A Transmission is defined as a mechanical assembly (machine) that transmits power from the Engine to the Final Drive. The simplest transmissions can have just one, fixed ratio and no shifting. This article will expose the detailed workings of the 6-speed motorcycle transmission, but the 4 and 5 speeds work the same way.
Power is applied to the Input Shaft (pinion/drive shaft) of the transmission by the Clutch when it is engaged (plates and disc sandwiched together) and the Engine is running. The input/drive shaft turns anytime and all the time that the clutch is engaged. There is a drive/pinion gear for each ratio (gear change).
The input shaft gears mesh with their corresponding Driven Gears that ride on the Output/Driven Shaft. Motorcycles use Constant Mesh type transmissions. This name comes from the fact that the “gear pairs” are always meshed. These gear Sets/Pairs provide the gearing ratio changes that we use to go from stand-still to top speed, and in our case a high transmission ratio of 3.1:1 for our 1st gear and 0.8:1 for our 6th gear.
The 3.1:1 Ratio of 1st means that the Input Shaft must make 3.1 revolutions for every 1 revolution of the Output Shaft (shaft where the front sprocket attaches).
The 0.8:1 Ratio of 6th means that just .8 revolutions of the Input Shaft results in 1 full revolution of the Output Shaft.
Some of the gears in our transmission are keyed/splined to the shafts they ride on and some spin freely. No two gear “Pairs” can be locked-in at the same time. Doing so would have disastrous results since they would each try to turn the output shaft at different speeds. The job of motorcycle gear shifting falls on the Shift Forks and Shift Drum to ensure that absolute control and placement of the splined gears be precise and properly timed.
The Shift Drum has “worm channels” cast or machined into the surface. These channels provide and manage the directional control for each of the Shift Forks. As the Drum rotates, the channels hold or move the Forks right or left to engage and disengage the different splined gear sets.
The Shift Drum moves in a rotational manner, but never a full 360 degrees. The Drum is limited and rotation stopped at it’s lowest and it’s highest positions (usually 1st, but some motorcycles do have Neutral at the bottom and some at the top). Neutral is achieved when all gear pairs are unlocked and the Output/Driven shaft is not powered. Most Neutrals are now designed between 1st and 2nd.
The Shift Drum has the mechanical Stop for a reason. If allowed to continue rotating, the shift forks would lock-in 1st gear immediately after 5th or 6th – locking the tire, damaging the transmission, and over-speeding the engine – all of which could have catastrophic results. For that reason, Shift Drums have the rotational limits built-in. While Neutral could be designed to fall between every gear change, that function would be undesirable and a real nuisance. The choice to have it closest to and in-between the gear change/selection most used when starting off fell squarely between 1st and 2nd Gears.
The Shift Drum is rotated forward and backward by a “ratchet” system, When your foot presses down on the shifter pedal, the Shifter Shaft is rotated and the Ratchet tooth pulls on the Shifter Drum Pins to rotate the Drum by one Detent. Only when the shifter pedal is released does the ratchet move back and is set to move the Drum again. The travel of the ratchet is limited to only 1 pin/detent move. This same ratchet action is used when the shifter pedal is pulled upward by the foot. The Ratchet tooth then pushes the Shift Drum Pins to rotate the Drum by one detent. It is this “press/release” Ratcheting action that keeps us from making more than 1 Gear Ratio Change at the time. 1-N-2-3-4-5-6 and 6-5-4-3-2-N-1.
The precise rotation and positioning of the Shift Drum is controlled by the Shift Detent Roller/Spring assembly. This spring-loaded roller rides on a cam assembly that maintains “next gear only” control and prevents the catastrophic results if 2 pairs were to be engaged at once. I think of this one device/mechanism as the single most important part of the entire engine/transmission assembly – without it, failure is immediate and certain.
Join us next time and we’ll take a detailed look at Clutch Design, the Components, and How They Work.
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Rumors have it that Kawasaki kept pushing the envelope in performance and then in 2035, the H222 finally exceeded Warp. The daring rider who was willing to test anything with an Electron Dynamo Fusion Engine was given the nickname “Warp” and sadly never seen or heard from again. In a twist of fate, the rider was thrust back in time – 75 Million Years Back!
Turning the DR Into a Mini Adventure Bike series will focus on the Changes and Improvements made to my 2013 DR650 after a full Summer of testing and our full-gear TAT Trial. My mission…..still very still clear – build a purpose bike on the Cheap. This segment will spill-over into Performance and how to make your DR more enjoyable.
