OK, chiming in here because I have a Sportster engine, rubbermount engine just like the newest Sportsters but mine is a '97. With about 105hp at the crank right now (91 stock), a genuine 150mph bike.
A Buell S3:
http://www.motorcyclespecs.co.za/model/buell/buell_s3_thunderbolt.htmWhat I like about it: from a chassis/suspension point of view, there's nothing better. Literally. It's Ducati-grade stuff in every way.
The motor is the same as a Sportster except "pumped up" from the factory.
It is stone-axe primitive: aircooled, two valve per cylinder, pushrods, etc.
But all that said, here's what's RIGHT about it.
It's overbuilt...tougher than it needs to be. It can be disassembled and rebuilt by any idiot with a basic set of wrenches. The valvetrain is hydraulic, which means they never need adjusting. High-strung sportbikes need their valves tweaked as often as every 5,000 miles - less in the case of Ducatis. And the process is ugly on the Japanese bikes, downright hideous on Ducatis...doing your own valve adjust on a Jap sportbike is barely possible if you're GOOD, impossible on a Duc.
The power delivery is smooth and strong, but not "peaky" like a hyperactive Jap 600. I'm making as much power as most of them, at half the RPM and with a powerband twice as wide.
Even though the engine's bottom end and transmission are in the same block of metal in a Sportster, the oil pools are separate so each gets the right type of oil. Japanese practice is to run one pool of oil for both and then use oil that's a compromise between the two needs.
The Sportster bottom end and tranny are tough as nails and are unlikely to break. The top end CAN but it's pretty tough too.
That's not to say you can do stupid stuff.
Example: when I bought my Buell about six months ago, it came with a super-high-flow air intake (Forcewinder) on the stock carb, and only about 4,000 miles on it. I asked the seller whether or not the carb had been re-tuned for that intake and moderately good Yoshimura exhaust can, he said "yes". Silly me, I believed him...should have had it metered and checked.
So about 1,500 miles later at 80mph down the freeway on a hot day, the lean-out condition got wild enough to burn a hole in the front piston.
Sigh. The good news was, I got the bike at a real good price so I wasn't TOO screwed.
A bit of research later, I started ordering parts. I decided if I was going to tear it all down, I'd build it up right, basically replaced the barrels, pistons, rings, heads and while I was at it, put in a good Mikuni carb to replace that stock CV type.
Two weeks after placing that order (about $2,500 [WAIT, on edit the bill was $2900] worth of go-fast bits) I didn't just have the parts, I had the bike back together and running strong...doing all the wrenching myself and this was the third engine I'd ever rebuilt to this degree myself...none prior were Harleys of any sort.
This is NOT possible on a japbike.
Why $2900?
Instead of a 1200, I now have a 1250 - with ceramic-lined barrels, 10.5:1 compression forged race pistons with the 1998-era dome pattern, with 2004-spec bigger-valve heads with better port flow re-cut to the domed pistons (very hot setup), special adapter to let the 2004 heads work on the '97 frame.
The only way I could have gone hotter is with the 1450cc cylinder/piston kit but that means machining the original cases. The 1250 kit is a drop-in.
Now.
You want a hot Sportster?
Here's what you do:
Find an old 883 Sporty in good shape, mostly stock. 5speed tranny if possible but the 4sp ain't bad. Maybe one so old it's chain-drive, but still Evolution instead of "Ironhead". 18" rear rim versus 16" if at all possible...better handling potential.
First just ride it a while. Do minor mods to the suspension: fork brace, better rear shocks if you can find some at a good price (stock won't be too bad unless it's a "hugger", avoid those at all cost). Put steel-braided front brake lines in, and swap handlebars to something more "Cafe". Then dig around for a used set of "rearset" foot pegs, check the various sportster forums esp.
http://xlforum.net/index.html - check the "cafe" subforum there, see what other people are building.
While the motor is still mild, learn to ride this thing right. Follow some friends who know what they're doing on sportbikes, follow them around the twisties and track their lines. Work up slow, feel what the frame is telling you as you push it.
Now you're ready to get cookin'.
You wanted to start with the 883 because while the motor's bottom end is the same as a 1200 (or my Buell for that matter) the 883's flywheel is lighter. It has more go-fast potential than the 1200.
Shop here, these guys rock:
http://www.nrhsperformance.com/At a minimum, you want a 1250 barrel/piston kit with the Axtell Nikasil barrels and forged pistons - about $1200. You can order them set up for 883 heads and the results won't be too bad (your heads will need minor local machining or send them in to NRHS for matching to the barrels/pistons), but for best results get new heads to match. I went with stage 1 2004-spec.
But let's remember, my Buell already had good cams. You might get a more cost-effective boost with your existing heads and some wilder cams - talk to NRHS. I also strongly recommend the Mikuni 42 carb.
Running your stock heads, you could come in under $2,000. What you'll get will be both way hotter and tougher than stock.
It'll also be cheap to insure and will be a "sleeper" from hell
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