by JohnNicholas on 12/23/2009
Carburetor tuning has the greatest effect on engine performance. When a motorcycle manufacturer builds a bike, they usually install jets in the carb that are too rich. The manufacturers sell the same model worldwide, so they couldn’t afford to install different jets in the carb to suit all the different climates and types of fuel. In addition to the climate and fuel, the manufacturer would also have to consider many other factors, such as the terrain and type of riding. And then there is the most important jetting consideration, the rider.
When I worked as a mechanic, I was in charge of jetting the bike over the course of the day. During morning practice sessions, the track was usually muddy and the air temperature was at its lowest point. I had to jet the bike rich for practice because the air density was
by Charles Owens on 12/20/2010
What Is Final Drive Ratio: The final drive ratio can be calculated by dividing the number of teeth on the rear motorcycle sprockets by the number of teeth on the front or countershaft sprocket. For an off-road dirt bike the result will typically range from approximately 3.5 to 4.5. This number represents how many times the countershaft sprocket will turn in order to turn the rear motorcycle wheel one revolution. A higher number equates to more turns of the countershaft sprocket and is referred to as “Lower Gearing”. Conversely, a smaller number is referred to as “”Taller Gearing”.
by JohnNicholas on 12/15/2008
Do you have a modern two stroke Honda, Kawaski or Suzuki? Do you want to update the handling of your bike to modern aluminum framed standards?
Well MPS (Motorsports Products and Services) just may have the perfect answer for you.
by JohnNicholas on 12/04/2009
If your like me, when you see these works of art, these machines built from parts you wonder, just how the hell did they do that!
The following pdf file will show you how Benny Lindberg built his own Aluminum framed wonder. Please keep in mind that English is not Benny’s first language, so some sentences may need a little thinking about, but he writes very well and goes into detail on what is required to build one yourself.
by Charles Owens on 11/28/2012
Clutch Removal And Installation
This information is good for most motocross and off-road applications.
by JohnNicholas on 10/21/2009
Looking for a bit more power from your KTM 250 SX? KTM has the answer for you. An engine kit that bolts right on to your existing bike that increases the displacement to 300cc.
This kit is perfect for the vet motocross racer that wants a little more power out of their machine.
by JohnNicholas on 10/13/2009
This article was written by Phil Mickelson at Snow Goer magazine. More in-depth information about fuel injection on two-strokes. While these are not motocross applications you can see how they could be adapted to MX bikes.
When U.S. Environmental Protection Agency regulations for snowmobiles started in 2006, Ski-Doo already had its 600 H.O. SDI two-stroke engine on the snow for two years. It was considerably cleaner than regulations required and it achieved industry-leading fuel economy. The engine was light, powerful, dependable and clean.
by Charles Owens on 10/11/2012
2-Stroke Tech: Are you checking your ring end gap?
Why is end gap important on my 2-stroke? Proper end gap assures that the ring can operate correctly, and has enough room to expand from heat, and not bind on the piston locating pin or in the cylinder bore – this is the result of too tight an end gap. On a 2-stroke, too loose is less of a problem, to a point. Excessive end gap is an indication of a worn ring and cylinder bore, at which point it is a good time to look at replacing any worn parts in the system to bring everything back into proper tolerance. In the first picture, you will see a cylinder and piston kit, along with the minimum tools that you should have to measure ring end gap. The calipers are optional, but at very least you will need a good set of feeler gauges and a calculator.
by JohnNicholas on 09/24/2010
The basic explanation of how the internal combustion engine works, is the process of SUCK-SQUEEZE-BANG-BLOW. Simple explanation for a somewhat complex marvel of mechanical ingenuity .
One this site we have mentioned the four-stroke started off SUCKING and we’re right! They do SUCK before anything else.
by Charles Owens on 09/08/2011
What happens when a GM Field Engineer with a passion for High Performance Two Strokes wants more power? You got it; he develops his own Port Fuel Injection System.
Over the past few years, Richard Bruckner from High Gain Tuning has been sharing his vast knowledge of Direct & Port Fuel Injection systems with his two stroke fan base. Richard is an expert in the field having worked as an engineer for General Motors. His expertise in fuel injection, over 31 years worth has gathered the attention of many two stroke Powersports enthusiasts. When it comes to engine management, fuel injection is his passion.
by Charles Owens on 08/23/2012
by Big Bore Maico on 08/19/2008
I hope everyone who reads these pages can take something from them that makes their dirt biking more fun, with less hassle and expense.
