117 and 124 differences
Road Warrior
Joined: May 2011
Posts: 1,956
Likes: 437
From: florida
I think the sponsor advice is clear simple and correct. 124 is safe if compression in check, oil cooler strong, and tune spot on. Traffic or no traffic, don't make the 124 a heat seeking missle and all should work out for longevity. Don't over analyze it.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
Certainly old chap! The 124" engines Joe mentions have their origins in Evo days, with their longer stroke, while the 117" is based on the shorter stroke twincam.
Let's briefly take two V-twin engines, of the same capacity, but of different bores and strokes. At a given rpm, the long stroke engine will have the highest piston speed, which occurs when the piston is at mid-stroke. The short stroke engine will have the lowest piston speed.
Piston speed is important, especially in racing engines, because technology limits the maximum speed we can safely run pistons at and keep them properly lubricated. This in turn limits the maximum rpm that we can safely run the engine up to, hence the power that we can extract from it. A very short stroke engine, such as a Jap multi, can run to much higher rpms, before it hits the piston speed limitation.
As a sweeping generalisation, a long stroke engine will tend to give more torque and lower power than a short stroke engine, also it's max rpm will be a little lower. Having said that, we mostly discuss road-going engines in here, so IMHO piston speed isn't so important for most of us.
We have examples of long stroke engines, such as 89" Evos, which can run up high mileages reliably and probably give a Twincam 88" a good run for it's money. The 89" is 3.5" bore and 4.625" stroke, while the 88" has a 3.75" bore and 4" stroke.
Hope that helps!
Let's briefly take two V-twin engines, of the same capacity, but of different bores and strokes. At a given rpm, the long stroke engine will have the highest piston speed, which occurs when the piston is at mid-stroke. The short stroke engine will have the lowest piston speed.
Piston speed is important, especially in racing engines, because technology limits the maximum speed we can safely run pistons at and keep them properly lubricated. This in turn limits the maximum rpm that we can safely run the engine up to, hence the power that we can extract from it. A very short stroke engine, such as a Jap multi, can run to much higher rpms, before it hits the piston speed limitation.
As a sweeping generalisation, a long stroke engine will tend to give more torque and lower power than a short stroke engine, also it's max rpm will be a little lower. Having said that, we mostly discuss road-going engines in here, so IMHO piston speed isn't so important for most of us.
We have examples of long stroke engines, such as 89" Evos, which can run up high mileages reliably and probably give a Twincam 88" a good run for it's money. The 89" is 3.5" bore and 4.625" stroke, while the 88" has a 3.75" bore and 4" stroke.
Hope that helps!
Thanks grbrown! Guess I never took the time to think that the longer stroke required the piston to move faster at an equal RPM. It's something they didn't teach me in school...not that I paid much attention to anything they did. 
Road Warrior
Joined: Apr 2009
Posts: 1,258
Likes: 114
From: Jackson, Ohio
A lot of people confuse piston speed with rpm. 1000 rpm's is 1000 rpm's. You move the center of the rod out farther from the center of the crank, the piston has to travel faster to make every revolution.
Tourer
Joined: May 2007
Posts: 496
Likes: 4
From: CT
i had scott at hillside build a 117 for me..now have close to 20k on her with a wood 9f at 11.0cr..Doesn't burn a drop of oil and ride in traffic quite a bit..Have a great tune and a professional build and youll be good to go.. Havent met a match yet on the road that could keep up..
marc
marc
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
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
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Thread Starter
|
Road Master
Joined: Jun 2012
Posts: 1,088
Likes: 2
From: Mo
i had scott at hillside build a 117 for me..now have close to 20k on her with a wood 9f at 11.0cr..Doesn't burn a drop of oil and ride in traffic quite a bit..Have a great tune and a professional build and youll be good to go.. Havent met a match yet on the road that could keep up..
marc
marc
I'm sure there are others on here that know their stuff too, I'm just voicing my personnel experience.
Tourer
Joined: Jul 2007
Posts: 497
Likes: 8
From: New Egypt, NJ
One thing about long strokes not discussed much is the "side load" on the cylinder when the crank is at mid stroke. A guy I used to go to the track with had a BAD *** Ironhead stroker. 4-3/4" T&O wheels, IIRC. Ran a 4"slick, was a HOT little street/strip bike. This thing blew the side of the front cylinder out and took the spigot and case with it during a run. The long rod/long stroke puts a lot of force perpendicular to the piston's direction of travel.
Now, case castings have come a LONG way since Ironhead days, but the longer strokes still push the pistons hard against the cylinder walls. This causes cylinder/piston wear more rapidly than in a lesser stroke engine.
That said, the 124" has been around for a while, now; it's not as if it ain't a proven combination... Just thinking about it in light of what I know about long arm strokers, it seems to me that an equally prepped 117 should outlast a 124.
Now, case castings have come a LONG way since Ironhead days, but the longer strokes still push the pistons hard against the cylinder walls. This causes cylinder/piston wear more rapidly than in a lesser stroke engine.
That said, the 124" has been around for a while, now; it's not as if it ain't a proven combination... Just thinking about it in light of what I know about long arm strokers, it seems to me that an equally prepped 117 should outlast a 124.