My 113ci Nemesis, iridescent powdercoated, 2003 Road Star Big Bore--done in 2007

This article is one of a series which describes how to disassemble, work on, and reassemble the Road Star engine. This particular article describes big-bore options and a bit of engine performance/upgrade theory. See the Complete Engine Tear Down, Orientation article in this series for details of other aspects of engine details.

Be sure you refer to the service manual through all phases of this project.

My XV1600 was top of the heap in 2003 when it was new. But as time passed, other bikes were introduced that caught my eye, and threatened the bliss between me and my Road Star. A few bikes are now bigger, several are more up-to-date, but none of them are the satisfying combination of sweet lines, and raw spirit that I love about my Roadie.

Last summer, since no other scooter out there fit me like my big Star, I decided to rekindle the romance via a major makeover. I committed to more size, more usable power, and more customization. Looking back, it was a great decision--very expensive, but worth every penny to me.

More 'size' meant building a bigger engine. More 'usable power' meant combining the right mix of components. More 'customization' meant taking my time to do a few extra details.

Money was budgeted, space was prepared, a few more tools were purchased, and suppliers were reviewed and interviewed.

My technical research found three basic approaches to scratching the big bore itch. The biggest differences between those approaches (and their developers), as far as I could determine, are as follows:

Patrick Racing-- Uses iron cylinder sleeves in its 108ci and 110ci big-bore kits. You send them your stock cylinders. They bore them, insert their sleeves, and then ship back your cylinders. You must tear down (and build up) your engine's heads and cylinders.

Based on my discussions with Jamie and Nigel Patrick (PR Owners), PR emphasizes horsepower and torque. The bread and butter of their components are their JE 10.25:1 pistons, CNC machined head porting, and Serdi valve grinds. These are good quality performance parts, available unbundled or kit form.

Patrick Racing also offers a 122ci option. However, you must disassemble your engine to a certain degree, and ship the bulk of your engine for them to build for you. See the “Choosing How Big to Go” section below.

Orient Express-- Bores and ceramic re-coats your cylinders in its 108ci big bore kit. You must tear down (and build up) your engine's heads and cylinders.

Based on my discussions with Skip Dowling (OE Owner), OE emphasizes reliability and longevity, using components such as the JE 10.25:1 pistons. They also have a very large menu of other, related high performance components and services. This includes expert porting for heads, Serdi valve grinds, oversize valves, cams, etc. These are good quality performance parts, available unbundled or kit form.

In addition, they offer a 21-day exchange program for their kits, so you can get your job done quickly.

Orient Express offers a 122ci option. However, you must disassemble your engine to a certain degree, and ship the bulk of your engine for them to build for you. See the “Choosing How Big to Go” section below.

Note: Due to the ceramic re-coating process, cylinders will be returned stripped. This means, you will need to paint or powdercoat them.

Nemesis Racing-- Note: Nemesis Racing is no longer supplying big bore kits. Supplies iron cylinder sleeves in its 108ci and 113ci big-bore kits. You must have a local machinist bore your cylinders, and insert the sleeves. In addition, you must tear down (and build up) your engine's heads and cylinders.

Based on my discussions with Greg Wicks (NR Owner), NR emphasizes the best components money can buy, for a given application. Nemesis uses only Omega Racing 11:25:1 pistons. All parts are available unbundled.

Note: If the Nemesis kit you choose is their 113ci, you must tear down (and build up) your engine's crankcases, subassemblies, and transmission.

I chose Nemesis for my primary big-bore supplier. But if you make different choices, your parts are likely similar in installation to mine so the procedures I show should still work, basically.

Everyone has their own tastes and goals for a project like this. You'll have to make your own choices. Each choice you make will affect the complexity of your project and the final outcome of your bike. My choices resulted in a rather high project complexity, so you may be able to skip some of my steps if you make different choices. Here's what I liked about the parts I chose:

• The Nemesis 102mm diameter, (113ci) pistons are only 17 grams heavier than stock. The more your new piston weight varies from stock weight, the more vibration the engine will produce. To counteract this, well equipped machine shops will be able to re-balance your crank, if you're willing to split your crankcases to remove it. Also, please see the Supplier Selection section at the end of this article.

I did not have my crank re-balanced. It would have cost an additional $100 or more, and (according to Nemesis) the re-balancing would have been minor because of the tiny weight increase.

