have no effect on performance. Changing the pipe on a two-stroke bike can have an immediate effect on performance, but that’s not going to happen with a four-stroke.
And shoving a stick down an exhaust pipe is stupid. Many pipes have spiral baffles that don’t necessarily extend all the way to the centre.
Bikes come out of the dealer with an air/fuel mixture designed to pass clean-air regulations. However, what’s best for the air isn’t going to give you the best performance. Rejetting the air/fuel mix is the best way to do it. If you’re going to slap a new pipe on the four-stroke bike, you’ll have to rejet in order to get that peak performance.
As for why they do it-- there’s a belief among some riders that loud pipes save lives. Since the noise of the exhaust is directed backwards, and most accidents happen from head-on or side-on collisions (even with riders who have quiet pipes), it’s a rather dubious assumption that noise directed to the rear will prevent someone from running into you.
As for getting away with it-- how many cops have you seen armed with noisemeters? Are there even any noise pollution regulations in your neighbourhood?
Are there noise pollution laws in my area? With respect to motor vehicles? Dunno. And no, I doubt sound-level meters are standard police issue. :^)
I was just trying to get a feel for why Harleys are so obnoxioulsy loud. And why owners, indeed, want to make them even more so. And it seems to be because “they like it that way”. Must go with the “bad boy” image Harley riders seem to like to perpetuate. Doesn’t seem to be any other reason for it, other than a minute power boost.
It still seems to me that any four-wheeled vehicle that you could hear coming from a mile away would be begging for an excessive noise ticket, yet I’ve never heard any Harley rider I know complaining about getting hassled for it. Personally, I find the noise they make obnoxious and excessive. But that’s just me.
I remember an article in HotRod Bike magazine a few years ago where they dyno tested bikes with baffles and without. They were getting better results with the baffles than without in most cases. They also mentioned having the proper amount of backpressure to tune it right. I wish I could supply a link but I cannot find it at this time, and when I read it before it was in the magazine.
I have removed the baffles from my pipes once to see what the result would be. It was really flat when opening the throttle up at around 50-60 mph. I lost power in a few ranges like that. That is just going by the seat of the pants feel, I don’t have any dyno numbers to back it up but I could feel the difference. The baffles went right back in the same day.
As far as shoving a stick down a pipe being stupid, I agree. I didn’t say it was smart, just said that they were doing that.
Stock Twin Cam 88 Harley engine specs - 53hp and 66ft punds of torque. With a simple exhaust swap to Screamin Eagle pipes, rejet carb and install highflow aircleaner 69hp and 79ft pounds of torque. Not really minute gains for as simple as the mods are.
Link… http://www.nightrider.com/biketech/hplist_twin_cam.htm
Ah, well, that IS a bit more significant, isn’t it? I appreciate the insight, GiLL, and hope you didn’t take any offense to my comments, after you were so kind to reply to my question. :^)
Cheers
I don’t get offended too easily. And as far as you not liking the sound I figure to each his own. For me the sound of a Harley engine pulling some low end torque out of a curve or up a hill and hearing and feeling it gets my blood pumping. I have been riding Harleys for about 12 years now and wouldn’t have it any other way.
Harleys are all about image. If you are familiar with the range of motorcycles that exist as competition to the Harley, you will know that there are motorcyles that will outcompete the Harley in most areas except image and the community that is devoted to customizing bikes. However, modifications to the exhaust system may result in better performance…although I feel that the Harleys have more than enough power for 99.5% of all applications.
So most folks buy their Harley for the image…and what better way to have people notice you than to have them look at a loud sound.
BTW…I’m not saying that Harleys are bad bikes, nor am I trying to start a flame war. They just represent a certain segment of the motorcycling choices.
Something you should be aware of: It’s often not a matter of liking or not liking the sound. The pressure waves generated by an unmuffled Harley can have adverse physical effects on some people.
For some reason, I have rather sensitive ears. If I make a phone call and the ring-tone is especially loud, and if I hold the receiver too close to my ear, the minute pressure waves cause my vision to flutter with the pulses. It’s extremely uncomfortable.
The same thing happens when there is an unmuffled Harley beside me. With every pulse of the engine, with every “sweet note of Harley music”, the pressure wave causes discomfort. My vision flutters at the same rate as the V-twin power strokes. It’s very, very uncomfortable.
Ain’t that the truth.
From DiLLiGaF’s post, his Harley V-twin, of what, 880 cc is it? Puts out 53 HP stock. A new Honda CR250- less than a third the displacement- puts out 44 HP.
If you wanted to more directly compare 4-stroke/displacement, compare a CBR900RR for HP/cc.
But, it’s all about image, pure and simple. Loud pipes are part of the image, and claims of additional HP aren’t much more than an after-the-fact excuse.
That reminds me of when I took my lessons. For our street practice, we could ride a 250 cc Virago, 250 cc Marauder, 500 cc Blast!, or a Harley Sportster. That pretty much said it all as far as what’s considered a safe bike for a newbie 
Actually my engine is 1450cc also known as 88 cubic inches. Not that it helps my case in the hp numbers. I think you are comparing apples and oranges when using the CBR900RR to compare with. While that will pull ~110hp stock it doesn’t get into the power band until around 7-8000 rpm and doesn’t hit the max hp until 10,500 rpm. You want to talk about loud?
I couldn’t find the torque specs on the CBR900RR but I did find some for the VTR1000SP1. If you look at those numbers it hits max hp of 135hp @ 9500 rpm, but only nets 79 ft pounds of torque. All that hp and still getting the same torque as my 69hp V-Twin. Hp numbers are bragging numbers, torque figures are what you feel in the seat of your pants when you roll on the throttle. Would I race one? Hell no, different bikes designed for different purpose, apples and oranges.
Link to specs for Honda VTR1000… http://www.mtv411.com/motorcycle/pictures/honda/vtr-1000sp-rc51.htm
Actually my engine is 1450cc also known as 88 cubic inches. Not that it helps my case in the hp numbers. I think you are comparing apples and oranges when using the CBR900RR to compare with. While that will pull ~110hp stock it doesn’t get into the power band until around 7-8000 rpm and doesn’t hit the max hp until 10,500 rpm. You want to talk about loud?
I couldn’t find the torque specs on the CBR900RR but I did find some for the VTR1000SP1. If you look at those numbers it hits max hp of 135hp @ 9500 rpm, but only nets 79 ft pounds of torque. All that hp and still getting the same torque as my 69hp V-Twin. Hp numbers are bragging numbers, torque figures are what you feel in the seat of your pants when you roll on the throttle. Would I race one? Hell no, different bikes designed for different purpose, apples and oranges.
Link to specs for Honda VTR1000… http://www.mtv411.com/motorcycle/pictures/honda/vtr-1000sp-rc51.htm