Sportster 883 to 1200 Conversion

Sportster V-Twin

Update!: Sportsters since 2004 include a number of changes, notably a rubber-mounted engine and slightly redesigned top-end. While these instructions should work in principle, please examine the service manual for the bike closely to make sure that you are following the right procedures. I haven't seen one of these beasts taken apart yet, so I can't say whether any of the instructions below needs an update. If you know something that you think I should include here, please e-mail me, and I will revise the document.

I'd love to put pictures up along with this, but I simply don't have access to any good ones I can legally post here. If anyone reading this article is willing to donate decent diagrams (and won't get offended if I either don't think they're acceptable and don't use them or do think they're acceptable but modify them), I'll include them in the article and give you credit. Drop a note to the address below.



Table of Contents

Conversions I Haven't Tested
Opinions and Prejudices Up Front
Preparation—stuff you'll need
Taking it apart—bits & pieces
Details of the change—change is good
Breaking it in—easy does it
Conclusion—Appreciation to the Masters


Converting the engine of a Harley-Davidson Sportster from 883cc to 1200cc is one of the best hop-up bargains on the market. The cost of the parts is relatively low. The whole process is simple and can be completed without a lift and with the engine in frame. The description that follows isn't intended to take the place of detailed technical instructions, but it can supplement those by describing some shortcuts and point out some pitfalls. Some other experiences are documented on the World Wide Web and in magazines and would be helpful to read through before you begin:

  • Hot Rod Bikes, "How To Build a Hot Rod Bike" (Peterson) You can probably get a reprint of this article through the magazine.

  • "Adding Muscle: Sportster 883 to 1200 and More!", Hot Bike, July 2000, pp. 108-110.

Conversions I Haven't Tested

I have heard that Wiseco now offers an 883cc to 1400cc conversion kit, too, but I have no experience with that yet. The steps involved in that conversion should be mostly the same, but always follow the manufacturer's instructions. Harley-Davidson now offers a reverse-dome piston for this conversion as well. While I try to remain technically unbiased, I do generally favor Harley-provided parts over third parties—they always seem to fit just right and work reliably. That being said, Wiseco has a superior track record and manufactures products you can trust (my opinion). No matter which of these alternatives you might consider, the instructions that follow work pretty much the same. I think I might modify the break-in guidelines for the 1400cc conversion . . . .

Opinions and Prejudices Up Front

Keep It Simple

No matter what, don't read anything (including this) and be concerned about every little detail. For example, how much gaskets will crush when everything is torqued down is generally irrelevant if you are using the right components. It is my opinion that Hylomar, gasket sealer, or any other kind of goop is unnecessary for this job. The service manual doesn't indicate you need it, and every place you're going to put a gasket will have a pin or journal to hold it in place. If you are going to install cams at the same time, a couple of (really tiny) dabs of Hylomar can help free up some fingers for getting the cam cover back on. Nothing in the process requires you to use Loctite, so resist the temptation to really glue things down. A little anti-seize, on the other hand, is probably appropriate in certain places as described later.


If you plan on installing new cams at some point, you should probably break the "keep-it-simple" rule and do that at the same time you do the conversion. You'll have the top-end off anyway, and you have to take the rockers off at least as part of installing cams. Any cams worth installing will probably require you to use beefier valve springs that you can get installed while the heads are off.


Some people swear by all sorts of carb modifications or after-market carburetors. The stock CV carb properly jetted and adjusted is darn near perfect for street use. I have no experience with Mikuni, but people I know like them. (I think the Screamin' Eagle flatside is actually a Mikuni.) I do have experience with the S&S Super E, and it is a great all round performance product—simple to jet and adjust and practically indestructible. Because it is not a CV, it has some limitations that you'll probably never notice if you're just riding around town. Best bet during the conversion is to keep the carb you've got and make sure it's jetted right.

