Factory 107" vs factory 114"

[biggzed]

Hey guys -

I am considering adding a Street Bob to the garage. Looking at used, not new. I notice the 2018 - 2020 bikes came factory with a 107". The 2021 has a 114".

How big a difference is there between the 107/114. I want this bike to be my rip around town/mountains/day rider. I still have my K1600 for the long hauls. Asked a different way, is it even worth considering a 107" now that they come standard with a 114"?

Also, I will likely add a CR480 cam and 2-1 pipe to anything I purchase. I see several dyno sheets in the Dyno section, but most are baggers. Is there a difference in throttle bodies from softail to bagger? Is it reasonable to expect similar results between the baggers and softail bikes? Not sure what other driveline differences may effect results.

Thanks,
Zach

[Deye76]

If 7 cu. in. didn't make a difference S&S wouldn't have produced a 117" and a 124". A 114" doesn't care if it's in a bagger or a softail, all things being equal they will spool the same on a dyno. 

[Don D]

I would not hesitate one bit. It is a big bore away from 124", a weekend job.

[Hossamania]

Given the option, I'd go 114. The 107 does well with a cam and a tune. The 114 does better.

[NHBagger]

If you can find a 107 bargain priced, you could bump it up and probably still not be at the price of a 114.

[FXDBI]

If you can find a 107 bargain priced, you could bump it up and probably still not be at the price of a 114.

Factory 114 is a stroked 107 not a bigger bore. Go for the 114 more potential.   Bob

[joes124]

If you can find a 107 bargain priced, you could bump it up and probably still not be at the price of a 114.

Factory 114 is a stroked 107 not a bigger bore. Go for the 114 more potential.   Bob

Exactly!

[mkriggen]

I'm going to go against the grain here. If I was looking to make an around town hot rodded bobber, I would go for the shorter stroked engine and bump it up to 124". It will wind up faster off the lights and your rings will love the slower piston speeds.

[sandrooney]

Go for the 114. Install some V&H Eliminator 300's, a PowerVision and leave the rest alone. They are awesome just the way they are.

[Hossamania]

So there seems to be a consensus: do it this way.
No wait, do it that way.
I do like the idea of the shorter stroke hotrod motor. And I like the idea of a longer stroke hammer.
It is fun to beat the bigger motors with a smaller one that's set up properly. Until one of those just waxes you, then, I need more!

[BigT]

I doubt the small difference in stroke from a 107" @ 4.375 and a 114" with a 4.5" stroke would have much effect on longevity of the motor, piston speed or the ability to spool up faster other than quicker because of the increased motor size.

[Ohio HD]

I'm going to go against the grain here. If I was looking to make an around town hot rodded bobber, I would go for the shorter stroked engine and bump it up to 124". It will wind up faster off the lights and your rings will love the slower piston speeds.

 

There's benefit to increases piston top surface area and the shorter stroke.

[Don D]

Agree 100% 

And a little more than a driveway swap is S&S 136 cubic inch. In a mild state of tune the result would exceed some very formidable twin cams. $3600 or thereabouts plus your choice of cam and other accessories.

[biggzed]

Great discussion guys. Thanks. I was being lazy and hadn't looked up the actual bore/stroke of each. My Dad has a 4.5" stroke twin cam. It had similar hp/tq to my 103" TC, but I felt like my 103" was much quicker (only proven a couple of times on some freeway on-ramps).

I like the idea of shorter stroke hot rod with option to go 124" easily/economically. It also looks like the CR480 would be a nice choice in 107" and 124" making it even more economical to upgrade to 124" after I get beat by a 114". LOL

Zach

[lonewolf]

114 responds to a cam much better than the 107.

[boooby1744]

Mod the 107 and lower gearing

[BigT]

I bought a 2017 107" Street Glide which is now 124" at a tad under 150hp. In stock form the  107" was a slug. Trying to pass a car seemed dangerously slow. As the saying goes there is no replacement for displacement. You can't go wrong with the larger 114" motor in my opinion. As far as the slightly shorter stroke spooling up faster that may be if the motor stays the same cubic inches. The 114" would spool right by the 107" in a race.

[VernDiesel]

Biggzed,  Throttle body options are the same. Softails do use internal balancers baggers don't. This is not a bad thing for a drag racing motor. Softails also weigh 110 ish pounds less than baggers. However baggers use longer pipes which improve torque and dyno numbers. Small advantage softail.
Nice torque plated 4.310 bore 4.375 stroke is still undersquare. 128ci

Retired pro stock Harley race engine builder George Bryce thinks (for drag racing) highest average horsepower for the shift to recovery range is fastest. For making power and keeping it his top three concerns; 1. Ring seal 2. Valve size 3. Bore.
Valve size and bore especially bore to stroke to fill the cylinder for ability to make power and ring seal to keep it.  Shorter stroke at the same rpm is a lower piston speed also less piston side loading both equal better ring seal. Less piston speed and better ring seal allow for more rpm.

