Well it has been a few months since I've been on here last time I was on here everyone was telling me go 107 over a 103 now I'm on here looking around and I'm seeing most people are telling others to stay with a 103 and just do headwork and cams. So my question is what so I want to honestly do I'll probably have the bike another 2-3 years and I want to be able to have some fun on it. Would like to have around 115/120 on hp and tq. I ride upper rpms when with the buddies but also just cruise around in lower rpms. I'm at 86/104 right now 2015 SGS with SE ventilator, FM 2-1-2, SERT. I will be doing all assembly of the motor myself. Yes I am capable of doing it myself.
OR do I just get a HD 110 drop in kit and return the hd parts I don't need and just keep the jugs and pistons? buy my own cams and what not to go with it???

HELPPPP

 

Figure about 1.05 hp per cubic inch, for a well built twin cam. To get there, you need about 10.2 or better compression, good flowing exhaust, medium duration cams, ported or aftermarket heads, and enough fuel. Look for combinations that have been proven out already. If you want 115 hp, I'd go no smaller than 110.


The difference between a 103 and a 107 (assuming all other factors are comparable) is going to be about 4 hp, give or take a little. Adding displacement will increase hp and torque across the board, but bumping up 4 cubic inches is a modest increase, which will return a modest gain.


You can bump compression to increase gains, but going past 10.5 compression generally will mean a hotter running motor, and won't be as enjoyable on a long hot summer ride. I like big displacement, lower compression motors for touring bikes. I've been collecting parts for my next build. I'm shooting for a 120 hp 113.

 

Thos are exactly the numbers that FuelMoto got for me with their 107BB/777s/SE Throttle Body and 49mm jets. /L2 Heads and 10.5:1 comp with a V&H Propipe.

(Oops, maybe you meant 120hp/113cu in)

 

Try googling. Think there is a few VS threads on this.

 

115hp is a tall order using stock 103 pistons (I'm getting 112). If swapping to high compression pistons might as well go 107. Jury is still out on 110 bolt-on jugs...

 

103 vs 107 is like 7" vs 7.25". It takes a trained professional to feel the difference.

It's mainly the compression difference making the extra hp. I would call Hillside and talk to them.

 

I just bumped my motor up from an 88 to a 103, SE MVA heads, 10:1 compression, 255 cams, 58mm throttlebody and intake, SE flywheel, it did 117hp and 111 tq with true duals , I'm having a 2 into 1 pipe made to bump up the torque. The bike gets up and goes!

Everyone (who have actual experience with the kit) I talked to about the 110 kit said not to go in that direction. I couldnt tell you why but it universally got the thumbs down. take that for what it's worth. best of luck!

 

Save yourself effort and agony and just call one of our HDF sponsors, of whom we have several, who can advise you and provide a proven package of parts. You'll get more performance from a bespoke tuning package than H-D IMHO. Hillside and FM come to mind.

 

You can get close to your numbers with the 110" drop in kit with the right cams and exhaust; seeing more and more of those sheets with good numbers and curves. Have seen several sheets of the Stage V "Tire Shredder" kit with 125/125 numbers hitting 100TQ about 2200-2500 rpms. Maybe a bit pricey at $2600 plus labor and tune (no download, please) for the kit but it's basically a top end rebuild.......................

If that doesn't float your boat, stick with the 103"er, good headwork, cams and exhaust and the 103"er will be a runner but not a 125/125 runner.

 

GRBrown nailed it. Best call a respected builder and get it right.