I’d like to start out with the definition of a word. POTENTIAL. The definition of the word is as follows; existing in possibility, capable of development into actuality! The reason I started here is because motorcycles have potential. Potential to have fun, and also to hurt and kill you. So we must understand the risks involved in whatever endeavor we wish, particularly when a helmet is required. So in dirt biking, we have, existing in possibility, the capability to ACTUALLY HAVE FUN. There are various and sundry reasons why we don’t have fun, as that potential is there as well. So with that frame of reference in mind, let’s start.
by Charles Owens on 07/23/2011
by JohnNicholas on 06/30/2010
When someone says they can run their two stroke at 200:1 the first thing that happens is that people’s eyes go wide and they say “Huh?” It happens every time the Project Two 50 team mentions they are running a 200:1 mixture. Of course there are many that are skeptical.
How can anyone possibly use such a lean fuel/oil mixture?
by Charles Owens on 05/18/2012
This is a general motocross bike maintenance article. If you have a Two Stroke (which you should) skip the Four Stroke tips. If you have a Four Stroke skip the 2T tips.
Carnage every where. You see it every week at the track.
by Charles Owens on 05/01/2013
The Gatekeepers of Power
by Charles Owens on 03/29/2013
Technical Product Focus: Boyesen Power X-Wing
The Relationship Between Air Velocity and Engine Performance
by dogger315 on 03/29/2010
This is part nine and the final part of the CR250 engine build and will cover head, reed valve and carburetor installation. I will also perform the initial leak down test.
Tools needed: Torque wrench, leak down tester, metric tool assortment
by dogger315 on 03/20/2010
This segment will cover piston, rings and cylinder installation and power valve adjustment.
Tools required: Torque adapter, torque wrench, standard assortment of metric tools.
by dogger315 on 03/16/2010
Part seven of the CR250 engine build. Now that the bottom end is done, we can turn our attention to the top end. Top end segments include, cylinder and cylinder head prep, power valve installation and set-up, piston and rings, reed valve and carburetor.
This segment will cover power (or exhaust) valve installation.
by dogger315 on 03/12/2010
by dogger315 on 03/08/2010
Part five of the CR250 engine build. This segment will cover the installation of the clutch pack, right side cover, power valve governor and water pump cover.
Before installing the power valve governor, coat the throwout balls and the rack with a 50/50 mixture of moly 60 grease and transmission oil. Place the 12mm plain washers on each end of the governor. Align the rack yoke with the bearing race on the governor and install as a unit in the right side center case.
by dogger315 on 02/27/2010
This is part four of the CR250 engine build and will cover the assembly and installation of the kickstarter, idle wheel and gear change mechanism.
To assemble the shift pawls and springs, coat the springs, plungers and pawls with transmission oil. Insert the pieces into the shifter and place the completed assembly into the plate guide. Place the assembly aside.
by dogger315 on 02/16/2010
Part three of the CR250 engine build. This installment covers combining the two center cases, installing the seals, clutch lifter lever and primary gear.
Tools needed: Case splitter or crankshaft installer/remover, engine stand, torque wrench and standard metric tool set.
by dogger315 on 02/11/2010
In part two of the CR250 engine build we will cover crankshaft, transmission and gear shift components.
Tools you will need: crankshaft installer/remover, engine stand, service manual, circlip pliers and a typical metric tool assortment
by dogger315 on 02/10/2010
This is part one of a nine part series documenting the assembly of a Honda CR250 engine.
Round one includes the center cases and right side case cover.
by Charles Owens on 01/19/2012
Top-end rebuilding is the most frequent and costly service routine on two-stroke dirt bikes. Every year, dirt bike riders waste loads of money on top-end parts that didn’t need to be replaced, or make costly mistakes while performing repairs. This section will give you the dos and don’ts to easy top-end rebuilding, plus some tips that aren’t printed in your factory service manual.
Before You Start
by Charles Owens on 01/05/2011
The majority of off-road motorcycles have poor overall chassis setup.
One of the major differences between a beginner’s bike and a factory rider’s bike is the experience & knowledge of the person performing the setup. Unfortunately many riders just ride their bikes with no thought of chassis setup, and only do the bare minimum required maintenance. This is unfortunate as not only will the bike’s performance and your enjoyment of the sport suffer, but having the proper setup offers enormous advantages in SAFETY!!