Does Putting a High Flow Head Pipe on the 107 M8 "Transform" The Motor? - Road Glide Forums
Intake and Exhaust Intake and Exhaust Systems for Road Glides

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post #1 of 7 (permalink) Old 04-21-2018, 07:56 AM Thread Starter
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Does Putting a High Flow Head Pipe on the 107 M8 "Transform" The Motor?

I've put the Fullsac headpipes and baffles on all of our Harley's and never been disappointed. Amazing sound and great performance.

However, I've held off on putting the headpipe on the 2017 FLTRU for a couple reasons. One is the MOCO's crackdown on EPA violations and another is not wanting this bike to be "loud". But, to be fair, the Fullsac headpipes and baffles with sound batting have always had a nice note without being too loud on the Twin Cams.

So, I've tried to 'accept' the M8's unique sounds for the past year and have limited my mods to Reinhart cans with Fullsac sound insulation, a Ventilator intake and a Dyno tune that has the motor making 81 hp and 105 ft lb torque.

As you'd expect, it doesn't have the get-up-and-go of my 2013 FLHRSE5's 110" motor with the Fullsac headpipe, etc. at 96 hp and 112 ft lb torque, and forget about keeping up with the Honda F6B at 112 hp and 122 ft lb torque.

But, what's bothersome is what sounds like a ton of back pressure at the collector pipe & cat on WOT and the very uneven exhaust flow out the two tail pipes, where the left pipe pretty much functions as a by-pass under harder power output.

Definitely conflicted, but starting to lean towards doing the head pipe and just "talking out loud" to see if I can push myself over the edge to order the pipe at this point.

So, to those who have changed out the head pipe for an aftermarket pipe (not just gutting the cat), much difference did it make in terms of power and the sound of the motor / exhaust flow?
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post #2 of 7 (permalink) Old 04-21-2018, 10:06 AM
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I don't have an M8, but a few people on here have changed the head pipe out, warranty be damned, and had some good results. You may need to have another tune though, due to the new head pipe moving out more exhaust.

"I'd rather have a bottle in front of me, than have to have a frontal lobotomy." ~ Tom Waits
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post #3 of 7 (permalink) Old 04-21-2018, 10:18 AM
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The head pipe is just one piece in a performance package.

It limits what you can do with aftermarket tunes. But swapping it out is going to yield dick without a new tune and some free flowing cans on the back, as well as a free flowing air breather. More air in, properly mixed with fuel equals more exhaust out, and a bump in power. It all works together.

So decide how much power you want, and then figure out what it takes to get there. But do it as a package. No use in setting the exhaust up for 100 HP and then skipping the cams to hold the cost down. You'd be better off with setting the exhaust up for 75-80 HP and not killing off the low end.

With that said, if its the look you're after, then anything goes.
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post #4 of 7 (permalink) Old 04-21-2018, 02:48 PM
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I have a 2018 FLTRU with everything stock at this time. I also want more performance and sound, but am undecided if I will have any engine work done. I'm looking at the Arlen Ness air cleaner and Power Vision tuner. I'm considering the RC Components exhaust or D&D header and exhaust system. I usually ride in the 2500 to 3500 rpm range, so torque is more important than horsepower for me. I like a deeper performance sound, but I don't want to annoy my elderly widow next door. Once I commit to this, I will cancel my extended warranty since HD will not like me not going through a HD dealer for my upgrades.

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post #5 of 7 (permalink) Old 04-22-2018, 04:43 PM Thread Starter
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Appreciate the feedback and, yes... I know it would need to be dyno tuned again.

Just looking for any first-hand experience / impressions from someone who replaced the stock head pipe on their M8 motor with something like a Fuel Moto, Fullsac or other aftermarket head pipe.

That's the only element of the typical Stage 1 upgrade that I've not made as of yet: the intake / breather has been upgraded and the bike has Rinehart 4" slip-ons.
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post #6 of 7 (permalink) Old 04-22-2018, 05:56 PM
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Wink risk/reward

been there, done that. headers are the least important if you want more from your bike. why risk your warranty for a few more hp? the right way? put a harley tuner in, install harley torque cam, ......the stock headers with cats will flow plenty of air with an SE high flow, and you will be warranted. look at some dyno charts. the harley setup produces very good numbers WITH stock headers. most dealers will show you dyno after installation. ask to see some sheets before install if you don't believe me..........good luck
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post #7 of 7 (permalink) Old 04-23-2018, 07:09 AM
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I Put Rinehart Slimline Duals on,No Squished Pipe underneath like Factory A full Diamater Pipe,Arlen Ness Big Sucker Air Cleaner Power Vision An Dynoed.It made 88 hp an 113 lbs of Torque.Bike runs good much Stronger an way more power than my 103.I always run Full Exhaust an Have them Dynoed for a Proper tune An never have any problems.Dont really like messing with the moter,This 107 set up like this is a nice improvement over stock An a nice Step up from My 103 SG Sounds Good an is Reliable Like it A lot.


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