Preparation—stuff you'll need

Get Organized

It's usually best to have everything you need before you start. The most important item is the service manual matching the year of your Sportster. Don't do anything or buy anything else until you have this and have read through the sections about engine disassembly and assembly. The second most important item is cash (or a credit card). You'll need some of this to buy the necessary parts. Finally, you need appropriate tools—a set of standard sockets, Allen heads, and a torque wrench. Harley has started using Torx fasteners on some of its newer bikes, so you may as well have a set of Torx heads as well, just in case. You will need a 12 point socket to remove and tighten the head bolts. (Do not try to get around this—strip the head of the bolt on one of these babies and you'll be crying.) You'll need a manifold tool—it's a kind of s-shaped Allen-wrench-thing that really simplifies getting at the Allen screws holding the manifold in place. (It will save you more aggravation than the few bucks it costs.) Get a top-end gasket kit for your year Sportster. Get about 4-5 feet of clear 3/8" (inside) vinyl tubing. (Lowe's or almost any Home Depot kind of place has it.) You can cover the cylinder studs with pieces of it to protect your new pistons when the time comes. You will need some clean shop rags, enough engine oil to perform an oil change, a tube of assembly lube, and a tube of anti-seize.


The upgrade parts will require a couple of decisions—bore or replace the cylinders; use Harley or after-market pistons. Boring the 883 cylinders out to 1200 is a little cheaper than buying a new set of 1200 cylinders, but conventional wisdom is that bored cylinders will run a little hotter because of thinner cylinder walls. (I'm not sure about how much this matters because the stock 883/1200 cylinders are virtually identical except for bore in the liner and the little "883" or "1200" cast into the base below the bottom fins on some parts.) If you get them bored, they should come back with the dowel pins installed. You'll probably have to install dowel pins in new cylinders. Also, boring the cylinders is a precision job, so you want to make sure that whoever does it has high standards, the right equipment, and skill. The dealer can support either decision for you. If you use Harley pistons, you'll need to get some head work done. Wiseco reverse-dome pistons are more expensive than stock Harley pistons, but you won't need any head work. If you have more than 20,000 miles on the heads, it may be worth having them looked at and freshened if necessary. A more expensive alternative is to slap on a set of Buell Thunderstorm or Screamin' Eagle heads—no modification required. If the head bolts on the engine are rusted or discolored, go ahead and replace those, too. (New ones will look nice on your freshly upgraded engine.)


Finally, you'll need a comfortable spot to work. If you decide to push the bike into a walk-in basement, the gas tank comes off first! Remember to maintain a healthy respect for the flammability of gasoline. Every year the local paper reports at least one fire that involves a motorcycle, a gas tank, and a pilot light. The garage is just as dangerous if you are a smoker or are using a space heater. If you have to dispose of gasoline, do it in an approved container. You can change the oil at the start or the end of the process. Once you have all your tools, parts, and workspace prepared, you are ready to begin.

Taking it apart—bits & pieces

Getting Rid of Fuel

The last time you run the engine before the upgrade, close the fuel petcock but don't shut off the engine. Let it idle until it stalls. That way, pretty much all the gas will be out of the carburetor. The service manual has good instructions for stripping the engine. Put the battery on a charger to make sure it has lots of juice when you hook it back up—it'll have to work harder to move the pistons with new rings. (There are safety instructions that came with the charger, and you've read and understand those.) Do not try to do the conversion with the battery in the bike. Have a plastic cup handy to hold under the fuel line when you disconnect it from the carb. Any gas that may still be left in the line will run out. You can then just take the cup and dump the gas back into the tank. Carefully remove the tank and place it to one side.

Removing the Heads

Have some paper spread out under the engine and keep a few shop towels handy when you remove the rocker box. Take off the lid and the spacer first so you can see the rocker arms. Assuming you are working without a lift, you can rotate the engine so that all the valves are closed by simply rolling the bike a few inches across the floor in 4th or 5th gear with the spark plugs removed. It will still resist a little, but you'll be able to see all the push rods settling to their lowest point. Because of the 45-degree angle of the cylinders, a little oil tends to pool at the exhaust side of each rocker. When you start removing the lower portion of the rocker box, that oil will dribble out, so have a cloth handy. Once all the bolts are out of the lower rocker half, but before you take them off, slide them around a little so that you can remove the push rods first. Label each push rod according to location (FE, FI, RI, RE) and orientation (which end is the top). They have to go back in exactly the same way. If you take the push rods out first, the rocker-arm assemblies slip out easily.

New gaskets seal better but seem stickier, too, so they almost always seem to leave hunks behind stuck to the bottom of the rocker assembly or to the head. A new razor blade is usually enough to carefully peel off any remnants. Try not to score the surface of the aluminum. For uncooperative bits, apply a little gasket remover with a q-tip to soften it up. (Don't spray gasket remover right on the head—it's messy and may get on other things the finish of which you'd prefer to preserve.)

