Want $2000 Bucks off a 1200cc Sportster?
By Dave Murray
The engine roared? No, that's not strong enough. The sound of the (now) 74 cubic inch Sporty's politically incorrect straight pipes inside four concrete walls, even wearing earmuffs, was a pummeling, physical force. Sorta like the one-oh-fives when you have to call them in close. It fell off to merely deafening, and then Geoff again rapped the throttle to the stop for the third dyno run. He looked at the CRT for a moment, three identical curves atop one another, shut down the engine and turned to me grinning: "Don't change anything!" The readings? Tell you in a minute.
Did you know that you could have a really quick 1200 Sportster for two thousand dollars less than the Motor Company demands? The trick is, don't buy a 1200. Get an 883 and breathe on it a bit. We're talkin' American Iron here, so I'm gonna use honest to God Cubic Inches from here on out 883 cc= 54 cid, 1200 cc= 74 cid.
The last time I checked, the HD new price delta between the 54 and 74 Sportster was three grand, depending on bells and whistles. Here's the kicker. You can convert a 54 to a 74 for a thousand dollars, mas o menos, including labor! The only difference between a stock 54 and 74 is the bore, 3 inch instead of 3.5 inch. (Actually, the stock Sportster 74 uses a modified head with slightly larger chamber volume and bigger valves, but there's a way around that.)
You can do this (at least) three ways:
1. Have the dealer do the work, using stock 74 cid HD pistons, cylinders, and heads. This is a bit more expensive, but you keep your warranty (if that is a concern).
2. You, your H-D dealer, or an independent shop can do the switch, using stock H-D pistons and cylinders, but modifying the existing 54 cid head. I didn't much like this option, particularly as you have to figure hours of honing the cylinders to fit the pistons. This is skilled work. Screw it up, and you've made expensive junk.
3. You or your favorite wrench can use the conversion kit from Vee Twin. This kit uses Wiseco forged aluminum pistons which have a "dish" machined out of the crown, allowing it to use the stock, unmodified 54 cid head. The smaller 54 cid valves give better mid-range punch, at the expense of slightly lower peak power. The Wiseco pistons have a shorter skirt than the stock H-D slugs, and weigh the same, so they balance properly. They also raise compression from 9.0:1 to 9.5:1. Best of all, the cylinders are pre-honed to match the pistons. I checked mine; they were right on spec. This kit makes the conversion a straight "bolt-on" operation, well within the abilities of a careful home mechanic. Geoff does the whole job, kit and labor, for about a Grand, including cleaning up the valves.
I do not have to be whacked upside the head with a "tar arn," I chose option three. I started with a used 54 cid Sporty, which cost $5000. For another thousand I can run with any stock HD this side of a V-Rod. There are always good used 54 cid Sportys out there, as people tend to move up from that bike, usually to a larger, slower bike. Go figure.
Here's a tip to help you select a good used Sporty. Go to a surgical supply store and buy a cheap stethoscope. Throw away that real cold thingy that goes on your chest, and stick a 12" piece of steel auto brake line into the tube. Go all over the engine you're thinking of buying with it, it not only gives you some idea what the motor's Karma has been, but it also intimidates the Hell out of the seller. The Sporty motor isn't hand-fitted, and they "clatter" some. Normal noises include the following.
A few more tips:
1. Get the HD shop manual, and use it!
2. Let nothing you read online, or hear from "experts" overcome your own good sense.
3. Work clean, work slowly, work smart. Check it. Check it again.
4. A hose clamp over a piece of aluminum roof flashing 3/4"x10 3/4" makes a good ring compressor. Use a new strip for each piston.
5. Polish the rocker boxes while you have them off.
6. Don't start up with the old jets, the mixture will be way too lean, the exhaust temp too high. I watched my brand-new exhausts go deep purple in ten minutes. I am now running #180 high, #45 low, and these would be safe to start with.
I wanted the most horsepower for a reasonable number of dollars. Most of the articles center on maximum power regardless of price. I did only the following to the engine.
Total cost about $1000. Labor approximately 20 hours.
Some approximate but typical "Rear Wheel" horsepower figures for stock bikes (crankshaft numbers are fairy tales).
My bike dynoed at (drum roll, please!) 72 rear wheel HP. In fairness, the power figures above are for unmodified, stock bikes which have not (yet) received the low restriction air filter, re-jetted carb, and low restriction pipes all Sportsters need (and most used Sportsters already have). These basic mods should yield 5-7 additional HP. Still, the higher compression and better head flow seem to have a real effect. Geoff tells me that about $1200 worth of cams and a new carb would buy me another 8-10 HP, mostly at peak RPM. I may be crazy, but I ain't stupid--that ain't cost effective.
The bike is, I have to admit, faster than I am. The 72 HP figure isn't in a league with the numbers (claimed) by some of the rice rockets, but they ain't got the Harley torque. Wrap that throttle open and strange time-space-continuum things start to happen. Telephone poles get closer together, for one thing, and the time between two points contracts. My goggles blew off! It's a gas, and I highly recommend it as an antidote to depression, boredom, and the BS of living in a BS world in a BS time. Go forth and be joyful!
Copyright 2002 by Dave Murray. All rights reserved.