With a Jet Kit and tuning, the carburetor performance was improved on the stock BST vacuum carb. Improved means it would now idle and was a lot easier to start. I wanted more. Off-idle grunt and tight maneuvering response was still poor – No let’s make that Lame. The problem? That big vacuum carburetor was still delivering soggy low-end performance and it took seconds for the vacuum slide and needle jet to actually settle down and feed the “right mix” every time you whacked the throttle open.
During the Summer before our TAT Trial, we spent weekends riding Fire Roads and Logging Trails in the North / South Carolinas and Tennessee to include 2 extended camping trips where we could test set-ups. The goal was to ride hard and ride fast to see where we and the machines might break.
The Crash – Poor judgment of speed and throttle on my part resulted in a fast low-side crash on the DR in a blind right-handed turn at the top of a hill. The sand covered hard-pack dirt wasn’t going to let my tires take any bite.
The right side Pelican box came up and off of the lower rack mount. The tubular rack would in fact support the weight of the Pelican box fine and did secure the boxes under normal conditions, but my crash proved that I had to limit movement upward. I have to say that I was very impressed with the Pelican box and just how well it took the impact. Same for the Wolfman Racks I use to support them. The flaw was in the way I did the bottom support. It was a simple “rest on” support and did not stop or limit upward movement. Instead, it relied on the bolts at the top of the Pelicans to do that – something they were not up to task for.
The solution was to add the Aluminum Wolfman Rotopax plates to each side loop and then cut/slot reliefs that allow the bottom Pelican mounts to work as before, only now they would Prevent the bottom supports coming up during a low side impact. The “win-win-win” was that they would add loop rigidity, prevent the Pelican box movement, and provide for RotoPax mounting where/when Fuel/Water was needed – all while being very light in weight.
The long skid on the hard dirt road proved that hand guards, AKA “Bark Busters” are worth their weight in gold. My bars, levers, and guards came through the crash perfectly. The ones I installed are Tusk brand and include a small plastic hand shield that does wonders for keeping brush and limbs off your fingers as well as help with cold and wet. These also have the built-in LED‘s for turn signals that do make the bike more visible on the sections of highway we have to travel to get to our favorite off-road track. I did have to modify my stock levers to fit within the travel of the hand guards which was little more than cutting and sanding the ends of the levers off.
The crash demonstrated that the brake (foot) pedal was vulnerable during a drop. The bike went down and skidded on it’s right side – the brake pedal was pushed hard into the right hand crankcase, leaving a deep scratch. Had the pedal hit pavement, a root, or been hung-up by thick grass, I think the pedal could have perforated the right crankcase cover and compromised the oil supply. As was, I had a brake pedal that would not function. We had enough tools with us to pull the pedal out away from under the crankcase and allow me to use it on the limp back to camp.
The permanent fix for me was to inspect the stock case cover and determine the scratch was not a threat to long-term oil containment and to add one of the strong Stainless Steel covers available from ProCycle to the crankcase so that would never happen again. I also sourced a folding pedal from an 80’s model XR350 Honda and grafted the toe pad to a new Suzuki DR650 pedal (mine was trashed beyond service). I positioned the foot pad such that it would fold at a 45 degree angle – deflecting in either an upward (fall) or backward (forward impact), or both.
I would also add a lanyard cable between the aftermarket skidplate and the brake pedal. This lanyard serves to prevent limbs, brush, and roots from getting jammed between the frame and brake pedal and to limit the amount of travel in the event of a slide.
The long hours of riding proved that standing during those slower dirt sections was a critical part of covering the 10 hour days. I’m 6 foot in boots and the DR was too compact for me to do that comfortably. I came back from our TAT Trial and invented/built my first edition RRR Adjustable Handlebar Riser System. I also studied the ground clearance of the bike after all of the Suspension modifications and determined that the foot pegs could easily be lowered 1.5″. The combination of lowered pegs and higher bars would make those standing breaks a whole lot safer and easier. I would have more leverage (hands closer to the push-up position and I would not be slumped over trying to hold the bars).
Better yet, my RRR Adjustable Handlebar Riser System would solve the clearance problems with competitor designs.
For the foot pegs, I could not simply “lever” them down again as some of the bolt-on lowering brackets do. I wanted to remove as much of the stress (leverage) on the frame mounts as possible while achieving the lowered position – Cutting and Welding the foot pads onto a donor set of DR650 pegs purchased on eBay did that for me. I eliminated a lot of the leverage and stress and all of the height that the stock pegs place on the frame.
