Making Your Milwaukee-Eight Sound Menacing: What’s Up in the Forums
Catalytic converters help keep emissions down, but they also kill the rumble of Harley’s Milwaukee-Eight. Here’s how to turn things up a notch.
Emissions gear is admittedly, for the most part, a buzzkill. But it is a reality that isn’t going away anytime soon. That fact has unfortunately affected every maker of motor vehicles, including Harley-Davidson. And while there’s nothing wrong with cleaner emissions or cleaner air, many aren’t exactly crazy that Harley’s new Milwaukee-Eight is noticeably quieter than the old V-Twin because of it. Including HD Forums member chilidipper.
“Can someone explain why the Milwaukee-Eight seems to be so much quieter than the V-Twin? Keep in mind I live in California. I am used to all the previous bikes that did not take much to put character into the sound of the bike. Dynas with V&H Long Shots or Bassanis on Bagger, these sounded like beasts (loved the sound). A pretty raspy sharp pop from Bassani. Seems like I am struggling with my RKS to get a decent sound. I have upgraded to a K&N and V&H high-output slips with stock headers. Just put on the slips 3 days ago, but I am afraid I made a mistake with them.”
It’s an unfortunate problem that can be blamed on one simple culprit.
“Catalytic converters,” says d_slat, succinctly.
But there are ways around it, of course. Even without having to delete the cats and void your warranty.
“When I was shopping for pipes, I was told to take the Hi-Outputs off my list because they won’t work well on a stock or stage one bike,” says sixguns. “Also, smaller diameter will make more decibels. Have you looked at the S&S Grand Nationals?”
Several others suggest a tune above anything else.
“Assume you got tuning adjusted, with SE or aftermarket device,” says Fullbore55.
“Can’t help with the sound. But you should do a tune,” adds TriGeezer.
Regardless, some have found it difficult to get the desired sound out of their Milwaukee-Eight, regardless of what they’ve tried.
“It’s very hard to get a good sound with the new 4-valve heads and the stock head pipe,” admits lyork.“I’ve had three different slip-ons and now a fourth (Magnaflow) that I’ll try next spring. All I can suggest is to watch the videos and try to decipher which ones have a sound you like the best. There tends to be used slip-ons in the for sale section on a fairly regular basis as members like me search for a sound we like.
If you’re willing to risk voiding the engine warranty, de-catting the stock head pipe is the way to go (or an aftermarket one). Then you can get a great sound out of the M8 and more power as well.”
Others agree that removing the cat is a must, despite the downside to doing so.
“Catless header, different cam, and whatever slip-ons will get you a thousand times better,” says purpledeuce.
And it seems like xnysgt might have already found the perfect solution.
“Warranty topic aside, a Stage I will be the least expensive and quickest way to fix this (head pipe, slip-ons, the crux of the sound part). The cat is stifling and what MoCo did with the odd sized outlet pipes is nothing more than a play at proprietary ‘aftermarket’ equipment. When there weren’t many options at the M8’s initial release, I decided that rather than de-cat the OEM pipe and wait for slip-ons I may or may not like after buying, I just waited for a good head pipe for the M8 that would give me matched pipe outlet sizes so I could use any ’16 and earlier slip-ons. The market was/is flooded with great products in this range.
For my ’17 RGS I did Bassani Down Under true duals paired with Specialty Inc. DNA (CFR knockoff) slip-ons, Arlen Ness Monster Sucker AC intake, and a custom tune from Fuel Moto via Power Vision II. It’s loud with a bit of a nasty growl, but that was my goal.”
So maybe there’s hope for the Milwaukee-Eight, after all. There are plenty more useful tips on unleashing an appropriate sound for your M8 here. And after you finish checking them out, be sure and “sound” off with your advice for making Harley’s new powerplant really sing!
