Just can't get the notion of an Ironhead custom out of my noggin. Those motors just sound so unique...

...anyway, I found a running late model Ironhead XLH 1000, and the guy is asking $2,500 which means he'll take $2,000... now, that is. If I get lucky and nobody bites for a few months and I got it for, say, $1,000, I'd have a reasonable justification to plunge into this project. Problem is, as usual, the bike is two days' drive in both directions, so we're talking either three hotel rooms and a bunch of diesel for my neighbor's truck, or an el cheapo, open trailer shipper--not ideal, even though this PO will send a cold start video and receipts, and scan of the clear title. But either way I'd be paying closer to $2,000 for the bike. Bummer. Really wish I could find one cheap here in NM, CO, or TX...

That said, I'd get a tight engine and tranny with L/H shift (not critical but fine with me), dual disc fork and rear disc setup if I wanted to transplant those, etc.

In ether case, though, as Architect suggested, the shortest straight route to dual carbs without messing about with the engine internally would be to weld up my own custom manifolds and (for instance) fit dual Dellorto PHM 40mm carbs--the R/H one tucked in tight inside my thigh, the L/H also tucked in tight but aimed forward, air horns with mesh screwed onto the carb's throats rather than bulky air filters--though K&N does sell pretty tiny cones. I could always shove foam 'socks' over the mesh trumpets to get off the dirt easement and onto the blacktop...

The Dellorto 40s typically come jetted for a 1,000cc Ducati, so should be in the ball park for a 1,000cc Sporty--or at least a decent starting point to begin futzing with jetting without burning an exhaust valve. With the Dellorto's accelerator pumps, she'd be thirsty (the record-setting, aluminum-jugged Sporty shown earlier had the pumps blocked off 'for gas mileage'), but I'll bet my envisioned bike would a real stop light ripper--and with a raucous, unique sound.

As for a still emergent design aesthetic, I've posted about the first exemplar below elsewhere--a familiar but clean look using a readily-available aftermarket frame. However, the second is another neat potential direction (not sure about the frame...just a bolt-on rear hoop to convert a stock early Sporty to rigid?). The tank's lines appeal to my eye due to the vintage flat track style (the saddle would have to shift backward a bit to accommodate my 34" inseam...). Though I do have a 'turtle' Sporty tank in the garage...

Whichever direction I went, I like the idea of aluminum rims to further lighten her up for quicker acceleration off the line. Recently laced up a pair of Borranis for the '71 custom Bonny cafe bike I'm finally about to finish up, and they were surprisingly easy to work with--though I let a local shop mount the tires to avoid scratching them up (3rd pic).

 

Two Rear Heads..not difficult, and has to have dual carbs...BTDT
Ron Trock SR (The Originator of the concept) called it X-Head!!!
Edit; I guess I do Not recall why not two front heads??? But..Ron was Specific!
I suspect whatever yer Stash bears out!!!

 

Super cool thread. It does get your mind wondering and thinking “I can do that”… then reality says… yep, just totally empty your wallet and look forward to a L O N G build. Cause every time your stumped it will sit for long periods. At the end of the day you’ll have something cool and unique that’s worth almost as much as stock. I’d find one done and re-do it just to save money and time.

Anyway.. regardless of how awesome this thread is the real question is how in heck did they get this bike to 166 lbs? That’s just not possible. Are the forks, frame, swing arm titanium… heck the tries with air even on aluminum rims and hub would be 75-80 lbs. They call them IRON heads for a reason and iron is heavy????

 

Your points taken in reverse:

First, yeah, no way the bike was 166 lbs. Perhaps they mean the engine weighed 166 lbs, as both the cylinders and heads are aluminum--custom made by the owners/racers. So, aluminum heads, cylinders, pistons, and cases, it's conceivable that with steel crank, rods, valve gear, and tranny--and leaving off the carb, manifold, and generator--they netted 166 lbs for the power plant itself...?

Second, glad my wacky idea appeals to someone else--and too bad those of us who like this kind of stuff don't have a brick-and-mortar clubhouse to drink coffee and barbecue in the driveway, help wrench on each other's bikes, and churn out some really cool stuff for each other. Can you imagine the club rides? What a spectacle!

Edit: a suggested name for the club might be "Evil Twins," so any pushrod-operated twin-cylinder bike might be eligible to join...? Or just pre-Evo Harleys? Or...?

But I digress... it'd be great if I could find something that someone had headed in the right direction but that seems unlikely. As for money, I recently retired very modestly, so I meant what I said above: the single most significant step in committing to this build is finding a solid donor bike for a great price (and any tips on candidates are hugely appreciated). I hadn't considered the later model Ironheads but have realized upon some more reading that they may be ideal re: my particular criteria.

Finally: it does add weight to have an electric start, but unless I get unbelievably lucky and find a tight, kick-only XLCH for pennies on the dollar, the production figures suggest the odds are far greater that a solid, cheap Ironhead will be a later model. And, frankly, I won't mind pushing a button. I can always scratch my mule-kicking itch with the 74" '51 FL...

 

So, straighten me out if my mind's eye gets confused here, but two rear heads would have both carbs aimed forward, while two front heads would have the carbs aimed aft... right?