The service manual would have you disconnect the throttle cables and remove the carb, but a shortcut is to leave the carb attached to the throttle cables and let it dangle out of the way. It won't be that way for long. Throw away all the old gaskets and o-rings as you go along so that the only ones that end up back in the engine are the new ones. Follow the service manual instructions for removing engine mount bolts and loosening the head bolts so you don't distort the cylinders.

Cylinder Removal

When you arrive at the point where the heads are off and you are ready to remove the cylinders, make sure that you have your clean shop rags handy. If you have compressed air in your garage, blow any dirt or grit away before you go further. Otherwise, improvise and get the area as clean as practical. Next is an important step that isn't always described. The cylinder will slide off the piston easily. When you have pulled it several inches away from the engine case but before it is completely off, stuff a couple of shop rags into the cylinder bore in the engine case and around the connecting rod. This is to make sure that no junk or dirt or carbon fragments or anything else can fall down into the engine case. That would be bad. It should also keep the connecting rod from banging against the cylinder bore. Think about debris inside the engine case until it makes you nervous, then you are ready to remove the cylinder. Pull it off the engine straight and without stressing the cylinder studs. Bend those and you'll have a whole new project that this article won't help with. (This would be another of the bad things.) Slip the vinyl tubing over the studs to protect the threads and the new pistons if you're planning to use a ring compressor to install them.

Be Neat/Be Careful

Once both the cylinders are off and the top of the engine case is plugged with shop rags, gently remove the base gasket or any of the fragments that may have been left behind if it tore off. With another clean shop rag, make sure the surfaces are nice and clean. If any material is stuck to the case, carefully peel it off using a new razor blade, trying not score or scratch the surface. Remove the circlip from one side of the old piston with an awl or small screwdriver. Wear a pair of safety glasses in case the clip pops out at you. (It won't hurt or anything if it hits you unless it gets you in the eye—something to add to the list of bad things.) Carefully push the wrist pin out, and the old piston will lift off. The wrist pin will yield to finger pressure. No need to bang it with anything. Take a break. It seems to go back together faster than it comes apart. If you have a set of cylinders ready to go, you don't have to wait. If you're boring your old ones, you'll have to wait until they come back to go to the next step.

Details of the change—change is good

Whom to Trust

Lots of opinions circulate about the right and wrong and best and worst ways to do things. When in doubt, trust the service manual first. If it isn't clear enough, ask a trained Harley mechanic. For example, some of the instructions posted on the Internet would have you slopping gasket sealer around and experimenting with specialty after-market gasket products. I don't know whether that stuff is any good, but one thing is relatively certain—sticking with stock H-D products and keeping glues and goops away from them will probably be easier and make for a more reliable rebuild.

New Pistons

While not essential, it is a good idea to try to make sure that your new piston/wrist pin combination weighs as close to the same as the old as possible. This will minimize vibration and extra stress on the engine. If you need to reduce weight, you can get a set of lightened wrist pins. This may be necessary in newer Evo engines. Advice from an expert on this point can't hurt.

The various installation steps you need to understand are included in the service manual and with the piston kit. Remember, if you don't understand a step, or something is not clear, ask someone—better to feel dumb with a new part in your hand than to feel really dumb with a broken one. (You can always send a message to me at the address at the bottom of this page if you're not in a real rush for an answer.) Two things to pay particular attention to are piston and ring fit. If cylinders are bored a few thousandths over, they will need matching pistons. The service manual also includes instructions for installing the piston rings. While almost any set of rings will go on right out of the box, they must be fitted carefully per the service manual instructions. One reader told me that he had a good shop hone the cylinders, match the pistons, fit the rings, and install the pistons in the cylinders all for a pretty reasonable price. That can save you some time and anxiety.

No Ring Compressor? No Problem.

Another technique that isn't always documented is how to install pistons without using a ring compressor. There is enough room between the engine case and the top of the frame to do this. It seems that about half the world uses this method, and the other half would never even consider it. Decide which half you're in, then proceed according to what you choose to believe. To install pistons without a ring compressor, just follow these steps. (I guess this reveals which half of the world I decided to join for this exercise.) Before you start, install the circlip into one side of the piston. It'll simplify wrist pin installation later. Make sure the gap in the circlip is opposite the gap on edge of the wrist pin hole.