• Nemesis Racing valve springs are just slightly stiffer than stock, but offer the longest travel of any aftermarket springs, to help prevent valve float at high RPM. I like that idea. I mean, ideally, you want to use as little of the engine's power as possible to push valves down. Unduly stiff springs consume power and wear valve-seats.
• Nemesis coils and Nemesis sparkplug wires. Here's what Joel (Odo) Parker (Road Star Clinic author, and professional Yamaha mechanic) has to say:

“… Our coils are rated at 1.53 ~ 2.07 ohm resistance, (99 to 03's), so, getting that rating right in there with how our systems work, is essential.
The Dyna coils for our R*'s are 2.2 Ohms, (A little too high). The Nemesis coils are 1.5, ('JUUUSSSTTT' right). More spark for the system.”

• The Mikuni HSR42 flat-side carburetor has worked out so well, I could kick myself for not installing it sooner. The throttle feels so much more predictable. It's a major upgrade experience, with a minor installation difficulty. However, not all Mikuni HSR42 carbs are the same. Some are sold with brackets for using stock throttle cables--others are not. Some are sold for use with a fuel pump--others are sold for use with out. Some suppliers will pre-tune the carb for your bike's setup--others will not. You must decide all these issues, in addition to price. I got mine from Bulldogscustomcycle.com.

Note: Do not try using your stock carb with a big bore engine. As I understand, trying to get it to work well is a nightmare, and it severely limits the engine's power potential.

• 4-Gauge starter cables, or other larger gauge wires, are nearly a necessity for a big bore engine. See the Installing Bulldogs Starter Cables and a Warrior Starter article in this website for more information.
• The Barnett clutch kit consists primarily of a replacement pressure-plate and springs. The rest of the stock clutch setup is purported to handle the greater power of a big bore without difficulty. The stock pressure plate, however, just won't handle the power of a properly built big bore engine. See the How to Install the Barnett Clutch With New Oil Pump Gear in this website for more details.

Some have had success with using the pressure plate set-up from the Road Star Warrior. I chose to go with the Barnett to be sure.

• A Warrior starter is not absolutely necessary, as I understand, but I installed one just the same. It has about 35% extra power over the stock one. I didn't want to tempt the motorcycle gremlins, and get stuck somewhere with a burned-out or feeble starter. See the Installing Bulldogs Starter Cables and a Warrior Starter article in this website for more information. I got a chrome one from www.sxygramps.com.
• There are 4 choices in pushrods: Stock, Adjustable aluminum, Adjustable titanium, Custom made fixed length.

I learned that adjustable pushrods for Road Stars, regardless of where you buy them or who’s name is logo-ed on them, are manufactured by Smith Brothers. Therefore all I had to do was compare prices. I went with Nemesis Racing aluminum pushrods.

Lighter pushrods mean less energy is wasted inside the engine--pushing them up. I could have saved a little more weight by going with titanium, but it would have been three times the cost. I just didn't feel that the microscopic horsepower increase justified the high price jump.

Pushrod adjustability allows you to take most of the top-end chatter out of the engine. See the Assembling the Top End document in this article series for details.

• Several aftermarket lifters are reported to be exactly the same as OEM, but cheaper. I used Sealed Power HT-2011, available from many auto parts stores.

Note: If you replace your cams, you must replace your lifters, according to Nemesis Racing, Crane Cams, and other sources.

This is not a cheap project compared to most others for the Road Star. My project budget detail looked basically like this:

• $950 for the 113ci big-bore kit, including machine work on cylinders and cases.
• $50 for Nemesis Racing adjustable pushrods.
• $125 for Nemesis Racing valve-springs.
• $200 for a Sun (Serdi type) valve-job performed by my machinist, which included installing my Nemesis Racing springs. This is optional, but recommended for an extra horsepower or two.
• $300 for a Mikuni HSR42 carb.
• $275 for a more powerful starter (mine was more, as I got a chromed one). Yamaha Warrior starter (part#: 5PX-81890-01-00).
• $70 to upgrade the starter wires.
• $150 for a Barnett clutch kit.
• $150 for Nemesis Racing intake manifold, which I already had. Optional, but I recommend you install some kind of high-flow manifold.
• $100 in tools I didn't already have, but needed.
• $100-$150 in consumables: gaskets, oil, assembly-lube, YamaBond, etc. My suppliers were: MetricMagic.com, YamahaSportsCenter.com, SportsPlaza.com, and my Yamaha dealer, and O'Reilly Auto Parts.

