What Constitutes a Street Engine? Part II

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August 7, 2010 | By: J&P Cycles

Editor’s note: Today we present the second of two blog entries comparing race bikes and street machines. Yesterday we heard Scott Holton’s description of the attributes of a good race bike. Today, we explore the definition of a street bike, expertly presented by our own Anthony Todd.

By Anthony Todd

Scott did a great job explaining how wild you can go before you get to the point of no return when it comes to engine building. His explanation raised this question in my mind: If we modify our engines from their stock form how can we still label it a “street engine?” So I re-read his post and thought about how modifying my engine can sacrifice my comfort, drivability and reliability as a daily driven motorcycle on the street.

First, Scott mentioned compression and how higher-compression engines can create more heat. Heat from the engine on a rider or passenger can make or break the difference in riding 5 miles or 500 miles. Anyone who has driven a late-model Harley in traffic knows this first hand. So when planning out an engine you need to keep in mind compression and how it can affect temperatures in the various operating ranges.

Scott also mentioned octane ratings in his post. Today’s performance motorcycles and race engines require 93 octane or higher to perform at peak performance. What does that mean to a street rider? It may require you to think about where and how often you refuel. If your engine is limited to no less than 93 octane, you might not be able to plan trips around small towns or mountainous areas due to the paucity of higher-octane fuels.

To me, the most important factors are reliability and drivability. I should be able to walk out to my garage, turn the key and ride any time I want, whenever I want. Once you start modifying your engine, things can get out of hand. If you don’t pay close attention to all the components you install, you may find yourself upgrading components like your charging system, starting system and your fuel system. These components can become very expensive and if not set up properly, they can mean the difference between riding with your friends when the weather breaks, or performing tedious yard work you’ve been putting off for weeks.

So to me, the definition of a street engine is any engine that will be reliable, comfortable and not keep me from enjoying the open road at any point. My intention is not to keep you from modifying your engine. I just want to explain the consequences of what can happen if you don’t do the homework prior to an engine build, or if you don’t consult an educated engine builder. Hundreds of customers contact our technical staff each week to purchase components to improve their motorcycle’s performance. And the first question we ask each customer is this: “Are you racing the bike, or riding it on the street?

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All Strokers Are Race Engines Then

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