We used Roll Charts on the TAT Trial. Wow! I hadn’t done that much math since High School……. Every turn and every intersection, many of which are unmarked required a quick calculation between the odometer’s current mileage and the roll chart’s accumulating mileage for that section. Miss one calculation and you’ve lost the turn and screwed-up the consecutive turns and directions for the rest of the course. Forget GPS except to tell you where you are – they simply are not programmed to keep you on the longest, dirtiest, and off-road route possible and neither of us had one of those heavenly Enduro Counters.
All of this interaction with Odometer, Roll Chart, and the GPS made it perfectly clear – Those items needed to be immediately in front of your eyes. My RRR Adjustable Handlebar Riser would solve this need also. I would make Flat Caps and Dash Accessory mounts that could hold charge jacks and RAM Mounts so all of the navigation tools, and your camera could perch on top of the Steering Stem – thereby having the least amount of distortion and movement possible (versus out at the handlebar ends). This would keep business and the front wheel in the same direction of sight.
This will give us a stopping place for now. In the Part 3 Article, I will cover the Gear and Equipment that I’ve made/designed and purchased to “Gear Up” for Off-Road Survival.
Whether you’re looking to make a single item repair, to make repair to multiple components, or a full-on motorcycle restoration project start to finish, the Interactive Microfiche websites like the ones available through RonAyers.com and many others are a good way to get started.
For those of us riding and maintaining Honda, Kawasaki, Suzuki, and Yamaha motorcycles made over the last 40 + years, these Microfiche tools are outstanding.
They show year and model definition details with high accuracy and the part numbers that go into making each bike. Just a heads-up about using on-line microfiche though, a listing for a motorcycle part and it’s price detail for that part Does Not mean that the OEM part is available or that one exist in the world.
I’m a planner. I love taking projects of the worst kind and breaking them down into dozens of manageable pieces.
Microfiche pages have been a part of my process for many years.
I find the on-line microfiche that best covers the motorcycle in my project and I print out every page. I then bind those pages into a folder that I have in my workshop for constant access. During the teardown, I mark which parts I’m going to need to replace or find.
Sometimes on the older machines, OEM Parts are not available, but knowing the OEM Part number, how many are used, and exactly where they go in the assembly can help us find them through eBay and other selling resources.
Using the “where used” feature of the microfiche website has led me to salvaged parts of the correct part number from different years/models that could be restored for use. As I order and later receive each part, I document that onto the microfiche page.
Microfiche pages are usually drawn and grouped into assemblies of related parts.
These assemblies can guide the new restorer or mechanic through each segment of the repair. As mentioned earlier, the microfiche page is a good tool for keeping record of parts ordered, parts received, and parts used during assembly. They go from being a planning tool to an assembly tool, then onto a recorded tool for each/every bike I’ve restored.
Make friends with your favorite Microfiche website for motorcycle parts and be sure to use the OEM Parts Tool on your next motorcycle repair or motorcycle restoration project.
The M203 TPMS Display is easily installed on your dash, fairing, handlebar, brake reservoir, and many other convenient locations. The sensors replace your valve stems and go inside your rim like the millions installed on today’s automobiles.
Internal mounting of the sensor keeps it protected from the elements plus gives it the unique ability to Monitor and Warn you should either Pressure or Temperature threaten your Front or Rear Tire. Those other Cap-type, screw-on sensors rely on air that must come through the Schrader valve and actually compromises the valve’s seal.
The Cap-types have limited space and function due to their smaller size. Smaller batteries, smaller transmitters, and they can’t accurately measure the temperatures of your tires. If you’ve ever wondered why every automobile manufacturer puts them inside the rim and not on the stem, you know it – so don’t compromise. Get one of our Orange Electronic TPMSystems for your bike
The Installation on the Super Tenere did require one small modification to the rear rim. As shown in these images, the U Shaped relief for the stock, rubber valve stem is not wide enough for our M203 Sensor’s metal valve stem. We used a small file to add a few millimeters of clearance for the lock nut and socket that we used to apply the required 35 inch pounds of tightening torque.
For the Display, all you need is 12 Volts to power the Digital Display and operate the receiver. You’ll want the source to be switched so the the display monitor operates only when the ignition key is switched On or to Accessory Mode. To make those connections, you can tap in with the supplied taps or make your own “plug-n-play” connection using Hitachi connectors like the ones shown. These are available at www.vintageconnections.com and many other wiring specialty stores.
