In this installment of "Tech Time" we will be looking at the different types of brake fluids used in motorcycle hydraulic brake and clutch systems. Let's first look at the function of brake fluid in a hydraulic brake system. Fluid that is free of air or gas bubbles is basically non-compressible. The master cylinder pumps (displaces) brake fluid through the brake lines to the caliper (slave cylinder) and forces the brake piston(s) outward where it applies force to the brake pads. The brake pads contact the brake disc, and slow the vehicle through sliding friction. This friction creates heat and that heat must also be dissipated by all the brake system parts and the brake fluid.

Next, let's look at the different types of brake fluid. The first type is DOT 3 fluid. This fluid is very common on automobiles and is a polyglycol ether based fluid. This fluid has a minimum dry boiling point of 401 degrees Fahrenheit and a minimum wet boiling point of 284 degrees F. This fluid is also hydroscopic (absorbs water). The second type is DOT 4 fluid. This is the most common fluid used in motorcycles and is also a polyglycol ether-based fluid, but it has borate ethers added to raise the boiling point of the fluid. DOT 4 has a minimum dry boiling point of 446 degrees F and a minimum wet boiling point of 311 degrees F, and is also hydroscopic and is compatible with Dot 3 fluid.

The third type of fluid is DOT 5 fluid. This fluid is silicone based and has a minimum dry boiling point of 500 degrees F and a minimum wet boiling point of 356 degrees F. This fluid is not hydroscopic (does not absorb water) and is not compatible with any polyglycol ether based fluids. The fourth type of fluid is relatively new and is called DOT 5.1. This is a polyglycol ether based fluid with synthetic additives and has a minimum dry boiling point of 518 degrees F and has a minimum wet boiling point of 375 degrees F. This fluid is commonly referred to as "Super DOT 4" fluid in automotive circles and is also hydroscopic. This fluid is compatible with DOT 3 and DOT 4 fluids, but is not compatible with DOT 5 fluid.

We will now look at wet and dry boiling points. The dry boiling point is at what temperature fluid that contains no water boils at. The wet boiling point is the temperature at which fluid with 3% water content boils. Polyglycol ether based fluids absorb water and keep it in suspension to protect metal brake system parts. As the dry/wet boiling point numbers indicate, water saturated fluid loses way over 100 degrees F of boiling point! Silicone fluid can't absorb water so as water collects in the system it stays separate and attacks metal brake system parts. This water can cause major braking performance issues because water boils at 212 degrees F! It is for this reason that silicone fluid needs to be replaced often. Polyglycol ether based fluids should be replaced every 2 years.

If brake fluid reaches its boiling point gas bubbles form in the fluid making it very compressible. It is at this point that brake feel becomes spongy or is completely lost, the results of which can be catastrophic! Hopefully this information clears up some of the confusion about brake fluids. Until next time, ride safe!

Viva Two-Strokes

I have to admit it: I'm an old-school two-stroke guy, I love the sound of a high-performance two stoke engine running "on the pipe." The comment that drives me absolutely nuts is "you know that they're outlawin' them two-strokes, ya know." My response to this is comment is usually to borrow a phrase from the TV show "Home Improvement" and say "I don't think so, Tim!" In this installment of "Tech Time" we will examine the two-stroke emissions situation, and while the motorcycle industry seems to be leaning away from two-strokes, we will look at other sections of the power sports industry to see that the two stoke engine is still alive and kicking!

The emissions situation for two-stroke engines is very interesting and misunderstood. The three things being monitored by the EPA are carbon monoxide (CO), hydrocarbons (HC), and oxides of nitrogen (NOX). Carbon monoxide is the principal product of combustion and is consistent in four-strokes and two-strokes. Hydrocarbons are basically unburned fuel molecules in the exhaust gas. This is the two stoke engines' biggest problem. Because the two-stroke engine has open ports in the cylinder walls and engine cycles that overlap some unburned fuel escapes out the exhaust port. The manufacturers have used semi direct and direct fuel injection to drastically reduce HC emissions. When you remove HC from two-stroke exhaust emissions you have a cleaner burning engine than a four-stroke! How can this be? Well the key is in the oxides of nitrogen. NOX is a product of combustion temperature, and being that combustion temperatures are lower in two-strokes, they have NOX emissions that are much lower than four-strokes. Although the EPA does not currently mandate low NOX emissions, some people believe future EPS emissions standards will include low NOX levels. If this happens, two-strokes will be very attractive to manufacturers because NOX is very expensive for manufacturers to remove from four-stroke exhaust emissions.

To prove this point we can look at the current happenings in the outboard boat motor business that is currently dominated by large four-stroke engines. Bombardier Recreational Products (BRP) currently offers direct injected two-stroke models that are the lightest, most powerful, and cleanest burning engines in the outboard business! Called E-TEC, these engines use direct injectors that mount to the cylinder heads that inject fuel into the combustion chamber after the exhaust port is closed by the rising piston. While not a new technology, it has been highly refined by BRP and won an EPA award for exceeding exhaust emissions standards. BRP is quickly gaining market share with these engines.

