I've put together a helpful article on our FM University site on Milwaukee-8 displacement on the various engines and big bore kits to help avoid confusion among these engines as the same displacement can be established with different bore & stroke combinations.
Let's start with the bore & stroke of the stock Milwaukee-8 engines:
H-D Milwaukee-8 107″ = 3.937″ bore X 4.375″ stroke
H-D Milwaukee-8 114″ = 4.00″ bore X 4.5″ stroke
H-D Milwaukee-8 117″ = 4.075″ bore X 4.5″ stroke
Harley SE Stage III and IV kits:
Milwaukee-8 Stage III/IV 114 kits = 4.075″ bore X 4.375 stroke
Milwaukee-8 Stage IV 117 kit = 4.075 bore X 4.5″ stroke
Aftermarket big bore kits
You have quite a few options here, it all depends on your build objectives and if you are boring the OEM cylinders or you are replacing the cylinders with aftermarket. Note the factory cylinders are different between the 107 engines and the 114/117 engines, the 107 M8 cylinders can only be bored to 4.125″ (117″ CI), however the factory 114/117 cylinders have a thicker sleeve that can be bored to 4.180″ (124″ CI). The case spigot bore is the same between each engine. The aftermarket cylinders we are referencing have a thicker liner than the OEM cylinders yet still fit the case spigot without machining.
OEM bored cylinder examples:
Milwaukee-8 117″ big bore for 107″ engines = 4.125″ bore X 4.375″ stroke
Milwaukee-8 124″ big bore for 114/117 engines = 4.180″ bore X 4.5″ stroke
Aftermarket cylinder examples:
Milwaukee-8 120″ big bore for 107 engines = 4.180″ X 4.375″ stroke
Milwaukee-8 124″ big bore for 107 engines = 4.250″ X 4.375″ stroke
Milwaukee-8 128″ big bore for 114/117 engines = 4.250 X 4.5″ stroke
Nice! Thanks for the chart. :up:
thanks! :up: :agree:
Copying it and saving it to my computer as we speak. Thanks!
Thanks for your time and effort here Jamie.
One thing that I would like to see added is the wall thickness of spigot on these combinations.
What's the advantage to doing an SE Stage 3 on a 117? 2 friends are doing it to there CVO's.
Wonder what a Square bore and stroke or even a short stroke M8 would run like and is anyone thinking of trying that.
Adding to that list is this possibility as well.
Milwaukee-8 114″ big bore for 107″ engines = 4.075″ bore X 4.375″ stroke
Need to clean your glasses, 1st line 2nd set of numbers :wink:
Quote from: DTTJGlide on March 01, 2019, 07:42:07 PM
Need to clean your glasses, 1st line 2nd set of numbers :wink:
Unless someone changed something, I don't see what you are talking about.
Quote from: Smarty on March 04, 2019, 08:17:13 AM
Quote from: DTTJGlide on March 01, 2019, 07:42:07 PM
Need to clean your glasses, 1st line 2nd set of numbers :wink:
Unless someone changed something, I don't see what you are talking about.
Is it this in the second set of numbers?
Milwaukee-8 Stage III/IV 114 kits = 4.075″ bore X 4.375 stroke
H-D Milwaukee-8 114″ = 4.00″ bore X 4.5″ stroke
No 4.00" bore. Just a typo
You would have to bore the cases to achieve square period. I've built a 124 M8 and a 128 M8 and both run great, MAJOR improvement over stock. That being said my gut says the 4.25" bore with a 4.375" stroke would be the best all around engine. That would yield 124 with a stock 4 3/8 stroke not square but nearly.
Quote from: trex on February 28, 2019, 11:18:44 AM
Wonder what a Square bore and stroke or even a short stroke M8 would run like and is anyone thinking of trying that.
Jaime,
First thanks for posting,
Based off of your statement above . . .
"Note the factory cylinders are different between the 107 engines and the 114/117 engines, the 107 M8 cylinders can only be bored to 4.125″ (117″ CI), however the factory 114/117 cylinders have a thicker sleeve that can be bored to 4.180″ (124″ CI). The case spigot bore is the same between each engine. The aftermarket cylinders we are referencing have a thicker liner than the OEM cylinders yet still fit the case spigot without machining."
It seems like some take-off (or purchased) Cylinders from the 114/117 could be installed onto a 107" and bored to 4.180" to reach a 4.180"X4.375" = 120"
Perhaps would have to cut the length down?