OK... admittedly this is a very broad topic and I wasn't quite sure where to put it, so I stuck it in the Engines section because it's my intention to make this more of a technical type of article and also because I'm going to be talking mainly about engines.
I was reading a blog post from a friend of mine and it really struck a chord with me. It seems that the café racer genre has really taken off these past few years, but a lot of the newcomers seem to be missing some of the basics. They're immediately drawn to the looks of the café racer, but are perhaps not understanding the function (or even that the form follows the function). Now don't get me wrong... I'm not hating on the guys. Fresh faces are what will keep this knowledge alive and well in the years to come, but only if the knowledge is taught and understood.
Please allow me to repost the blog before we go too much further:
[quote author=kopcicle]What is a "Cafe Racer"?
Make it go ...
We all know that there are gains to be had just in the fine details without resorting to pistons , compression , valves , cams , extensive porting , carburetor and exhaust . Well , no , wait . Within reason and budget that is the idea !
Make it stop ...
Disc upgrade or pursue a lost art in tuning up drum brakes .
Make it turn ...
Make what you have the best it can be or bin it and adapt a modern front end entire.
Make it look ...
Like it's more at home carving corners than sitting outside the favorite pub .
Take pride ...
In the fact that each sub assembly is the very best that you can do with the tools , talent , time and budget available .Only then will the bike reflect that it is more than the sum total of it's parts .
Teach ...
What you learn . Without this not only the lesson but the spirit of the lesson dies with you .
Enjoy ...
What you do , what you build , what you ride .
Our bikes are not only a form of personal expression but a loosely defined art form that stems from the enthusiasts of previous decades . Without growth and change we stagnate and die . In a world of posing and posturing for the benefit of who knows who what is the point of modifying a bike to be just like whatever unless it's meant to be a replica . Be original . Be different . Experiment . Let function be your guide and form will follow .
Our legacy to the next generation of riders and builders is our collective and individual vision . Our passion for that something extra defines our enthusiasm . Our ability to communicate and teach how to learn is our obligation . The definition of a "cafe racer" isn't rooted in our collective or individual past it will be defined by what we choose to do in the future . I've never known a brighter future for the genre in all my years turning a wrench . I can't wait to see what happens next .[/quote]
Now one other thing... there's a been more than a little drama on forums recently and I think one lesson we could all take away from it is that "you catch more flies with honey than you will with vinegar". That is, maintain a positive attitude. Instead of telling someone what they're doing wrong, tell them what they can do right. TEACH them right and wrong so that they can identify it for themselves. Be aware that sometimes there is more than one way to be right, but also be aware that there is almost always one BEST way.
With these things in mind, I'd like to get back to the main topic of this post. "Make it go". My own personal philosophy about café racers can be boiled down to two concepts.
1.) Form follow function - It has to work well first, look good second. Generally speaking, if it works well, it will look good.
2.) Built not bought - It's easy to take this maxim to an extreme, so please use this in the more moderate sense. It's your bike, you need to understand what's going on with it. If something breaks or there's something you want to improve, try it yourself. It may cost you some extra parts when you screw it up, but you've learned something in the process and knowledge is priceless.
Now that the preamble is over. Lets get down to it. This article is an attempt to pass on a bit of the knowledge I've gathered over the past few years. Undoubtedly, there are guys here with a lot more experience and a lot more knowledge than I and I welcome them to please correct me where I'm wrong and chime in with additions where applicable. I readily admit that most of my knowledge comes from reading and studying rather than doing and so keep that in mind. As always, empirical data trumps rhetoric. Something tested, measured, and replicated is something proven. Something written is just words on a screen. If you disagree with something I've said, please post why so we can all learn from it.
A café racer without performance enhancements is just a tractor with a body kit. Do you really want to be one of those kids in a 1.6L Honda Civic with glowing lights under the body panels racing his gutless wonder from stoplight to stoplight? If the answer is, "yes", you can probably stop reading now.
Seriously though, the engine is the heart and soul of your bike and I'm seeing fewer and fewer builds that attempt to improve this key component. I'm not sure why this is, but I suspect that our culture has come to favor looks over performance or perhaps people are a little wary of cracking open something that has so many parts? Cost is also a consideration, but if you can afford to drop $500 on fiberglass seats and tanks and another couple of hundred on paint and upholstery, a bit of money for the engine doesn't seem out of line, right?
