Has anyone ever bored out a 1000cc Ironhead? And if so, what is the max displacement that can be achieved on this engine?

 

There's really not enough meat in the cylinder walls to achieve any practical increase by boring. You can stroke the engine and take it up in size. My '72 CH was stroked to 77 inches, and with the hot cams, head work, and bigger carb, ran like a scalded dog. I also spent all my spare time working on it.

There are big bore /stroker kits available, too. I've seen a 118 inch Sporty, but it wasn't something that I'd call streetable. Biggest street Ironhead I remember was an 89 incher. He worked on it more than he rode it. Everything was stressed way past design and things had a habit of breaking.

When you put a big bore kit on an Ironhead, you usually have to fly-cut the spigot holes in the cases to allow the cylinders to fit. Too big and the cases are weakened too much. Next step is to build up around the spigots and then redeck them for some added strength. Stroking can get crazy, too. To get the big inches the stroke has to get pretty long. That increases piston speed and that means more wear on cylinder walls and pistons. Plus stroker pistons often have to have shorter skirts in order to clear the flywheels and so they tend to rock in the cylinders meaning more wear, again.

You can also get into all the extras - stroker plates under the cylinders to allow for increased piston travel, new top motor mounts because the engine is taller, new intake manifold because the cylinders are further apart at the top, longer pushrods, ...

If you are seriously interested in a big inch Ironhead there are a few excellent sources. It's best to get a complete kit from one source, and also have them do any machine work needed. I'll see if I can scrounge up a couple addresses and get back to post them.

 

Here's a link to S&S. They have kits for Ironheads in 72" & 74" sizes.

http://www.sscycle.com/catalog16/pg/...ster_Buell.htm

Used to be an outfit named "Stroicek" (I think) that made high perf Sporty parts, but my searches are coming up empty.

 

So it appears that it would probably be more trouble then it is worth. Out of curiousity, how fast would a 100+ CI sporty potentially be? What kind of speed did you get out of your 77CI build?

 

The 100+ inchers I remember were running in the 9s at the strip. This was back in the '70s, though. My 77 inch would run over 135 mph on the top. At least that's what the Illinois trooper said we were doing. It was a pretty wild ride as the rigid frame was too flexible for the power. I had a lot of frame cracks to repair at the end of the summer. On a hard launch I could see the frame twisting below and behind the seat.

I don't know what it'd do in the 1/4 mile, but I used to run it against Japanese bikes in street races. It'd do pretty good; I could wipe the near stock 750 types, and could usually beat my buddy's 900cc (big bore 750) Honda, and even had a chance against the old Kaw Z-1. It was a lot of fun because everyone "knew" HDs were dogs, and to someone who didn't know what a Sporty was s'posed to sound like, they'd not guess the bike was stroked.

The rear tire would last 2 or 3 weeks if I was racing on Saturday nights, and maybe 2 months if I was relatively well-behaved. Chains lasted about half the summer. Clutch packs didn't last too long, either. I blew the trapdoor on the tranny into a couple million chunks when I dumped the clutch once. Also had the tranny let loose when I missed a shift. One of my buds dumped the clutch on his XLH with the front wheel against a brick wall. He hit second gear in a big cloud of smoke, and then we heard a loud boom-clunk, and the bike quit. He grenaded the trapdoor, blew the rear corner out of the cases, and had so many cracks in the engine area that we were surprised they could be salvaged.

Anyway, I was young, stupid, and it was tons of fun. Today I travel a wee bit slower. Figger I had my run of luck, and my bones remind me of it every weather-change.

I think the S&S 74" kit, if used with low comp pistons, would be a good engine. But stock, or near stock, Ironheads are getting scarce. If I had one that was trashed I'd probably build it up. For one in relatively good shape, I'd probably keep it near stock, or at least do nothing to it that couldn't be "undone" at a later date.

 

Well the stock bikes of this model seem to top out at 115 mph which is fast enough for now. I will wait until I rebuild the engine before I make any serious mods. I was just curious how much can be done to these engines and if it was possible to build them over 100ci. I think a sportster with a 100ci engine would absolutly rock. But not yet. LOL

 

had mine bored and stroked and it's a 1242 now

 

I have a 77 XLH 1000 that took me 3 1/2 years too rebuild. With the fresh overbore pistons it's a whopping 62" engine. S&S Super E, P cams, Paughco Drag Pipes with baffles and a Dyna S dual fire ignition. 16" rear wheel and a 23 tooth sprocket. My Wife has a 2004 XLH 1200 Custom, Dynatek Ignition, re-jetted CV_40 and V&H slip-on mufflers. When we ride together, my Lil 62" keeps up with her till she hits 5th gear. So my advice to you is KISS. Keep It Simple Stupid. Just rebuild it with QUALITY parts, NOS are best and no V-Twin (aka Tiawan Ted) or other manufactures that use that rare Chineseium metal. All I can say is ride it the more you stress the engine (stroker kits, big bore that involved massive $$$ machine work) the more problems you will make for yourself . . . and LOOSE RELIABILITY.

 

Google "Shovester". Old school way to increase displacement on a Sportster, but definitely requires some machine work.

 

I had a 1979 that I had stroked to ~74". It was a blast to ride! The power was very satisfying! Fooled some Big Twins in roll-on's. The brakes and suspension were lacking, but that added torque was.......... yummy!