Working with a pump premium motor that you are looking for reasonable life out of. You could spin a 4.375 stroke to 7k. A 4.500 stroke you might stick to 6,500 rpms. From 7k to 5,500 back to 7k you should see a better average horsepower than 6,500 to 5,000 back to 6,500. Cubes buy torque not horsepower.

If you are going into the shortblock where you are going to balance the crank and use better rods this advantage becomes greater. Unless valvetrain or other limitations come into play. Also you can bore the case to fit bigger cylinders. With new better aftermarket jugs available you can safely go to a 4.500 bore. This would make an oversquare 139ci that could spin breath & live. Albeit short block work is expensive.

We're already seeing 170WHP from pump gas builds. I don't know what a built liquid cooled 6 cylinder OHC K1600 can do. Certainly it has more potential than a simple 2 cylinder air cooled push rod motor. But I know stock the K1600 isn't seeing anywhere near 170 HP at the wheel. All this just my opinion. There are other factors that come into play this is just at the core. Engine builders here with far more experience and understanding than me. Most just won't teach and share a lot on an open forum.

[cheech]

Softails do use internal balancers baggers don't.

Not true!
All M8's are internally counterbalanced.
Touring have 1, Softails have 2.

[VernDiesel]

If that was the biggest mistake I made it was a good day. But I will fix it. 
Ack I can't apparently the forum only allows edits for a short period of time.

[sandrooney]

Softails do use internal balancers baggers don't.

Not true!
All M8's are internally counterbalanced.
Touring have 1, Softails have 2.

[Tynker]

Softails do use internal balancers baggers don't. T

Softails do use internal balancers baggers don't. T

Wrong. My 2017 107 Tri Glide balancer came loose and destroyed the motor. motor replaced under warranty.

[Hossamania]

Softails do use internal balancers baggers don't. T

Softails do use internal balancers baggers don't. T

Wrong. My 2017 107 Tri Glide balancer came loose and destroyed the motor. motor replaced under warranty.

As noted in response #18.

[biggzed]

Well I ended up deciding to sell my BMW K1600. It was a great bike, but after a lot of thought I admitted to myself frequent touring is not in the cards for me. Life happens when you have 2 teenage daughters. Getting out on multiple day rides several times a year just isn't reality anymore. I'm fine with it.

I got more than I paid for the BMW and immediately took that and bought a 2021 Street Bob with the 114". It's already got a Two Brothers 2-1, Saddlemen seat and a nice little fairing. I couldn't be happier to be an HD owner again.

Zach

[sandrooney]

Welcome back.

[Thermodyne]

The difference is more than just the 7 cubic inches.  The longer stroke on the 114 gives it an advantage over the 107.  More torque down low where the motors live.

[ziggy24]

I'm going to go against the grain here. If I was looking to make an around town hot rodded bobber, I would go for the shorter stroked engine and bump it up to 124". It will wind up faster off the lights and your rings will love the slower piston speeds.

Piston is speed difference is negligible between the two. It's a whopping 1/8 of an inch difference.

107"  3.937 bore, 4.375 stroke

114"  4.016 bore, 4.500 stroke

107 @ 5000 rpm =3646 ft per min

114 @ 5000 rpm =3750 per min

[VernDiesel]

I hear you Ziggy. Not a deal breaker either way but still some pros & cons to each. Depends on bike and bike use priorities but as said not a deal breaker either way.  Using your example I see that the 4.5 stroke has the same piston speed at 6,800 as the 4.375 has at 7k. But even at the same piston speed the 4.5 would put more side load on the piston and ring seal. Ring seal and a higher average horsepower from shift point to recovery means more to me than the torque advantage of the 4 ci between the 143ci (4.500 bore to 4.500 stroke) than the 139ci that I hope to build. (4.500 bore to 4.375 stroke) To 99% of riders who's priority would be the below 5k rpm use the 4.5 stroke would be a little better.  I should add this is what I think I know.  Always learning is a good thing.

To me this is some of the kind of tech I like to see discussed or debated in this forum.  Sometimes it seems like little actual tech talk happens on this forum anymore despite its original intent.  Some outstanding engine builders here some sort of newbs and some in between with limited tech discussion between the groups or even between skilled builders for all to benefit from.  That said to my knowledge it remains the best harley tech on the net.

[kd]

I'm going to go against the grain here. If I was looking to make an around town hot rodded bobber, I would go for the shorter stroked engine and bump it up to 124". It will wind up faster off the lights and your rings will love the slower piston speeds.

Piston is speed difference is negligible between the two. It's a whopping 1/8 of an inch difference.

107"  3.937 bore, 4.375 stroke

114"  4.016 bore, 4.500 stroke

107 @ 5000 rpm =3646 ft per min

114 @ 5000 rpm =3750 per min

Throw a gearing change into the mix of options.  Lowering the gear ratio in effect mirrors the way the piston ft per second changes.  It's still a time / distance calc.  Just in a different way.  It never seems to get mentioned then.   

[joes124]

KD,

Your gearing comment is spot on.

[Killer]

Jeez, you guys never change. It's been a year or more since I visited and this is why came back. Many different opinions and it all boils down to... gas,check oil and ride.