Building an engine can most certainly be done in stages, but the most important thing to keep in mind is to take a holistic approach. There are few things you can change that won't also have an effect on something else. Understand the consequences (both good and bad) of each action before you take it. Not all parts will work in all circumstances and the final goal of your engine build SHOULD be the deciding factor of which parts go into it. Building a comfortable long distance cruiser versus building a café racer is more than just adjusting the seat and control locations. The engine characteristics are the soul of a bike.
So what are engine characteristics and how does the design of the engine affect them? Well... put simply, the characteristics of the engine can be categorized by the throttle response, revs, acceleration, torque and a host of even more subjective items. The engine from a semi truck can put out more than 600 horsepower, but you're never going to find one in a sports car (size issues aside). Sports car drivers want high revs. The very successful Honda S2000 can redline at 9,000 RPM. Much higher than most passenger vehicles. That redline is necessary to create an appropriate feel and power for the vehicle's purpose and equal thought should be given to your own engine.
There is something intangible to engine characteristics, though. How much of a grin is on your face after your bike pushes you through a tight corner? Is your bike still egging you on for more throttle even when you're skirting the ton? Or is your bike telling you it's had enough when you start pushing 80? The engine on a café bike should pull strong through the mid range and get even better as the rpms climb. The engine on a café bike should bounce off of the redline after a gear change and actually feel a bit sad that you didn't take it further. The engine on a café bike wants nothing more than to rev itself to pieces. It would love the opportunity to see how fast it can spin before parts start flying out. Is your bike screaming for more or is it screaming "enough"? Your engine should be willing and your bike should be braver than you are. Remember, café racers started out at street legal race replicas, mimicking the race bikes of their time. Would your bike be at home on a race track or did you just build another tractor with a body kit?
So... enough rhetoric already.
Time for some theory. I'll get into more details in subsequent posts, but for the remainder of this post I'm going to talk about the four general ways in which engine performance can be improved. Before that, though, lets talk about a few engine basics just to make sure we're all on the same page.
The Workings of a Four Cycle Internal Combustion Engine (ICE)
This may seem a bit basic to many of you, but I'm of the mind that a decent house needs a decent foundation and so I've included the info here.
An ICE is basically a self-powered air pump. Fuel and air is drawn into each cylinder, compressed, ignited/combusted, and then expelled. Repeat as frequently as possible. Those four steps are as follows:
Intake Stroke - Piston starts at Top Dead Center (TDC) and descends toward the crankshaft centerline. During the entirety of this stroke, the intake valve(s) remain open and the descending piston can be thought of in a similar manner to the plunger on a syringe, drawing fluid into it as it opens.
Compression Stroke - The piston ascends from Bottom Dead Center (BDC) back toward the head as the intake valve begins to close. The fuel/air mixture that was drawn into the cylinder during the intake stroke is now squished into a smaller and smaller volume.
Power Stroke - The compressed mixture is ignited with a spark from the plug and the ignition releases a great quantity of heat. This heat is what causes the gases in the cylinder to expand and produce an increase in pressure. This pressure pushes the piston back toward BDC. Partway down, the exhaust valve opens and begins bleeding excess pressure out the exhaust headers.
Exhaust Stroke - The piston passes BDC and heads back toward TDC. Going back to the syringe metaphor, this is the plunger being depressed and expelling all of the fluid back out of the syringe. During the entirety of this stroke, the exhaust valve remains open. The intake valve will open during this stroke as well.
An astute reader will have noticed that the piston descends and ascends twice for an entire period of the four cycles. This means the crankshaft is rotating 720° for each complete period.
How efficiently each of these four strokes can be accomplished is what determines the performance of your engine. These performance modifications will always go to serve one (or more) of four goals. These four goals are the same four goals for everyone, everywhere, and your modifications need to answer to these objectives.
The Four Goals of Engine Performance
1.) Increase Displacement - All things being equal, a bigger engine will outperform a smaller one.
2.) Increase Revs - Horsepower is a unit derived from torque. Torque is what is measured, horsepower is what is calculated. HP = (T x RPM) / 5252. If you can keep torque the same and increase your revs, you've just "created" horsepower.
3.) Parasitic Losses - The power generated by your engine goes into a lot more than just turning your rear wheel. It takes a lot of energy to spin metal as fast as your bike does and that's even without having to contend with friction of all the components necessary to make it happen. Reduce this friction and inertial losses and your engine will spin faster, sooner, and more of that power will make it to the ground.
4.) Brake Mean Effective Pressure (BMEP) - This is the average pressure within the cylinder, generated by the power stroke. More BMEP directly translates to more torque, which, of course, means more horsepower.
