View Full Version : ULY Hackpipe

08-15-2009, 07:04 PM
Just playing around. I wanted something quite around idle for the stoplight commute, but deeper sounding than stock. I cut out the inner rear pipe so the first pipe exits without looping around, and now all 3 exit under full throttle. I considered dual outlets but figured it works fine stock with a single outlet and I was looking for more low end anyway. The packing is course stainless mesh. Other than slight popping when backing off, I'm very happy. Low deep rumble around idle and steady rpm. It's plenty loud under full throttle and pulls strong except, - MISTAKE! The pipe is from a lightning. The ULY kickstand is longer so it sits directly in front of the outlet. I'll pull it off and redirect it out of the way. Oh well, live and learn! My camera is at work so later I should be able to add a soundclip.


08-15-2009, 07:52 PM
very cool..

08-16-2009, 01:16 AM
Nice, Where would a person get those materials to do such a job. How much tone did it add. Did you lose much of the low end power on the bike.

08-16-2009, 03:04 AM
The Stainless wool came from McMaster Carr #7363T47 ($15.00) and the perforated tubing from Baron Custom Accessories (apx $45.00) The tubes are 1-5/8", 1-3/4", 2" OD. They are the same size as the stock pipes. The tone is very deep with all the stock garbage can tone gone. The screen and mesh I put in the rear was probably not necessary. Low end is stronger than before (feels like it anyway)

buellet proof
08-16-2009, 03:22 AM
That is really clean looking, real nice job..
I wonder if it would work ok without all that packing in it. With that much perf. it looks like it would get plenty of back pressure without it, that is if you want it louder like I would.
looks good

08-17-2009, 11:30 PM
I think it would be quieter without the packing, like a big resonator. Want it louder, use fine packing stuffed in tight, or leave the 2 pipes coming from the valve side solid? New exhaust tip misses the kickstand. So far, so good......

08-27-2009, 02:28 PM
Did you retain use of the stock flapper valve thing in the muffler?

08-27-2009, 11:26 PM
Yes I retained the valve, although it runs fine wired open. Next I may remove the valve and add a 2nd outlet. Maybe try one big perforated oval tube instead of three small round ones. I have a hundred ideas I would like to try but without a dyno, it's just guesswork (but fun!). Guys like MR Gongoleski(voodoo) and MR Drum(drummer) deserve a ton of respect for the hours they put in getting it right. From a performance standpoint, improving on what Buell engineers did is not as simple as it sounds.....

11-20-2009, 10:16 AM
Just checking, this mod is not going to upset the engine management if you dont re tune the EMS. ??I'm looking for the better sound but performance is already acceptable to me. I also think the back pressure if you retained the first pass into the rear section should be more than adequate for the EMS. ie no perferated tube on the first pass.
Cheers for the info

11-22-2009, 03:20 PM
I left my ECM alone and it ran fine(with stock air cleaner). An tuned ECM would probably help all Buells, including stock.
A solid first pipe would sound great but pushing the limited stock ECM. I considered leaving the first pipe alone but was building a commuter pipe and wanted it quiet near idle. If I left all three pipes alone and modified the rear section only, it would be easy and cheap. Call it the "Stage One gutted pipe". ???

11-23-2009, 02:02 AM
WOW awesome job. I was actually looking at doing something very similar using louvered cores from coneeng.com. http://www.coneeng.com/images/mufflers/muff2.jpg

My plan was to leave the main linlet tube intact ( to maintain the length of the pipe for tuning) and add the louvered sections to the other 2 pipes and increase the size of the exit port or as you said add another one. One addition I have been considering is adding a nipple to the inlet pipe to connect to my crankcase breather reroute lone and avoid a catch can. If I could develope an amount of vacuum doing this (venturi effect) I think it might be an added benefit of eliminating some of the crank case positive pressure.

Ok I am a definite newbee in the Buell scene so I am actually hoping for a little enlightenment on the error of my thinking. lol ;)

11-23-2009, 03:17 AM
i cut open mine over the exit and removed the curve also. i didnt use packing and it sounds bad ass. has a thump at idle but any throttle and it sounds like a rc51 on acid. and it still uses the flapper so i didnt do a tune. butt dyno says all ok.

11-23-2009, 04:29 AM
Correct me if I am wrong, and more than likely I am, but if you cut the curve out by the exit that is probably to make anything else you do inside a waste of time right? the exhaust gas should pass right out the exit ( path of least resistance ) instead of going back through the chamber into the other tubes.

I would love to hear how this sounds.

11-23-2009, 12:28 PM
The other two tubes flow gasses when the valve opens. Closed valve, exit through one tube. Valve opens, all three exit.

11-25-2009, 04:33 PM
I was under the assumption that the exhaust gas passes down the inlet tube (left side) into the chamber at the rear and then goes up the right side tube to the chamber at the front and passes down the center tube to the curved tube exit. When the valve is opened it allows a certain amount of exhaust to pass out of the inlet directly to the front chamber and then out the center tube, bypassing the left side tube and rear chamber completely. If the curved tube at the exit is cut that allows the gas to pass directly out nullifying any modifications you have done to the inside of the muffler.

