Home / Site Map / My Harley Blog /

SuperTrapp Megaphone Series Slip-ons

By Wom Battle

I've made a few changes to the exhaust system on my Harley-Davidson® Road King® since I bought it, the first a pair of Vance and Hines Classic Slipons fitted at the first service. A great sound and a little more performance.

Later, while not exactly exhaust related, came the upgrade to the '09 motor by way of the 103 Phase II kit which really benefited from the "openess" of the slipons.  Bigger engine and bigger sound too! 

The third phase of the "sound of Road King" was the fitting of a set of Vance and Hines Power Duals which had the effect of creating an extremely pleasant thump, particularly when the Road King was opened up. Performance was enhanced again very nicely thanks!

However, over time and spending longer days on the bike, even with ear plugs, the thumping exhaust could become a bit too much, particularly for a pillion. A couple of hundred k's without ear plugs was out of the question.

In terms of legality and noise I hadn't been too concerned. At the time I was creeping up on 60,000 kms and had never been pulled over for noise.  However, the local rozzers, bless 'em, decided to have a bit of a crack down on noisy pipes in our local area and bikes I thought might have been quieter than mine were being defected.  It got me to thinking so I took the white beast down to the Guru who whipped out his trusty noise meter.

I fired up my Harley-Davidson, revved it a bit, but not to the point I knew it was going to get loud and the reading was done ... XX3dB(A) where XX should be numbers but I'm not stoopid enough to write em down. I decided that a change was in order, particularly given at the time I was planning the Darwin trip and love my ear drums.

I still had the stock slipons in a box, however with the 103 kit and other work done to the donk the Guru discounted them immediately as a sensible option, too restrictive. I set him a goal of finding a solution that would work for performance and work for the ear drums and after a day's research he came up with a set of Supertrapp Megaphone Slip-ons at around $900 fitted and run over the dyno. 

I'd already had experience with SuperTrapp, my 98 Road King Classic had a 2 into 1 unit that I really liked. Without getting too technical they have closed end caps and a series of discs that you can insert into the rear of the slip-on just before the end cap.  Less rings means less noise, possibly more torque.  More rings, more noise and more power, they call this tuneable.  It seemed like a sensible option so I left it with him.

A couple of days later I went back and could see that the Guru was happy with his work. My Harley-Davidson had been quietened significantly by the SuperTrapp Megaphones without sounding weak and the dyno showed a 5% increase in torque down low.  The dyno also revealed a comparitive loss of top end power over the Vance and Hines, but the Guru had warned me about this so I wasn't upset.  Touring two up with luggage and an aversion to speeding fines means the additional torque would be very welcome. The Guru's verdict was that while riding around not drawing attention to myself the bike wouldn't either, mission accomplished. The sound meter was happy enough for me.

It was a bit strange riding away, I've not been one for music and distractions and realised I rode by ear/feel quiet a bit, so without feeling the familiar thump it took me a little while to get used to when to change gear while riding conservatively in traffic. Opening up the throttle was a different matter, while not a "through your body thump" it still has a great sound that let's you, and everyone near you, know it's there. 

The biggest difference and best aspect of the change for me is at touring speed.  The constant dual thump has transformed into a very pleasant background rumble that's not uncomfortable without ear plugs (on the occasions I've forgotten to put them in).  The extra torque down low is a very nice side effect, I noticed the extra pull up steep hills in 6th gear and the Harley-Davidson was even more ready to accelerate from lower revs when overtaking saving the odd change down.

The loss in top end power is noticeable but to be honest I rarely get there on the road.  I guess if I was going to need the power next time I'm at Eastern Creek I could always duck back to the Guru and get him to stick a few more discs in.  That's one of the features of the SuperTrapps I really like, you can tune them. I might decide one day to play with the discs to see what the effect is, but for now I'm very comfortable with the new sound and very happy with the SuperTrapp Megaphones.

In terms of looks, I don't have an issue with the end caps, they've turned a nice bronze colour with use. Some don't like them.  The profile of the exhaust isn't startlingly beautiful, it looks a little narrow joining into the V & H Power Duals but not "ugly". I guess if I had the bucks, or cared too much, I might look at some SuperTrapp headers but not for now.  My enthusiasm for my Road King has transferred from form to function over the last few years racking k's up on it.

So, the SuperTrapp Megaphone slip-ons are a highly recommended solution if you go touring and want more than the original equipment exhausts will give you power without the noise and risk of a completely opened up system.

Disclaimer: My review is based on my personal experience of them. I am not saying they are legal and I'm no EPA expert. So don't call me if you get a set for yourself and have trouble with the rozzers.  If you can read this you are big enough to make your own decisions and take your own risks.  If in doubt, stick with the OEM's.



Disclaimer: This non commercial website and its content is not affiliated with or associated in any way with the Harley-Davidson Motor Company, Harley-Davidson Australia, the Harley-Davidson Owners Group® or any Harley-Davidson® Dealers in Australia.  The use of the terms Harley-Davidson, and Road King® are unavoidable because that's what I own and ride.  This website,  called "My Harley Davidson" , and any opinions or comments expressed herein are purely about my Harley-Davidson Road King ownership experience, a truly great experience at that. I have no intention whatsoever to infringe on any trademarks or copyright ownership of the Harley-Davidson Motor Company or anyone else.

May 2024