Lightly oil the inside of the cylinder. Don't overdo it. You just need enough so the pistons can slide easily. Turn the cylinder upside down on the counter or other clean flat surface. Spreading out some newspaper is recommended if you are married and have notions about remaining so. Pistons have a front side (thrust face) and a back side. On a Harley, the thrust face of the piston points toward the exhaust. The piston will have an "X" or an arrow marking the thrust face.** (See note below.) Remember, too, that cylinders only install one way, so make sure you know where right, left, front, and back are before you start trying to shove things into them.

Orient the Ring Gaps

Assuming that you have all the rings oriented properly on the piston—you followed the service manual, right?—gently insert the piston into the cylinder at a slight angle so the side of the first compression ring away from the gap slips into the cylinder. Slide your fingers around the ring until you've closed the gap as much as you can pushing gently at the same time. The ring should slip right in. Follow this process with each ring. By the time you get to the oil rings, the piston won't tilt much, but it will enough to complete the operation. A little gentle tapping with the palm of your hand can help. Be careful not to slide the piston in too far. You need enough room to insert the wrist pin. That means the rings will be barely into the cylinder. Lightly coat the wrist pin with assembly lube and push it far enough into the side of the piston that it won't fall out, but still leave room to fit the piston over the connecting rod. When you flip it over and look down inside, you should see the marks on the top of the piston pointing in the correct direction. If not, pull the piston out gently, re-orient it, and follow the instructions again.

Keeping Stuff out of the Engine Case

The service manual instructions for assembly are excellent and don't need to be repeated here. What the manual doesn't say much about is keeping crap out of the engine case. Before you install your new cylinder/piston combination, make sure the area where you will install the base gasket is nice and clean. Get any dirt and debris away first. Gently remove the rubber tubes you left over the cylinder studs. (These will have mattered more if you installed the piston on the connecting rod first and pushed the pistons in with a ring compressor.) Gently remove the shop rags and shake them out away from the engine. Gently slide the base gasket down over the cylinder studs. Gently put the shop rags back in the opening. By the way, did I mention that this should be done gently? The reason for leaving the shop rags in there until the last minute is simple—if you drop a circlip when you are installing it over the wrist pin, you don't want it falling into the engine case.


Assuming that you have the pistons protruding from the bottom of each cylinder, their installation is quick. A set of spare hands can help you steady the cylinder, and can make the work a bit lighter. Carefully orient the cylinder and piston over the connecting rod and cylinder studs. Make sure you've put a little oil or assembly lube along the wrist pin journal inside the piston. When the piston and connecting rod are lined up, the wrist pin will slide right in. It will not need any banging or tapping, just firm finger pressure. Once the wrist pin is in place, install the remaining circlip. Just like before, make sure the gap in the circlip is opposite the gap on edge of the wrist pin hole. Check both sides before you go any further. If you have not oriented the gap in the circlip right, it could work its way out making a real mess of the inside of your engine. If everything is in place, gently slide the cylinder down over the piston and cylinder studs. Stop while you still have room and take out the shop rags. Make sure the base gasket is lined up and flat, then slide the cylinder the rest of the way, and seat it. Follow the same steps for the other cylinder. It's usually a good idea to take a couple of the head bolts and screw them down (finger tight) onto a couple of the exposed cylinder studs to keep the cylinder secure until you're ready to put the heads back on.


Head gaskets are next. The only trick to the head gaskets is that each one has a few pieces—the gasket itself and little dowel pin o-rings. The o-rings have to go on first so that you can orient the gasket. Place all the gaskets and o-rings carefully so that nothing is pinched or protruding or misaligned. Gently sit the head on top of the cylinder. The dowel pins will line everything up. I wipe a little bit of anti-seize on the head bolts using a q-tip—just a film, not a glob. Put in the head bolts, and tighten them with your fingers. Follow the same procedure for the other head. You can torque the bolts on each head individually, or you can torque them when both heads are on. Follow the service manual instructions for torquing the head bolts exactly. No shortcuts here. The service manual is very specific on how you should do it. Do it that way and only that way. After this, assembly is simply reversing the disassembly steps. The service manual has a good walk through. Applying the anti-seize is an optional step.

