With warmer weather and the riding season around the corner for many of us, I wanted to cover a topic that can either make or break an event. Whether you’re competing in a racing series or traveling to the track or trail, let's talk about event preparedness. More specifically, what spare parts should you keep on hand? Plus, what methods do you use to keep your spares organized?
Today I want to share some updates about what my friend Matt over at How-To Motorcycle Repair is up to. For those of you that don't know, Matt runs HTMR which, similar to DIY Moto Fix, is tailored to helping riders maintain and service their machines. Matt is heavily invested into the video side of things and has over 32,000 YouTube subscribers, has been producing videos for over five years, and is always improving his setups.
The content Matt is producing is intended to provide a one-stop resource for folks who need help fixing their machines. Matt's videos are diverse in make and model and the topics he covers range from carburetor rebuilding to full engine rebuilds.
I have to give Matt a lot of credit because he is a one man band. Matt is filming, working on the bike, and editing his videos all on his own which is an impressive undertaken. To improve video quality Matt recently updated his camera and audio equipment which has led to an enhanced viewing experience.
Similar to us at DIY Moto Fix, much of the content Matt creates and offers is free but he does charge for his in-depth detailed videos. In the spirit of two-strokes and my new book, we wanted to share a couple of his two-stroke videos which may help some of you out.
First up, is his recently launched KTM 250/300 top and bottom end rebuild video which covers numerous model year KTMs, Husqvarnas, and Husabergs. In conjunction to the video on the HTMR website, you'll find supplemental information on the tools needed to tackle the job, a summary of replacement parts required, and resources for tracking down a service manual.
Matt's second video details a Kawasaki KX250 top and bottom end rebuild which is applicable to 1994-2007 KX125 and KX250 engines. In these videos Matt tackles all detailed tasks associated with the engine build and covers the KIPS power valve system in detail. To ensure the viewer gets a comprehensive understanding of the KIPS setup Matt uses multiple camera angles and two assembly sequences to cover the process.
If you're a visual learner, Matt's diverse array of videos is incredibly helpful. For anyone interested Matt has extended a special offer code which can be used to get 20% off the price on any of his videos. Simply enter, diymotofix20off at checkout to take advantage of his offer.
For anyone that wants to learn more about Matt and HTMR check out his website at: www.howtomotorcyclerepair.com/
Thanks for reading and have a great week!
“Splitting the cases” is often referred to as a daunting or undesirable task, but if you are well prepared and properly equipped then it can be a straightforward job. To alleviate any concerns you may have with the task, I want to discuss best practices and share some tips that you may find useful when dealing with crank bearings that utilize an interference fit with the crankshaft. We’ll get started by discussing preparatory items and work through to completing the job.
I hope you’re all surviving and hopefully enjoying the winter months. This morning half a dozen steps out the door I was already on my ass, solidifying my first fall of the year. I guess I have to make up for the number of falls I would have otherwise suffered on my ice bike.
Today, I want to provide an update on the progress I’ve made on setting up my workshop. Overall, 2017 was a good year of growth when it came to acquiring power tools and equipment. The floor plan I originally shared may not ever come to fruition, but I have started to distinctly define certain areas of the shop.
For reference, here’s the original floor plan I came up with:
I hope the holidays have been good to you all! The new year is one of my favorite times of the year because it serves as a time to stop and reflect on the past, assess the present, and prepare for the future. Today I want share with you how I did on last year's goals and discuss my plans for 2018.
Let's take a look at how I did on the goals I set for myself in 2017:
1. Publish The Two Stroke Dirt Bike Engine Building Handbook. - Done! The two-stroke handbook started shipping on December 5th. In case you missed it you can check it out here. Thank you to everyone who has bought a copy of the book and has supported our efforts! If you've had a chance to read the book please shoot me an email and tell me what you think of it.
2. Publish quality content to the DIY Moto Fix blog bimonthly for all you awesome readers. - I averaged one post per month so I did not hit my bimonthly goal.
3. Go solo in a 3-hour endurance ice race and complete it successfully. - Done! I raced the "Frosty Cheeks" 3-hour endurance race last January. If I recall correctly I finished 4th or 5th out of 6 entrants, suffered through many cramps during the race, and had a completely flat ass at the end of it. That said, I would do it all over again!
4. Race at least two hare scrambles this summer. - Done! I raced 9 out 10 District 16 hare scramble events this summer. I raced in the B class and was a mid-pack finisher throughout the season. It was a ton of fun, challenging, and an incredibly enjoyable way to spend the weekends. Overall, I was pleased with my performance but see a lot of room for improvement. The main issue I have is that my stamina is lacking. Due to having knee surgery late in 2017, racing in 2018 is likely off the table so I've got a lot of work to do to get back in shape for the 2019 racing season.
5. Complete the CAD modeling of last year’s two-stroke engine concept. - This one didn't happen. I've got a preliminary design for a new crank mechanism, but have not allocated the necessary time and energy to make this a reality.
6. Finish annihilating the invasive species called Buckthorn that has populated my land like horny rabbits and get our apple orchard going. - I decided to go racing instead, then had knee surgery. Didn't happen. Maybe I'll buy some goats and let them chew it all down (my animal-loving girlfriend is very fond of this solution).
7. Finish roughing in and laying out my track/trail on my property. - I didn't put much energy into this one either apart from maintaining what I already have.
8. Read 12 books. - I got through four in full. I did start several others and have left them in various places. Plus, I read my two-stroke book more times than I care to recall during the editing process... so does that count for the remaining 8 books?
Overall, 2017 was a good year despite not hitting all my goals. What I've started to notice is that my interests are becoming more widespread and I'm having a harder time focusing on one or two major goals for the year. I also sunk a lot of energy into my 9-5 job where I received a promotion and became the head of the engineering department. This has been a good change, but has sucked a lot out of me and I'm still trying to strike a balance so that I can get things done in my free time.
Looking Ahead To 2018
In 2018 I plan on setting the bar high and tackling a diverse set of goals. I'm going to continue working on striking a balance between my day job and the rest of my life. I plan on continuing to write and publish helpful content to DIY Moto Fix so that our sport remains accessible and affordable. I've also got a lot of projects of personal interest to me that I want to tackle. Here's what I'd like to get done in 2018:
1. Write and post to DIY Moto Fix monthly to keep quality content coming for you guys.
2. Fully rehab from knee surgery and in turn, come back to racing stronger than before.
3. Build the standing desk I've been designing the last few months to make working on the computer a lot more enjoyable and comfortable.
4. Learn how to become reasonably good at machining so I can be more self sufficient in the garage and execute my own designs.
5. Complete the CAD for my two-stroke engine design.
6. Prep the bike for the 2019 racing season.
7. Read 6 books.
Have you had a chance to think about the new year? What goals are you planning on setting for yourself? Leave a comment below and share them! Thanks and have a great year!
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
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.
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.
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!
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:
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!
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This week I want to talk about two-strokes. To kick off this post I have some awesome news. The Two Stroke Dirt Bike Engine Building Handbook is off to the printers and will be available for pre-sale very soon! Getting the book off the ground has been no cake walk. It's been two years coming and we are so thankful our riders and fans have been patient with us! At the end of this post I'll give you instructions on how you can stay updated on the launch. With that said, let's get started. Today's post aims to provide an overview of the important aspects of the two-stroke cylinder and answers a couple commonly asked questions relating to cylinder modifications.
Today I want to share some pointers on preparing new or re-plated cylinders that will help ensure your engines run stronger and last longer. Plus, I've got an update on the two-stroke book I've been working on that I'd like to share. Let's get started!
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