In the first scenario, you get one exhaust pipe passing close(ish) to one intake runner; same with the latter scenario, as pictured in an earlier post of the Japanese bike. I guess that--in addition to cost and not having to figure out cam and ignition timing issues--is why I was wondering about leaving the cylinders in their OEM configuration and fabricating custom intake manifolds, both facing forward.

However, somebody earlier wondered about swapping the heads: "What if you were to run a front jug installed as the #2 jug, and the rear jug installed as the #1 jug? Wouldn't that make sense if you wanted two carbs so both carbs would be on the outer sides?"

That would indeed put the rear carb aiming aft--and some creative oil tank/battery location work could essentially have the rear carb entirely out of the way, The problem is that the front carb would be extending forward through the downtubes--kind of unappealing aesthetically, to me. Or I suppose it could sort of nestle in there and maybe aim to the R/H side with a curving custom manifold? That might not look too bad--and the overall narrowness of the Sporty V-twin could be largely maintained (I do not like a carb jutting into my knee--the test rider's major gripe about the aluminum super Sporty below).

If the front carb issue could be solved elegantly--and assuming one could figure out the cam timing issues--the really cool thing about just swapping the heads that then asserts itself is the exhaust. The most natural solution indicated by two ports aiming down and toward each other would be a two-into-one header, which nicely done and chromed could be really cool--but one could also bend up a really neat-looking side-by-side dual exhaust that either swept back just above the ignition cover, or described a J-turn around it and then back.

 

The Trock two rear heads have the rear head on the front Turned 90 degrees.. Hence "X-Head" ...no need to disturb cams...as we had some rather expensive Zippers Cams.. Easy and Relatively Inexpensive conversion.. Thanks Ron (RIP)
Two Notes.. the Front Rocker Cover needs a Bit of Enlargement/clearance-ing of two bolt holes.. more if using Later Model Iron Head stuff. and the Machining of head for Pushrod (tube) clearance is Daunting to some!!
Finally..Be careful of Carb selection...we Ran a Pair of 44mm Mikuni (round Slide back then) and you needed some serious forearm, grip, strength, to compress two of those Slide Springs...especially since I used an 1/8 turn Throttle!!

Edit; Our biggest cost was duplicating the "headwork" on a third Head..

 

I'm sure this is just my inability to visualize properly, but if you turn a head 90 degrees, how do the pushrods engage the valve gear? I just can't wrap my mind around this...

As for the cams, is the implication that the lift and duration on the Sporty's intake and exhaust lobes are identical? But assuming that's the case, I guess I'm having trouble understanding why the timing wouldn't be off--and please understand I'm not challenging your knowledge; this is likely just my own ignorance driving my confusion.

It seems like with a rear head fitted to the front cylinder, the exhaust valve would be operated by the front intake cam and what is now the intake valve operated by the front exhaust cam, so why wouldn't the compression stroke and firing be all wrong? Is the explanation related somehow to the 360 degree crank and wasted spark ignition...? Sorry if I'm just slow on the uptake, here--but I really want to understand this, so I can consider all straightforward, less-expensive options.

The machining you describe is not an issue, as my neighbor does the custom work to churn out the bespoke parts I design for Creative Spridgets, as well as the custom DIY front disc brake caliper adapter I designed for the '71 Bonny pictured below and in the attached photo (before I went with the vintage-style aluminum fairing, DIY rear-sets, and clip-ons you saw earlier). He owes me some time on the CNC mill, and will let me use his Bridgeport, which is usually gathering dust...

On the springs--thanks for the heads up. I have not ridden a bike with Dellortos, but the early Beemers as well as Ducatis had them, and I don't think I've read that the returns are too heavy. At any rate, I could always change out or modify return springs on the Dellortos--which are looking like the single biggest expense on this build aside from the donor bike and aluminum rims if I go that route (they could always wait their turn per budget considerations).

 

Visualize... or grab an excess head.. take rear head, place on front turned around 90 degrees.. both Intakes now pointing toward each other forming the "X". Exhaust still out front but, at other side.. now..place the Rocker Box on...conventionally...see how it will drop right On!!! If you have an Ironhead laying about..Pop Rocker on...either Way...see?? All ya Need is said clearancing of Box, and removal of Finns to facilitate Pushrods..
I have a Picture someplace.. but. Not at Home just now.. Cams are Now a Non Issue..

 

To use two front heads, the cams for the rear cylinder would need to be specially ground to your specifications so the instake timing is correct for the new location etc. Leineweber cams can do that. I don't recall any reason the front head wouldn't bolt up to the rear cylinder on an Iron Sporty. Been a very long time since I've had heads off an Iron Sportster. Does anyone know that it won't work?

Two examples, but not Iron Sportsters. A Shovel and a Panhead, so just one can is involved. A good friend, the guy pictured, build both bikes frame up including the machine work on the heads and in this case, the cylinders since the bolt pattern is different between front and rear. He is on Instagram and both bikes are featured with some pictures showing the work involved in making this work.





Paul

 

I needed this part to get it… you’re making too much sense and I don’t wanna start looking for a iron head.