• Tire Pressure Warnings – Display Screen turns Red to Alert you Immediately if/when Pressures drop below your Preset limits
• Tire Temperature Readings Front and Rear Simultaneously (programmable F/C and accurate to within 4 Degrees)
• Tire Temperature Warning – Display Screen turns Red to Alert you Immediately if/when Temperatures exceed your Preset Limits
• Motorcycle Battery Voltage – Display Shows Motorcycle Voltage Allowing You to Check Your Bike’s Battery and Charging System’s Heath at a Glance
• Motorcycle Battery System Warning – Display Screen turns Red to Alert you immediately if/when the Bike’s Voltage drops below 11 Volts
• TPMS Sensors Voltage – Display Shows you the Voltage of Front and Rear Each Tire Sensor’s 3-Year Battery
• Safe and Secure In-Tire Sensor Mounting
• Quick, Easy Display Mounting using the Supplied 3M Velcro Pads
• 12 Months Warranty and No Fuss Replacement standard. Register on our Site and get an additional 12 Months Warranty.
Why this Tire Stuff? It’s important. I started RRR because I wanted to make a difference – to build, sell, and market what is the best Roadside/Trailside tool roll kit available. An abbreviation for Repair, Roll (roll your tools), and Ride, RRR Tool Solutions still makes and distributes it’s core product – the 46 Piece Adventure Tool Roll Kit, but we’ve got a lot more. Read on and let’s get into what I know about Tire Maintenance and TPMS. When you’re done reading, have a look at our other pages, products, articles, facts, stories, and send your comments.
While motorcycle tires have the same job as those on your car or truck, they do it very differently. Our motorcycles lean to turn thereby moving the center of gravity inward so the weight and inertia are transferred to the road at an angle, or “Camber Force”. Your car/truck tire supports the weight downward and the inertia to the side with “Lateral Force“. The job and method are as different as the shape of the two tires.
The rounded shape of the motorcycle tire serves two important functions –
First it is designed for the lean – keeping it’s contact patch and shape constant throughout changing lean angles.
Second is the movement right and left that a tire leaned over is going to give. I used one of my 170/60/17 tires to demonstrate. Measured at the very center of the tire, the measurement around this tire was 78.6″. So in one revolution, the bike would move 78.6″. Now, measured at the sides, the same tire has a measurement of 66″ -a full 12.6″ difference. Looking at the ice cream cone, we know that when rolled on a table or countertop, the cone will move sharply left or right depending on which way we roll it. Let’s get on the bike now and get it leaned sharply into a right-handed turn – the center of the tire is 78.6″ and the edge of the tire is 66″, so our entire bike is going to move right with every turn. The round shape of the motorcycle tire is what makes this side movement front and rear possible and unlike our car/truck tire that has to point and roll in the direction of the turn.
Correct Tire Pressure. How do we monitor and assure ourselves that our tires can do their job? TPMS
This roundness is great, right? Well for turning, Yes. For mileage and longevity, No. Because our motorcycle tire is rounded, the amount of tire in contact with the road is relatively small when going straight as compared to a car/truck tire of the same total width.
Ok, so we learned why the shapes are different and now realize that the smaller running surface of the motorcycle tire is why our mileage is less. It doesn’t stop here though. The rubber compounds used in motorcycle tires are often much softer/stickier than those of cars/trucks. Softer/stickier tires raise the coefficient of drag by increasing the amount of surface contact. They do this by deforming to the road surface irregularities easier, faster, and with less force required than harder rubber. The downside is that softer rubber tears and shreds itself away as it moves across those road surfaces. The more friction, the more tearing and shredding of the rubber.
Heat and Soft Rubber also have a direct relationship. Cold rubber will be harder, less sticky, and less willing to conform to the road surface irregularities thus less grip. Hot rubber is too soft and looses it’s ability to hold onto road surfaces as it should and must do. Tire Flex is the major source of heat in a tire used in normal conditions. The flexing will generate heat through the carcass movements. Tire manufacturing companies have spent years developing and testing different tire compounds and construction methods. These tires are made and designed to work at very precise pressures.
TPMS. How do we monitor our pressure and tire temperatures? TPMS
Rubber is an organic substance so a tire starts decomposing the day it’s made. Time, Sunlight, and Heat all take their toll on our tires. Whether they’re on the motorcycle or in storage, the moisture naturally present in the rubber when new out-gases and the tire turns drier, harder, and closer to compost every day. As they dry and age, tires become brittle and less able to handle the stresses of flexing and use. Be aware of this and look at the dates carefully before you jump on that great close-out pricing. Fresh Rubber, proper sizing, and proper inflation are key to safely enjoying our sport.