Building a 100 inch Sporty.

delcrossv · Aug 6, 2023

Oldest son expressed a desire to build a high output engine for his late model ('08) XLH. I used to do some sporty builds back in the 80's (mostly with shovelheads on sportster cases) so I thought, what the heck, let's give it a go.

Man, times have changed- S&S doesn't do stroker flywheels for sportsters anymore, and unless you have a 50 ton press, the cranks aren't serviceable anyway.

So Plan B- got a set for S&S "special application" cases with some shot 4" cylinders and some nice STD stage 3 , dual carb drag heads.

All cleaned up. Long studs will go as we're going with ductile cylinders.

All set for 4" bore.

Did a mockup with the old cylinders for grins.

We decided on magneto ignition so found a old school XLCH timing cover. The points drive is the same as a magneto drive. Going to trim off all the extra material outside the cam box. The cases will need some welding for the additional screws and the generator idler gear bushing.

Cylinders and pistons on order. More to come.

Fishinfool · Aug 6, 2023

Looking good. I am sure that Sporty will get up and go.

I bought a 883 Sportster back in 1991, I think, when they were $3995.00. The throttle seemed more like a sound rheostat - It got louder, but did not go much faster. That was OK, as I didn't plan on leaving it stock.

1200 jugs and pistons, higher compression, along with an S&S carb, some tuning and loud pipes. What a difference. Quicker than my buddies on their stock 80 inch big twins.

Larry

delcrossv · Aug 6, 2023

Heads:
As these were drag heads, there is no provision for oiling. The rockers were greased before each run. I do have a good spot to tap for an external drain and will have to go old school with external feeds to the rockerboxes too.

Intake is 2.09, exhaust is 1.75. The groove for the fire ring is 4.25 OD.

Triple valve springs.

I've been talking to Jesel about a lightweight valvetrain so I can reduce the spring pressure. Shooting for 8000 rpm redline, with an 8500 rpm overrev. Probably going to go with titanium valves and retainers to reduce sprung weight.

ladder13 · Aug 7, 2023

……following…….

Engineer1911 · Aug 7, 2023

Frightening what an Old Man with tools and knowledge can do to Milwaukee's finest. Squeeze firmly, twist, and hang-on!

Autonomous · Aug 7, 2023

That is gonna raise hell! I'm especially intrigued with the twin carb setup.

My first HD was a 1980 XLH with minimal engine mods.
The only one I did heads, bore, cams, etc. on was a Twin Cam Ultra.

1sailor · Aug 7, 2023

I've been riding Harleys for just a tad over 50 years now. I was never a big fan of the sporty's but I did once own a K model. It was the flathead forerunner of the Sportster. They have come a long way since they first came out. Motors getting bigger and also the introduction of rubber mounted engines. I'd be willing to bet they can be made to scream with the right mods. Your project looks to be quite a bit more complex than your average "build".

delcrossv · Aug 7, 2023

Update: The stock 1.25" crankpin has a tendency to flex under high load making the flywheels spread.
Stock pin:

This leads to broken pinion shafts. HD's solution on the XR engines was to go with a 1.5" pin like this:

So far so good, but the XR pin is not presently available and took a narrow 1.35" rod set. Carrillo can't make these as the narrow female rod races tend to separate from the rod ends

Badness.

So I was able to find this pin from S&S (new old stock)that's Sportster length, takes a full width 1.49" rod set and is 1.500 in diameter. Drive side is welded, timing side is tapered. Nice and stiff.

Seeing how Carrillo is making the rods to order anyway, the only additional pieces I need to have custom made are the roller cages.

Yay!

Autonomous · Aug 7, 2023

This is giving me the strangest *****.

Keep it coming!

1sailor · Aug 7, 2023

I'm going to guess here that you have a lot of equipment that is not commonly found in most garages. I've never known anyone who made their own bearing cages. I'm impressed.

delcrossv · Aug 7, 2023

1sailor said:
I'm going to guess here that you have a lot of equipment that is not commonly found in most garages. I've never known anyone who made their own bearing cages. I'm impressed.

Oh, not me. That'd be a CNC job. I should have said "have made".

Making one by hand would be a whole 'nother level of tedium.

Fixed. Thank you.

Should be cost effective as it's a Carrillo nitro rod cage, just narrowed to sportster width.

