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THE TWO STROKE DIRT BIKE ENGINE BUILDING HANDBOOK IS HERE!

11/24/2017

Check out the Two Stroke Dirt Bike Engine Building Handbook

I'm excited to announce that The Two Stroke Dirt Bike Engine Building Handbook is here! We've been working incredibly hard to wrap up the last few details of this project and I'm happy to say we've finally arrived. Book printing is complete, they've arrived at our warehouse, are pre-packaged for shipment, and we've buttoned up the last of the logistical details.

Simply follow this link to grab your copy: The Two Stroke Dirt Bike Engine Building Handbook

The eBook version of the two stroke dirt bike engine building handbook

I want to thank you all for your support and patience as we've worked to finish up the two-stroke book. When I started working on the book shortly after launching the four-stroke book I never imaged it would take as long as it did!

The two-stroke cycle is my favorite type of internal combustion process and I'm thrilled to share my knowledge on how to correctly build two-stroke dirt bike engines. As an engineer I've always been fascinated with ways in which designs can achieve a lot in terms of function while remaining simple in execution. The two-stroke engine exemplifies this by capturing a complex gas exchange process in a handful of moving parts.

While simpler than four-stroke engines, two-stroke engines still must be meticulously assembled in order to ensure they run trouble-free and last a long time. Using the feedback we've gotten on our four-stroke book as a starting point, I set out to write a comprehensive guide that delivers all the information a builder needs to complete a major overhaul from start to finish.

I used three different engines to ensure all the common design variants across manufactures were captured so that the reader will not have a problem tackling any engine build they encounter.

I've also gone far beyond just capturing the rebuild process and have included chapters on important topics that must be understood in order to correctly diagnose problems, inspect parts, and reassemble the engine. Within the book you'll find info on tests used to diagnose problems, a discussion on premature wear, and a thorough how-to on using all the precision measurement tools necessary for correctly inspecting components.

The Value Pack of the Two Stroke Dirt Bike Engine Building Handbook

While service manuals tell you when to do things, I've detailed the how and why behind the entire process of what you are doing. My goal with this book is to increase your engine building knowledge, make you a better engine builder, and explain why it's important to execute each step in a precise and predictable way.

As someone who loves tinkering and making engines perform better than stock, I included sections on performance/race engine building techniques, which cover checking/setting port timing, checking squish clearance, and checking compression ratio.

I hope you enjoy my new two-stroke book and that it makes your life easier. For a comprehensive overview of everything the book has to offer check it out here: The Two Stroke Engine Building Handbook.

Thanks again for all your support as we've grown DIY Moto Fix from an idea to a thriving community of riders who are passionate about making their machines perform better through their own hard work.

-Paul

The Two Stroke Dirt Bike Engine Building Handbook

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How The Two-Stroke Exhaust System Works

11/12/2017

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In my last post, I shared details about how the two-stroke cylinder works, in today's post I want to provide an overview of how a performance two-stroke engine's exhaust system works.

Adding a performance exhaust system can be a great way to increase power and/or alter the power delivery of an engine. I would also argue that optimizing a two-stroke engine’s exhaust system is equally as important as ensuring the cylinder’s ports are correctly designed for the given application. Not all exhaust systems are designed to do the same things, and much like cylinder port design, exhaust designs are intended to alter power in specific ways. Having a basic understanding of how an exhaust system works can go a long way when it comes to selecting the right exhaust pipe for your engine.

Two-stroke exhaust design is complicated and there are many different variables that must be considered when designing a pipe. I don’t intend to go into all of them, but I will share a few of the most critical.

Each time the exhaust port opens to release spent combustion gases, pressure pulses are created. Modern pipe designs harness this pulse energy and use it to help scavenge and fill the cylinder. The process starts when a positive pressure pulse is created once the exhaust port opens and combustion gases leave the cylinder. The positive pulse travels down the pipe until it reaches the diffuser, at which point part of the pulse is inverted and reflected back towards the cylinder as a negative wave. This negative wave is very beneficial in pulling spent exhaust gases out of the cylinder and fresh mixture up through the transfer ports. The remaining positive pulse continues on its journey towards the end of the pipe where it encounters the reflector. The reflector acts as the name implies and forces the positive pulse back towards the exhaust port. Once reflected back, the pulse remains positive and, if the pipe is designed correctly, will reach the exhaust port just as the piston is about to close off the port on the compression stroke at the desired RPM for maximum power. Any fresh mixture which has escaped out the cylinder will be forced back in by the positive pressure pulse.

The tuned length of the pipe is dictated by the exhaust port timing, RPM of max power, and the speed of sound. Pulse length and amplitude are governed by the angles of the diffuser and reflector. Generally, steeper cone angles create pulses with more amplitude but shorter duration. Shallower angles generate pulses with less amplitude but longer duration. Given these variables, it is easy to see how a pipe could be tailored for specific applications. An engine converted for road racing may utilize a pipe designed for peak power which incorporates steep diffuser and reflector cone angles so that pulse amplitude is not sacrificed. This peak power would likely come at the expense of a narrowed range of power. An engine tailored for woods riding may feature a pipe with shallower cone angles, resulting in less pulse amplitude, but a broader spread of power.