I believe that the Buell engineers spent an amazing amount of time designing and testing this system with a LOT of computer time and the basics for a performance exhaust are right there we just need to free them up a little. I think the tube diameters and length (including inside the muffler) are "tuned" for torque and the chambers are for the EPA lol. I think the design you have is pretty damn sweet so I am going to try to copy your exhaust excpet for cutting the tube, which is probably good for higher RPM HP which I rarely use compared to the torque.


I am basing my assumtions on this diagram. I also found a performance auto exhaust I am posting for comparison that copied your design [smirk]


Once again please feel free to point out any errors on my part, I just want to get it right the first time.

11-25-2009, 10:04 PM
I think that you are right about not cutting the internal exit pipe off. This would really make it into a straight through pipe (almost).

If the three internal pipes were louvered as suggested, and the internal exit pipe kept in place the gas would still travel round the flow system, but some of the gas would escape out the louvers and through the centre/exit pipe. This would have a high flow rate and retain some back pressure. More noise and still have the torque.

Sounds like the way forward.

You do it! and if it works..... I'll do mine.

Ha Ha

Let me know how you get on. I am still deciding what to do with mine.


11-25-2009, 11:40 PM
I was getting ready to order the tubing from Barons but was wondering where you go the flanges ( reducers? ) on each end of the pipes. Did Barons provide them or did you oversize the pipe and use reducers to get everything to fit that clean?

11-26-2009, 02:01 AM
The perforated tubing matched the original sizes. The couplings were pieces of the stock pipes I cut out. I cut off 1/2 inch pieces and cut them open to fit over the perforated tubing. The 3 factory tubes are 1-5/8" - 1-3/4" - 2".(OD)

Harley big twin performance exhausts are usually based on a optimum length of around 30" (thanks joe minton). An old trick to increase horsepower on 40" straight pipes was to cut off 10". I feel the stock length is long to keep the noise down. That's why there is a resonator the the 2nd pipe and the 2 chambers are used, to break up the distance.

Packing is just a different way to muffle noise as opposed to resonators. A perforated tube wraped in packing will be quieter than solid tube and add some backpressure. My guess is if you leave the rear exit pipe intact and change the three like I did, it will sound like a Honda 90.

All this is based on a old guy(me) using guesswork and decades of past experience to come up with this pipe. I also wanted it quiet and will do another one with more sound next. Without a dyno, who knows if we're on the right track. It would not suprise me one bit if I'm full of crap!!

11-26-2009, 02:49 AM
All this is based on a old guy(me) using guesswork and decades of past experience to come up with this pipe. I also wanted it quiet and will do another one with more sound next. Without a dyno, who knows if we're on the right track. It would not suprise me one bit if I'm full of crap!!

You get some rep for that ;)[up]

11-26-2009, 04:58 AM
Thanks once again for the info. I will give it a shot as soon as I can and if you hear of an old guy in Kansas on a big Honda 90 you will know who it is lol. It definitely won't be the first time I screwed up a perfectly good piece of equipment. But by the off chance it works out it definitely gives us another option to look at. Maybe next we can figure out the EFI lol.

11-27-2009, 02:36 AM
Great stuff Hiwayman! I did lol. No matter how it sounds, it should run great. I have more internal muffler pics and other misc info so let me know if I have anything that may help you. I have turned my attention to the ECM. It's like going back to school learning all the options available and what they do. Give me a handfull of jets and I'm fine. Give me software and a mouse and it may never run again!

12-03-2012, 01:52 PM
Update for anyone following this thread and muffler build. It looks like I now own this exhaust, found it on ebay. I just installed and took it for its maiden voyage today. My finding so far:

1) Quieter than stock, or as quiet. May be 5% louder until for first 15 seconds warmup, but then is very quiet
2) Deep pulses of sound. Not as deep as all the other exhausts, but a huge improvement over stock without being obnoxious. Reminds me of a quieter, more mechanical/controlled sound than my Hawk. Kinda like a Hawk with 20% of the sound of a tuned import vtwin thrown in. Lawnmower, no more.
3) Smooth, consistant idle, smooth launch.
4) High rpm is about equal to stock.
5) There's a distinct power dip at 3500-4000 rpm. Upon comparing to my current map tuned to stock muffler with K&N, I found my fueling to be too rich in the center of the map by 10-15%. Maybe even 20% in spots. I've leaned things out for the second run, we'll see how much power it regains. For now though, this exhaust seems to suffer slightly in the midrange. It seems fine on the highway, but the power delivery stalls and the rpms slow in the climb through this region on 0-60 pulls.

I'm correct in assuming less fuel = less air = less power, right? Or is there another variable in exhaust I'm missing?

My guess is that this exhaust will feel identical to stock once tuned, just a hair deeper.