Finally, you'll probably want to re-jet the carb to make sure that you're getting enough gas into the larger cylinder volume. The bike should run with the previous set-up, but you'll probably have to richen the mixture up to keep the engine happy. Starting with a 45 pilot and 175 main jet is a reasonable and cheap upgrade.

Breaking it in—easy does it

Stay Calm

Once everything is back together, you'll be dying to get out on the bike and see how much additional power you have. Be patient, the break-in will take about 500 miles. When you start your new 1200 for the first time, make sure that your battery is well charged. The new pistons will be tight and use all the cranking power your battery has. Don't be surprised if the engine doesn't seem to want to turn right over like it did before. A little hesitation is normal. Once it is started, let it idle for a few minutes so that the oil can get around to all the places it usually goes. Any initial odd ticking sounds should fade into normal engine noise in about a minute. You'll notice first that the exhaust note is a little lower. Some bikes may need some tinkering with the idle speed and mixture because the settings used for the 883 will be a little lean for the larger cylinders. Re-jetting the carburetor may be an option if you find later that the bike feels a little fuel starved. Having read the break-in recommendations below, you'll also notice as you pull out into the street that the bike seems to have a much deeper well of torque—an excellent thing.

Break-in Guidance

Keep the engine below about 45 MPH for the first 50 miles. Even if it doesn't make any mechanical sense, it will get you used to the coming days of low-speed travel during break-in. The recommended break-in is 500 miles. Keep it below 3,500 RPM during that period. The manual that came with your bike includes break-in instructions. What was good when the bike was new is good when the top-end is new. The following are typical recommendations:

  • Keep engine speed below 2,500 RPM in any gear for the first 50 miles.

  • Up to 500 miles, keep engine speed below 3,500 RPM in any gear. Vary engine speed, avoiding long distances at one speed (10 or 15 minutes could be considered a long distance at one speed).

  • Avoid fast starts with a wide open throttle. (You may be tempted.)

  • Avoid lugging the engine at low RPM in high gears. (It will be easier to pull from a low speed in a high gear with the 1200.)

  • Do not exceed 50 MPH for the first 50 miles. (You will be tempted.)

  • Do not exceed 55 MPH for the first 500 miles. (You will be sorely tempted.)

If everything was buttoned up right, you should not see any oil seeping from anywhere where you did your work. In one set of Internet instructions, the writer noted an oil leak that was most likely a consequence of using a combination of after market gaskets and some kind of goop to stick them to the engine. (Don't do that.) Change the oil after the first 500 miles. Some people say you can wait to 1,000, but oil is cheap TLC for your bike, so go ahead and change it. Do not use synthetic oil of any kind in the engine during the break in period. If you do, the rings will not seat properly. Synthetic versus conventional oil is another of those religious disputes that seems to divide the world in half. (Someone else can write that article.) In the case of a new 1200 conversion, the synthetic half of the world does not exist until after about 3,000 miles.

Conclusion: Appreciation to the Masters

This exercise will generally teach several lessons about how Harley-Davidson has engineered its products. Other manufacturers build fine motorcycles, but the Harley V-twin is smart, elegant, and simple, all at the same time. Those qualities make the work easier from the start. The work on which these instructions is based would not have been as quick and painless as it was without advice and guidance before, during, and after the project from Earl Ditamore (master mechanic at Whitt's Harley-Davidson, Manassas, VA) and Rob Schopf (master engine builder at Hal's Harley-Davidson, New Berlin, WI)—their brains, my hands.

If you think this little article was helpful, have suggestions, or just want to tell me about your experience with the upgrade, feel free to send me a message. I have heard from Sportster riders all over the world, and every story is interesting. As a defense against spammers who make life a misery for all of us, the e-mail address is hidden behind a reCATPCHA challenge. Just enter the words in the picture, and the address will be displayed.

Good luck with your upgrade, and ride safe!

** Note:

From Dave Fussner, Wiseco Piston Co., Inc: "In years past the arrow on a Wiseco piston always pointed to the exhaust side. And in fact, up until a few years ago, this was also true in Wiseco pistons for Harley-Davidsons. However, a few years ago Wiseco changed to offset wrist pins on our Harley pistons as a quality improvement. So for proper installation, these pistons are to be installed in both cylinders with the arrow/FWD mark facing the front of the bike." Always verify the piston orientation with the instructions provided with product you'll be using.

Copyright © 2001-2006 by Philip J. Holt

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