1sailor · Aug 7, 2023

You know, in all the years I've been riding and hanging out with other bikers, I have never heard one ever say "cost effective" before. I didn't even know those two words could fit together. At least not when talking about custom builds.

Marshwheeling · Aug 7, 2023

Not much of a Harley fan here, but this one holds a strong fascination. Calls to mind Steve Hamel’s Vincent work.

delcrossv · Aug 7, 2023

1sailor said:
You know, in all the years I've been riding and hanging out with other bikers, I have never heard one ever say "cost effective" before. I didn't even know those two words could fit together. At least not when talking about custom builds.

LOL. Must be the engineer leaking through.

S&W Fan · Aug 7, 2023

Very cool. The last Sporty I had was a 2006 XL1200R, the last of the carbed versions. I did suspension upgrades on it and had it "breathed" on by a now closed shop fairly close to me. Loved smoking the baggers (even though I eventually went back to one haha) that would look down on our "girls bikes". It dyno'd at 94hp with 97 ft lbs of torque at the rear wheel.

Sold it when I came across a really killer deal on a '14 Fat Bob.

With the original a/c cover on it

I called it Mr. Bob lol, 121ci

1sailor · Aug 8, 2023

Well since we're talking bikes and posting some pics I'm posting a pic of mine. I first built it in 1992 starting with a 1982 FLH frame that was cut and stretched to accept a Softail tranny and Evo style motor. Over the last 31 years I have traveled 11 states and crossed the Continental Divide multiple times. Happily, I was able to travel a lot of those miles with my son. I also built his bike. As it currently sits it has a 120 inch motor with a Baker DD6 tranny. When I built it my intention was to build a bike with a "classic look" but not a replica of any particular model. I also adapted an Indian teardrop headlight just to make it a little different.

delcrossv · Aug 8, 2023

1sailor said:
Well since we're talking bikes and posting some pics I'm posting a pic of mine. I first built it in 1992 starting with a 1982 FLH frame that was cut and stretched to accept a Softail tranny and Evo style motor. Over the last 31 years I have traveled 11 states and crossed the Continental Divide multiple times. Happily, I was able to travel a lot of those miles with my son. I also built his bike. As it currently sits it has a 120 inch motor with a Baker DD6 tranny. When I built it my intention was to build a bike with a "classic look" but not a replica of any particular model. I also adapted an Indian teardrop headlight just to make it a little different.

That's a looker for sure.

1sailor · Aug 8, 2023

Thank you.

delcrossv · Aug 8, 2023

Rods ordered from Carrillo (after many false starts)

**Plus changes: Center to Center length 7.440"
Sportster XR750 : ***Plus changes
***Center to center : 7.440"
***Pin End Width : 1.081" (.050" clearance per side)
Pin Diameter: .791"
Female Big End Width : 1.490".
Male Big End Width: .560"
Big End Bore : 1.877" semi finished

The longer rods give a 1.86 rod to stroke ratio which is pretty much in the sweet spot at close to 2 to 1.

So a longer XR 750 rod with an H beam, instead of an I beam, with a wider big end and standard XL diameter rollers. 21 instead of 16 like a normal XL.
All about compromises. Glad that's done!

Mike0251 · Aug 8, 2023

Looking good so far! I had a 1957 sportster for 25 years. All stock except for my engine. 4 5/8 stroke, .020 over, S&S L series carb, Andrews close ratio gears, Andrews cam, ported polished heads w/stainless valves and bronze guides, Trock billet trap door (a must!), and Barnett slipper clutch. I also obtained another cam gear cover, removed the 4 bronze bushings for the cams and replaced with Torrington needle bearings (exact same as whats in the case half and they fit the bores perfectly too). Machined off the bushing part and kept the head for spacers and then shimmed accordingly. When I would take it to the 1/8 mile drags I added wheelie bars, racing slick, and an air shifter. Best time was 7.02 @ 98mph.

I tried a belt drive for awhile until a holeshot ripped every tooth off the belt LOL. Went back to chain. I also used to rebuild many older engines for several years, FH, PH, SH. I assume you still have to true your flywheels? Had a truing stand and was very good at it. It's an art.

Best of luck, keep us posted!

Building a 100 inch Sporty.

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