The last parameter I want to touch on is how the tailpipe, which is sometimes referred to as the stinger, influences the pipe. The tailpipe creates a flow restriction in the pipe which allows the pipe to have a certain amount of back pressure. Enlarge the tailpipe and the back pressure decreases, make it smaller and the back pressure increases. As back pressure increases or decreases, so does temperature and ultimately the speed of sound. As the speed of sound changes, so does the resonance RPM of the pipe. If the tailpipe is sized too small, cylinder scavenging will be inhibited. When this happens, the cylinder, fresh mixture, and piston will all be overheated.

While engineers and tuners can estimate starting pipe dimensions and tuned lengths, a great deal of trial and error testing is usually still necessary to fine tune the exhaust pipe and optimize the design. Unless you intend on building your own exhausts, this work will have already been done for you.
When selecting an exhaust system, you need to focus on how the exhaust alters the power curve. Exhaust systems are tailored to deliver more bottom end performance, top-end performance, or performance throughout the power curve. Selecting which system is right for you will depend on how you want your engine to perform. If you’ve chosen to modify your cylinder ports, installing an exhaust system that compliments the porting can be very beneficial.

You might be wondering about slip-on mufflers. If you’ve followed along with my explanation of how exhaust pipes work, you’ll notice I made no mention of the muffler. While the muffler can have a small effect on performance, it is not the primary factor. Upgrading a muffler is a good way to reduce weight, but there won’t be a slip-on out there which significantly increases power, in the same way, a properly designed expansion chamber can.

I hope you enjoyed this write-up on key features affecting the performance of two-stroke cylinders. As for Two Stroke Handbook news, we received our first printed proof of the book this last week! Needless to say, we are inching closer and closer to an official release date. To stay updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to sign up, see the new cover, the Table of Contents, and some sneak peek pages right from the book.

Thanks for reading and have a great rest of your week!

-Paul

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Sneak Peek of The Two Stroke Dirt Bike Engine Building Handbook! The Pre-sale Will Begin On...

11/4/2017

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DIY Moto Fix The Two Stroke Dirt Bike Engine Building Handbook

The DIY Moto Fix Team is pleased to announce that we received the first proof of The Two Stroke Dirt Bike Engine Building Handbook this week, so we had to get some beauty shots of the print book out in Paul's workshop to show it off to you!

First off, this soft cover book is 8.5" x 11" and weighs over 2lbs. We are happy to bring you nearly 300 pages of engine building knowledge and over 300 highly detailed color photos. Take a look at the photos below to learn more about what's packed into the handbook.

The Two Stroke Dirt Bike Engine Building Handbook features an entire section dedicated to inspecting crankshafts. Within it, a comprehensive overview on how to measure runout, pinpoint surface wear, and true crankshafts is discussed. In the photo below the book is discussing the three types of crankshaft misalignment conditions that can be present on new and used crankshafts.

The handbook covers a lot more than just engine building technique. We strove to put together a comprehensive reference that helps someone perform a major overhaul on their engine from start to finish. Here's a complete list of all the chapters that you can expect to find in the book:

How To Use This Book
When To Rebuild
Diagnosing Trouble
Leading Causes of Engine Wear and Failure
What To Replace
Engine Building Tools
Service Manuals
Precision Measuring
Your Workshop
Race and Performance Engine Build Considerations
An Overview of A Build
Engine Teardown
Inspection
Final Assembly
Setting Ignition Timing Dynamically
Engine Break-in
Maintenance Logging
Closing Thoughts

In the photo shown below, we're one page into Chapter 12 and only about halfway through the book!

Did we mention this book is thick? We went beyond providing basic information and included more detailed explanations throughout the book. Littered within the chapters are detailed sub-sections and pop-outs that we've deemed Race Engine Engine Building Techniques, Technical Takeaways, and Hot-Tips.

Race Engine Building Techniques cover topics that would fall outside a normal engine build, but are standard practice for builders who are preparing performance engines. Race Engine Building Techniques are often lengthy in discussion and can span several pages at a time. Examples of these techniques covered in the book include: Setting and Checking Port Timing, Checking Compression Ratio, and Checking Squish Clearance.

Technical Takeaways are sub-sections that detail the how and why behind specific engine building techniques as well as highlight the appropriate procedure for the given task. Technical Takeaways are often used to introduce repeated tasks once so that they can quickly be referenced later. Examples of Technical Takeaways include: Installing/removing bearings, tightening sequences, and retaining ring installation.

Hot-Tips are quick blurbs that fall outside the normal discussion, but can add incredible value depending on the user's specific situation. Hot-Tips also serve as a way to communicate friendly reminders of things to double check or do prior to proceeding on with the build.

Thanks for taking a look at what The Two Stroke Dirt Bike Engine Building Handbook has to offer!

When does the pre-sale officially begin?

We are excited to announce that our pre-sale will begin on Friday, November 24th (Black Friday) and end on Monday, November 27th (Cyber Monday).

So you will have a four day window to reserve your copy - whether it be print book, eBook, or both - at 20% off the list price.

Feel free to pass this info on to a loved one so you get a holiday present you actually want! Sign up below and we'll email you the moment the 2T book pre-sale is up and running. A huge thanks to those of you who have already signed up!

To stay updated on the 2T Book Sign up below.

We will email you the moment the handbook is available for pre-sale on Friday, November 24th!

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THE TWO STROKE DIRT BIKE ENGINE BUILDING HANDBOOK IS HERE!

How The Two-Stroke Exhaust System Works

Sneak Peek of The Two Stroke Dirt Bike Engine Building Handbook! The Pre-sale Will Begin On...

When does the pre-sale officially begin?

To stay updated on the 2T Book Sign up below.

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