Hammer 1250 Conversion vs. Big Twin (w/Intake & Cams): Who Wins?

[DrSpencer]

I've had many Big twins, stock & modded, so I'm familiar with their different levels of power delivery.

I now have a 2017 Iron 883 that I'm considering converting, using a hammer 1250/1275 kit.

The stock 883 is pretty underwhelming. Exactly how fast is the Hammer 1250 when compared to a 103 with Stage I, cams, pipes, and a good tune?

I'm interested in the performance comparison between 0-90MPH. Not concerned about top end, or the 5-speed vs. 6-speed debate.

Thanks

[rigidthumper]

It's all about power to weight- Very few Big Twins will take a properly built XL. Pauls, for sure, maybe 1 or 2 others. A stage 1 103? Not even close, it would be close to a stage 1 883
Stage 1 103 FLHX makes 85 HP, and weighs 810, so 9.53 pounds /HP
Stage 1 XL883   makes 55 HP, and weighs 562, so 10.21 pounds /HP
Fairly close, and the lighter weight bike "should" have better acceleration, less mass to get going. Both will run mid 13s in the quarter.
Hammer 120+HP kit would be less than 5 pounds /HP,  and will run sub 10 seconds 1/4 mile times with a good rider.

If you want real fun, S&S sells a 100" sportster engine

[aswracing]

There are a lot of things that drive how quick a bike is. But probably the most fundamental is the power-to-weight ratio. So look at power and weight carefully. It's not the total answer, but it's the majority of it.

With respect to a 1250/1275 conversion on an 883, this chart pretty much describes the range of what can be done ...



In blue is a full-boogey 1275 conversion with top of the line head work, cams, and larger throttle body.
In red is a basic 1250 conversion with a pipe and air cleaner and tuner only. Still has stock heads and cams and throttle body.
In green is a bone stock EFI 883.
All three of these results are the same bike tested on the same dyno.

So that's kind of the range of what can be done.

HD lists the running weight of a 2017 Iron at 562lbs. Therefore you have ...

4.2lbs per hp for the full-boogey conversion
7.2lbs per hp for the basic 1250 conversion
12.2lbs per hp for the stock 883

Now, for the 103 Big Twin, let's pick a relatively lightweight one. HD says a 2017 Dyna Low Rider weighs 666lbs in running order.

To match the 7.2lbs per hp of the basic 1250 conversion, you'd need to pull 666/7.2 = 92.5hp . That's a pretty easy mark for a 103 with stage 1 mods and cams.

If you're talking about a dresser, of course the answer would be different. Likewise if you were talking about a stage 1 103 without cams, the answer would be different. And if you're talking about more mods beyond just the basic 1250 conversion to the 883, the answer would be different.

But answering the question in the way you posed it, and assuming a Dyna, I'd give the advantage to the 103.

[Carl 1969]

Power to weight ratio leans heavily (i know...) toward the Sporty & even a mild 1200 Sportster is going to embarrass even "built" Big Twins.

As an example, my old '94 883/1200 put down 73hp/79tq & the only Harleys in town that could leave me were a tweaked out 1200 XL putting down right at 100hp & a 97" S&S Softail. There was another dude with a full-tilt 80" Evo in a Kenny Boyce frame that could stay with me, light to light, in town.

Doing the math, it would take ~95hp/105tq in my '02 FXD to equal the power to weight ratio of my old Sportster & it'll cost a good chunk more to take my TC88 to that level than I had in that Sporty.

[boatdoc]

Hey DrSpencer my wife has a 1250 Hammer conversion on her sporty. A mid level build with cams and ported heads. I have a bagger with a 124, Hammer built.
These two bikes run neck to neck. No way will a mild 103 keep up 0-90 mph. Not even close.
Aaron and Dan at Hammer Performance are good to work with and will set you up with a great 1250-1275!

[DrSpencer]

Hey DrSpencer my wife has a 1250 Hammer conversion on her sporty. A mid level build with cams and ported heads. I have a bagger with a 124, Hammer built.
These two bikes run neck to neck. No way will a mild 103 keep up 0-90 mph. Not even close.
Aaron and Dan at Hammer Performance are good to work with and will set you up with a great 1250-1275!

Good to know.

How is your wife's Sportsters street manners?  Does it handle stop & go city traffic very well? Or is it high strung, always wanting to run?

How much additional heat should be expected?

Thanks

[Ohio HD]

Keep in mind, all 103's and all 124's aren't equal. I might listen to what aswracing is saying, since they build them.

[boatdoc]

DrSpencer my wife's bike is very well manered, handles city traffic,stop and go no problem. The clutch pull is easy. No extra heat, oil temps never even get to 200 .
Total no pms build. Aaron dyno tuned both bikes, sportster is 90 square, but the torque is in early and smooth and it revs out well.

[Carl 1969]

A Sportster that goes 90 square is going to embarrass the hell out of the vast majority of big twins you'll run across.

[72fl]

A Sportster that goes 90 square is going to embarrass the hell out of the vast majority of big twins you'll run across.

ABSOLUTELY CARL!!!!!!!! They run like a striped ass ape buddy had one it would put a hurt on the Crotch Rockets 

[speed limit]

My wife has a complete hammer crush level kit 110hp + although it will run circles around my stage 1 103 RG, its no match for my 127 RK

[Thakery]

I have a Hammer 1250 conversion to a 2006 xl1200r and am about to go with their 560 cams and port the head (somewhere else in England ! )... it is good fun and I have geared it up with a 32 trans pulley. I also have 2010 Streetbob which is out to 113" (CVO heads and cylinders with 11.5:1 static, S&S 640 cams etc etc ...) and pulls 127bhp and 121ftlbs on a carb.... the sporty is more fun to throw around, but the streetbob has the legs on it and is way more comfortable on any journey of 50+ miles. I am 58 so maybe I need comfort, but what are you gonna use if for - playing around in town or freeway work......