I'm right around my mental limit of typing for the day, so I'll go into more detail on each of the above four items in a later posts.
I was reading a blog post from a friend of mine and it really struck a chord with me. It seems that the café racer genre has really taken off these past few years, but a lot of the newcomers seem to be missing some of the basics. They're immediately drawn to the looks of the café racer, but are perhaps not understanding the function (or even that the form follows the function). Now don't get me wrong... I'm not hating on the guys. Fresh faces are what will keep this knowledge alive and well in the years to come, but only if the knowledge is taught and understood.
Please allow me to repost the blog before we go too much further:
[quote author=kopcicle]What is a "Cafe Racer"?
Make it go ...
We all know that there are gains to be had just in the fine details without resorting to pistons , compression , valves , cams , extensive porting , carburetor and exhaust . Well , no , wait . Within reason and budget that is the idea !
Make it stop ...
Disc upgrade or pursue a lost art in tuning up drum brakes .
Make it turn ...
Make what you have the best it can be or bin it and adapt a modern front end entire.
Make it look ...
Like it's more at home carving corners than sitting outside the favorite pub .
Take pride ...
In the fact that each sub assembly is the very best that you can do with the tools , talent , time and budget available .Only then will the bike reflect that it is more than the sum total of it's parts .
Teach ...
What you learn . Without this not only the lesson but the spirit of the lesson dies with you .
Enjoy ...
What you do , what you build , what you ride .
Our bikes are not only a form of personal expression but a loosely defined art form that stems from the enthusiasts of previous decades . Without growth and change we stagnate and die . In a world of posing and posturing for the benefit of who knows who what is the point of modifying a bike to be just like whatever unless it's meant to be a replica . Be original . Be different . Experiment . Let function be your guide and form will follow .
Our legacy to the next generation of riders and builders is our collective and individual vision . Our passion for that something extra defines our enthusiasm . Our ability to communicate and teach how to learn is our obligation . The definition of a "cafe racer" isn't rooted in our collective or individual past it will be defined by what we choose to do in the future . I've never known a brighter future for the genre in all my years turning a wrench . I can't wait to see what happens next .[/quote]
Now one other thing... there's a been more than a little drama on forums recently and I think one lesson we could all take away from it is that "you catch more flies with honey than you will with vinegar". That is, maintain a positive attitude. Instead of telling someone what they're doing wrong, tell them what they can do right. TEACH them right and wrong so that they can identify it for themselves. Be aware that sometimes there is more than one way to be right, but also be aware that there is almost always one BEST way.
With these things in mind, I'd like to get back to the main topic of this post. "Make it go". My own personal philosophy about café racers can be boiled down to two concepts.
1.) Form follow function - It has to work well first, look good second. Generally speaking, if it works well, it will look good.
2.) Built not bought - It's easy to take this maxim to an extreme, so please use this in the more moderate sense. It's your bike, you need to understand what's going on with it. If something breaks or there's something you want to improve, try it yourself. It may cost you some extra parts when you screw it up, but you've learned something in the process and knowledge is priceless.
Now that the preamble is over. Lets get down to it. This article is an attempt to pass on a bit of the knowledge I've gathered over the past few years. Undoubtedly, there are guys here with a lot more experience and a lot more knowledge than I and I welcome them to please correct me where I'm wrong and chime in with additions where applicable. I readily admit that most of my knowledge comes from reading and studying rather than doing and so keep that in mind. As always, empirical data trumps rhetoric. Something tested, measured, and replicated is something proven. Something written is just words on a screen. If you disagree with something I've said, please post why so we can all learn from it.
A café racer without performance enhancements is just a tractor with a body kit. Do you really want to be one of those kids in a 1.6L Honda Civic with glowing lights under the body panels racing his gutless wonder from stoplight to stoplight? If the answer is, "yes", you can probably stop reading now.
Seriously though, the engine is the heart and soul of your bike and I'm seeing fewer and fewer builds that attempt to improve this key component. I'm not sure why this is, but I suspect that our culture has come to favor looks over performance or perhaps people are a little wary of cracking open something that has so many parts? Cost is also a consideration, but if you can afford to drop $500 on fiberglass seats and tanks and another couple of hundred on paint and upholstery, a bit of money for the engine doesn't seem out of line, right?
Building an engine can most certainly be done in stages, but the most important thing to keep in mind is to take a holistic approach. There are few things you can change that won't also have an effect on something else. Understand the consequences (both good and bad) of each action before you take it. Not all parts will work in all circumstances and the final goal of your engine build SHOULD be the deciding factor of which parts go into it. Building a comfortable long distance cruiser versus building a café racer is more than just adjusting the seat and control locations. The engine characteristics are the soul of a bike.
