Going Full Bore

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Written by Randy Fox   
Saturday, 03 November 2007
Engine Closeup, Yamaha Road Star
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.

 

Introduction

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.



 
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