While you have the engine apart, you may also want to consider:

• Oversized valves-- I skipped this, to produce better low/midrange torque, and to lessen the tendency for carbon build-up in everyday street riding.
• High-lift cams-- I skipped this, to produce better low/midrange torque, and to lessen the tendency for carbon build-up in everyday street riding.
• Ported heads-- I skipped this, to produce better low/midrange torque, and to lessen the tendency for carbon build-up in everyday street riding.
• Upgraded stator and reg/rec-- I went with Yamaha OEM parts. See the Replacing Your Generator Stator and Your Rectifier/Regulator article in this website for more details.
• Aftermarket engine covers-- for the cam & timing areas. These are the "YAMAHA" engraved plates on the engine sides.
• VOES, MAP, or TPS (modified)—optional, but helpful. See the Installing a VOES for the Mikuni HSR carburetor article in the website for more info.
• Stainless steel bolts-- I went with MMS (http://www.mmsacc-stainless.com/html/motorcycle.htm). I sanded and polished them myself--a very dirty, tedious, long job.
• Powdercoated or painted engine-- I went with DK Powder Coating (http://tidyville.roadstarclinic.com/dkcoatings.html). The price will vary, depending on how much of the engine you powdercoat.

Powdercoating is roughly 10 times more durable than paint. Basically, it involves sandblasting, electrostatically charging, spraying a polyurethane polymer dust on, and bake-melting the polymer on, for each part.

Painting is much cheaper than powdercoating, of course, but you must use high-heat paint made for engine (or stove) use. The color selection is more limited, and thorough preparation and proper application is the key to a durable finish.

Gloss finishes for engine parts are generally discouraged, as they are very difficult to keep clean.

Prices listed were at the time of my purchase, and shown in very rounded numbers. Your prices may vary, of course.

Do you want to have the most power for the drag strip or perhaps racing from stoplight to stoplight? Or would you rather have the most power for rolling on the throttle to pass a truck while cruising? You can’t exactly have both.

The basic, engine power equation works like this: To get the highest possible peak-horse-power (dyno) numbers, your component selection will limit your increase in low-and-midrange RPM (normal riding) power.

To get the greatest possible normal riding power, your component selection will limit your increase in peak RPM power and the associated horse power (dyno) numbers.

Properly built, most any big-bore engine will produce noticeable horse power and torque increases in all RPM ranges. So, it's just a matter of deciding what kind of bike rideability you want, and how much money and time you're willing to spend to get it.

I wanted to develop the most cruising roll-on power (torque) possible, even though I would have to settle for a little smaller increase in peak horsepower. This meant that I would not want to use ported heads, oversized valves, or high-lift cams.

After a thorough discussion with my suppliers, I felt that my selections would yield the most rideable, commute-able, and powerful bike for my money and time. Also, I could add the other components later, without another complete tear down, if I wanted.

How big an engine do you want: 108ci?, 110ci?, 113ci?, 122ci? And what are you willing to do to get it?

Going from stock to 108ci or 110ci is fairly straightforward:

• Disassemble the top end of the engine--down to the cylinders.
• Send your cylinders to the supplier or a machinist, depending on which manufacturer you choose.
• Wait for them to machine your cylinders to spec.
• Receive the modified cylinders, new pistons, new rings, gaskets, and other performance parts for you to install.
• Build the engine back up, and adjust your engine to allow for the added power (i.e. carburetion and/or exhaust changes).
• Button everything back up.

Skip Dowling of Orient Express feels that there no inherent performance gains between 108ci and 110ci. It is strictly a matter of bragging rights (actually, Skip’s words were a little more delicately phrased). And all the experts I spoke with agreed that going beyond 113ci created no more horsepower, and stretched the outer limits of the Road Star’s dimensions.

With pistons larger than the 108 - 110ci arena, it is no longer possible to simply take out the pistons and cylinders, increase their size, and put everything back together. This is because the cylinder sleeve diameter exceeds the size of the hole in the crankcases. Then it becomes necessary to remove the engine and transfer case, remove the clutch, generator, cams, crank, transmission and oil pump assemblies, take the crankcases apart (called 'splitting' the cases), send the cases to a machinist, have them bored, clean everything spotless, and then reassemble all the above.

Sadly, Nemesis Racing no longer offers the 113ci kit, which I purchased. This definitely demanded total engine disassembly. It's a lot of extra work, but I elected to do this because I really enjoy tinkering, I wanted to learn every bolt in my bike, and I had the time.