So what are engine characteristics and how does the design of the engine affect them? Well... put simply, the characteristics of the engine can be categorized by the throttle response, revs, acceleration, torque and a host of even more subjective items. The engine from a semi truck can put out more than 600 horsepower, but you're never going to find one in a sports car (size issues aside). Sports car drivers want high revs. The very successful Honda S2000 can redline at 9,000 RPM. Much higher than most passenger vehicles. That redline is necessary to create an appropriate feel and power for the vehicle's purpose and equal thought should be given to your own engine.
There is something intangible to engine characteristics, though. How much of a grin is on your face after your bike pushes you through a tight corner? Is your bike still egging you on for more throttle even when you're skirting the ton? Or is your bike telling you it's had enough when you start pushing 80? The engine on a café bike should pull strong through the mid range and get even better as the rpms climb. The engine on a café bike should bounce off of the redline after a gear change and actually feel a bit sad that you didn't take it further. The engine on a café bike wants nothing more than to rev itself to pieces. It would love the opportunity to see how fast it can spin before parts start flying out. Is your bike screaming for more or is it screaming "enough"? Your engine should be willing and your bike should be braver than you are. Remember, café racers started out at street legal race replicas, mimicking the race bikes of their time. Would your bike be at home on a race track or did you just build another tractor with a body kit?
So... enough rhetoric already.
Time for some theory. I'll get into more details in subsequent posts, but for the remainder of this post I'm going to talk about the four general ways in which engine performance can be improved. Before that, though, lets talk about a few engine basics just to make sure we're all on the same page.
The Workings of a Four Cycle Internal Combustion Engine (ICE)
This may seem a bit basic to many of you, but I'm of the mind that a decent house needs a decent foundation and so I've included the info here.
An ICE is basically a self-powered air pump. Fuel and air is drawn into each cylinder, compressed, ignited/combusted, and then expelled. Repeat as frequently as possible. Those four steps are as follows:
Intake Stroke - Piston starts at Top Dead Center (TDC) and descends toward the crankshaft centerline. During the entirety of this stroke, the intake valve(s) remain open and the descending piston can be thought of in a similar manner to the plunger on a syringe, drawing fluid into it as it opens.
Compression Stroke - The piston ascends from Bottom Dead Center (BDC) back toward the head as the intake valve begins to close. The fuel/air mixture that was drawn into the cylinder during the intake stroke is now squished into a smaller and smaller volume.
Power Stroke - The compressed mixture is ignited with a spark from the plug and the ignition releases a great quantity of heat. This heat is what causes the gases in the cylinder to expand and produce an increase in pressure. This pressure pushes the piston back toward BDC. Partway down, the exhaust valve opens and begins bleeding excess pressure out the exhaust headers.
Exhaust Stroke - The piston passes BDC and heads back toward TDC. Going back to the syringe metaphor, this is the plunger being depressed and expelling all of the fluid back out of the syringe. During the entirety of this stroke, the exhaust valve remains open. The intake valve will open during this stroke as well.
An astute reader will have noticed that the piston descends and ascends twice for an entire period of the four cycles. This means the crankshaft is rotating 720° for each complete period.
How efficiently each of these four strokes can be accomplished is what determines the performance of your engine. These performance modifications will always go to serve one (or more) of four goals. These four goals are the same four goals for everyone, everywhere, and your modifications need to answer to these objectives.
The Four Goals of Engine Performance
1.) Increase Displacement - All things being equal, a bigger engine will outperform a smaller one.
2.) Increase Revs - Horsepower is a unit derived from torque. Torque is what is measured, horsepower is what is calculated. HP = (T x RPM) / 5252. If you can keep torque the same and increase your revs, you've just "created" horsepower.
3.) Parasitic Losses - The power generated by your engine goes into a lot more than just turning your rear wheel. It takes a lot of energy to spin metal as fast as your bike does and that's even without having to contend with friction of all the components necessary to make it happen. Reduce this friction and inertial losses and your engine will spin faster, sooner, and more of that power will make it to the ground.
4.) Brake Mean Effective Pressure (BMEP) - This is the average pressure within the cylinder, generated by the power stroke. More BMEP directly translates to more torque, which, of course, means more horsepower.
I'm right around my mental limit of typing for the day, so I'll go into more detail on each of the above four items in a later posts.