Milwaukee 8 Engine Problems
Cruiser
Joined: Mar 2007
Posts: 163
Likes: 32
From: Amsterdam , The Netherlands
The mechanics at my very fine and friendly HD-dealer call it common facts what they see very often if they take M8 engines apart . 
Of course they all are familiar with these less strong points ,...and they honestly talk it over with me .( just like friends do
)
--------------------------------------------------
I've ordered today a low budget ( from Aliexpress ) endoscope , so that I can check possible carbon build up myself , just before the HD maintenance visits.
-----------------------------------------------------------------------------------------------------
Let me make myself clear that I wish you all the very best - , reliable - and flawless M8 motorcycles ,....and no troubles for now and in the future
( and if you should keep it stock , or no further upgrade than Stage 1 ,....and ride the bike nice and gently ,....is that what probably will happen )
Of course they all are familiar with these less strong points ,...and they honestly talk it over with me .( just like friends do
)--------------------------------------------------
I've ordered today a low budget ( from Aliexpress ) endoscope , so that I can check possible carbon build up myself , just before the HD maintenance visits.
-----------------------------------------------------------------------------------------------------
Let me make myself clear that I wish you all the very best - , reliable - and flawless M8 motorcycles ,....and no troubles for now and in the future
( and if you should keep it stock , or no further upgrade than Stage 1 ,....and ride the bike nice and gently ,....is that what probably will happen )
Last edited by sjoko; Aug 29, 2023 at 02:43 PM.
Road Warrior
Joined: Nov 2022
Posts: 1,538
Likes: 543
From: MN
The mechanics at my very fine and friendly HD-dealer call it common facts what they see very often if they take M8 engines apart .
Of course they all are familiar with these less strong points ,...and they honestly talk it over with me .( just like friends do )
--------------------------------------------------
I've ordered today a low budget ( from Aliexpress ) endoscope , so that I can check possible carbon build up myself , just before the HD maintenance visits.
-----------------------------------------------------------------------------------------------------
Let me make myself clear that I wish you all the very best - , reliable - and flawless M8 motorcycles ,....and no troubles for now and in the future
( and if you should keep it stock , or no further upgrade than Stage 1 ,....and ride the bike nice and gently ,....is that what probably will happen )
Of course they all are familiar with these less strong points ,...and they honestly talk it over with me .( just like friends do
)--------------------------------------------------
I've ordered today a low budget ( from Aliexpress ) endoscope , so that I can check possible carbon build up myself , just before the HD maintenance visits.
-----------------------------------------------------------------------------------------------------
Let me make myself clear that I wish you all the very best - , reliable - and flawless M8 motorcycles ,....and no troubles for now and in the future
( and if you should keep it stock , or no further upgrade than Stage 1 ,....and ride the bike nice and gently ,....is that what probably will happen )
Seasoned HDF Member
Joined: Mar 2021
Posts: 18,252
Likes: 3,679
From: backwoods
One theory was this even started with 103" and getting hotter. I wonder if 96/6 speed and mounting starter directly to primary, which in the past added a small amount of venting.
One interesting thing is the change in fluid levels in 6 speed trannys and primarys. Did they know something was going on?
Never had a primary vent.
Replacing oil pump, on new machine is BS, especically if you have to pay for it.
Last edited by Rounders; Aug 29, 2023 at 04:46 PM.
Club Member
Joined: Apr 2013
Posts: 5,810
Likes: 3,810
From: Cape Cod
One of the theories I heard is, it is more promiment in touring bikes, because they get rode more, and being rode on long days they get hotter.
One theory was this even started with 103" and getting hotter. I wonder if 96/6 speed and mounting starter directly to primary, which in the past added a small amount of venting.
One interesting thing is the change in fluid levels in 6 speed trannys and primarys. Did they know something was going on?
Never had a primary vent.
Replacing oil pump, on new machine is BS, especically if you have to pay for it.
One theory was this even started with 103" and getting hotter. I wonder if 96/6 speed and mounting starter directly to primary, which in the past added a small amount of venting.
One interesting thing is the change in fluid levels in 6 speed trannys and primarys. Did they know something was going on?
Never had a primary vent.
Replacing oil pump, on new machine is BS, especically if you have to pay for it.
You didnt say ANYTHING!
Road Warrior
Joined: Sep 2016
Posts: 1,887
Likes: 1,059
From: SE Washington
Hi everyone, I am well aware that the early M8 engines from 2018 - 2020 had their fair share of mechanical issues. Am in right in thinking that the problems have been ironed out in the 2023 models? I currently have a 2015 twin cam and am think of upgrading to a new fatboy but I keep hearing things like stick with your twin cam
new M8s are nothing but trouble
Are they right? I am interested to hear from anyone that has one and whether theyve had a good or bad experience with it
Get one and don't look back. Just add gas and go.
From 2020 on, the stock oil pump is perfectly fine for anything you want to do, cam only, big bore, or just stock. I have zero issue with someone wanting to use aftermarket. S&S and fueling make good stuff, but to say that the someone looking at getting new bike needs to also upgrade the oil pump is just ignorant and foolish, and should not be listened to. Also, Fattyonafatboy, since you're looking at getting a Fatboy... sumping has never been an issue with softails due to a different case design for the dual counterbalancers. Get one. I'm confident you won't be disappointed.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Club Member
Joined: Apr 2016
Posts: 11,544
Likes: 8,376
From: Inland NW
Who is putting new oil pumps in new bikes under warranty? Please stop spreading your BS. Go away.
Seasoned HDF Member
Joined: Mar 2021
Posts: 18,252
Likes: 3,679
From: backwoods