Want to go all the way to 122ci? In the words of Nigel Patrick of Patrick Racing, "If you have to ask how much it costs, we'd rather not do it. The price varies from engine to engine."

Orient Express has a fixed price for their 122ci. However, Skip Dowling, owner, recommends their 122ci engines be used as ‘bar hoppers’ or ‘show bikes’, not daily or long-distance use. All suppliers feel that boring the cylinders beyond 113ci leaves precious little cylinder wall material left.

The Nemesis 113ci and Patrick Racing 110ci big bore sleeves overlap the stud and dowel holes. In the photo to the right, the sleeve is the darker metal, and the cylinder is the lighter metal. You should test-fit the cylinder-top alignment-dowels to be sure they seat completely, are supported vertically and true, but are not displaced from their original position. Every machine shop and supplier makes little mistakes now and then.

If you build your engine without checking this, you just might end up like I did: with a huge oil leak from the head gasket, due to a misaligned cylinder dowel hole.

Supplier Selection

The best motorcycle suppliers offer more than just the products they sell. They also offer support, advice, and encouragement.

We depend on internet and mail-order suppliers for many motorcycle add-ons. And remote suppliers depend on internet and phone orders, to create a large enough marketplace to make their product costs pay off. Let's face it; if we had to depend on local suppliers for all our parts, we'd have drastically fewer choices for modifying our bikes.

It's true that using remote suppliers for after-the-sale-support does take more time than if everything can be done locally. But personally, I enjoyed this. I was in no huge hurry. I was enjoying working on my motorcycle, knowing that some of the most knowledgeable folks in the entire world (the Road Star world) were just a phone call away. This confidence and freedom allowed me to go beyond the homogenized, bolt-on, off-the-shelf mentality.

It's nearly impossible to guess how a supplier will treat you after they have all your money. You have to ask questions beforehand, and observe how they respond. But you should also ask the opinions of others that have used the suppliers you're considering. Forums and user reviews are great resources. Note: The Road Star Clinic website offers both. See the Forum tab and the Star Web Directory (on the Home page) for details.

Just remember to keep a perspective: The experiences of others reflect their opinions and values, and are very useful in that context. But they should not replace your own research and good judgment.

DK Montgomery (Powdercoater extraordinaire and Nemesis North American Distributor) with Author, right, (receiving newly powdercoated engine parts)

All the folks listed below not only helped with their product installs via email and phone calls; they also helped with all sorts of other question-and-answer sessions I had with every one of them:

• Nemesis Racing. Note: Nemesis Racing is no longer shipping products to the USA, so only the few products Nemesis manufactures in the US are still available to us. Greg Wicks was key in helping me build a power plant that still makes me grin every time I ride. He called me several times (from Australia) to help clear up complex issues--even when they had nothing to do with his products.

Most of all, he offered me self-reflecting questions so that I could come up with the exact motorcycle performance I was REALLY looking for. This turned out to be a very different engine than what some others were trying to sell me. He even remained supportive when some of my answers meant that I needed products from his competitors.

• DK Powder Coating (http://tidyville.roadstarclinic.com/dkcoatings.html). DK Montgomery helped me more consistently than anyone else. As North American distributor of Nemesis products, I expected him to help me with details specific to his products, but he talked me through every single aspect of this project. His passion for motorcycles, and work done properly, was obvious from day-one, and never diminished--ever. He even drove two hundred miles to ensure that a package got to me on time and in perfect condition.
• YamahaSportsCenter(.com, Taxarkana). I think these guys know more about our bikes than most, and they are willing to sit on the phone and discuss options and best-approaches. They are only slightly higher priced than Yamaha Sports Plaza of Seattle, and MUCH more knowledgeable.
• BulldogsCustomCycle(.com). David (Bulldog) Tise, and his wife Amy, were extremely helpful, too. David builds Road Star engines professionally, so his advise bolstered my confidence, and got me out of trouble several times.

Thanks to all these folks, and many others--online and off. I would never have attempted this project--nor completed it--without you.

Dedication: To my wife, Celia. She put up with parts everywhere, as well as being pretty much ignored by me for five months. Even when things seemed to be falling apart quicker than they were coming together, she never said anything negative (not one word). Thanks, honey.

To access related articles, refer back to the Complete Engine Tear Down, Orientation article in this series to see which additional articles best address your situation.

Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.

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