The snowmobile business is an interesting part of the power sports industry currently using two-stroke technology. While Yamaha has converted its models completely to four-stroke engines and has done a great job of making them as light as possible, they are still slightly heavier than competitors two-stroke models. BRP has a model lineup of primarily two-stroke models, some of which are semi direct injected, very fuel efficient, and emissions compliant. Artic Cat and Polaris are currently producing both two-stroke and four-stroke models that are emissions compliant. This business is very interesting because two companies are going in totally opposite directions and two companies are sitting in the middle ground.

Will two-stroke engines be common in motorcycles again? Current trends are leaning away from two-strokes, but if emissions standards change, two-strokes could be very attractive to manufacturers in the future. Only time will tell. When people ask me if I think that two-stroke engines will go away, I just say, "I don't think so, Tim!" Until next time, ride safe!

Fuel and Octane - Part Two

In this installment of "Tech Time" we will be examining fuel formulations past, present and where they might be headed in the future. In the "Good Old Days" there were two kinds of fuel, regular and premium (or ethyl). These fuels were of consistent quality, contained lead, and produced good power without detonation, life was good! The only problem was that lead is a harmful pollutant, so in the late seventies the EPA mandated that lead be eliminated from fuel. Many feared that the lack of lead in fuel would be harmful to valves and seats in four-stroke engines, but by this time most engines had hardened value faces, so this was only an issue with older vehicles. In the mid eighties the EPA mandated that fuel be "oxygenated." This was accomplished by adding an oxygen carrying agent (approximately 10%) to improve vehicle emissions. Two types of oxygenates were used, MTBE (an ether) and ethanol alcohol. MTBE had recently been phased out due to environmental concerns.

Some of the problems with ethanol are that it absorbs moisture from the atmosphere at a rapid rate, so much so that it cannot be transported via pipeline, so it must be hauled by tanker train or truck to the refinery for blending with petroleum fuel. Ethanol blended fuels have a very short shelf life, about three weeks. Ethanol also attacks fuel systems and leads to accelerated fuel system deterioration and filter clogging. Another problem with ethanol blended fuel is "phase separation." This occurs when the ethanol in the fuel absorbs enough moisture to become saturated. This saturated ethanol/water mix separates itself from the petroleum fuel. This is especially a problem with two-stroke machines that require pre-mix fuel.

Another fact about ethanol that you don't hear much about is that ethanol only has about 3/5 of the power producing energy that petroleum fuel has. In the case of E85 (85% ethanol/15% petroleum fuel) used in specially designed cars and trucks fuel mileage drops significantly compared to like vehicles using E10 fuel.

The state of Minnesota has currently introduced legislation that would replace the state's E10 fuel with E20, and 80% petroleum, 20% ethanol mix. This fuel would be harmful to most power sports products currently in use. Power sports organizations are watching this situation closely, as fuel system modification would be required to use this fuel.

Some suggestions for using today's fuel are to use fresh fuel all the time. On carbureted models drain carb float bowls after use if the machine is to sit idle for two weeks or more. Fuel injected models are more tolerant of these fuels. All of you two-stroke fans will not want to miss the next installment of "Tech Time" where we will be exploring the future of two-stroke technology, so don't miss "Viva Two-strokes" in next month's Tech Time. Until next time, ride safe!

Fuel and Octane: Part One

In this installment of Tech Time, we will be examining fuel and octane. Engines theoretically run on a mixture of approximately fourteen parts air to one part fuel by weight. The job of mixing the fuel and air is handled by either a carburetor or a fuel injection system. A carburetor is a passive device in that it meters fuel at a constant rate once it has properly calibrated. Changes in weather or engine condition cannot be compensated for without recalibration. A cold engine needs a rich fuel/air mixture in order to start, therefore carburetors are fitted with a choke that gives the engine a rich fuel/air mixture until the engine reaches operating temperature. A fuel injection system is an active system that constantly monitors engine perimeters and engine load and constantly adjusts the fuel/air mixture accordingly, as a result better operation and fuel mileage result.

Before we examine fuel and octane, we must first look at normal combustion, and abnormal combustion. The fuel/air mixture is ignited at a predetermined time before top dead center by the spark plug and the flame front burns outward from the spark plug until it reaches the piston edges thereby pushing the piston down, creating power. This is a "controlled burn" of the fuel/air mixture, not an "explosion". "Explosions" happen during abnormal combustion. There are two kinds of abnormal combustion, pre-ignition and detonation, whose causes are different, but the results of the piston, rod and crankshaft damage are very similar. Some people use the term "pre-detonation", this is a non-term and does not exist! Pre-ignition is caused by a hot spot or glowing carbon in the combustion chamber that ignites the fuel/air mix before the spark plug does and starts a flame front that collides with the flame front ignited by the spark plug and creates an abnormal pressure spike before the piston reaches top dead center. This shock wave is transmitted to the piston, rod and crank shaft. This will cause a "knocking" noise which if left uncorrected will lead to engine damage. Detonation is the other type of abnormal combustion where the fuel/air mixture simply self ignites before the spark plug ignites the fuel/air mix. This is caused by the fuels low octane level that cannot resist self igniting under the combustion chamber's heat and pressure.

That brings us to octane. Simply put, octane is the fuel's resistance to self ignite. The biggest misconception about fuel is that higher octane will get you more power. The truth is exactly the opposite! The higher the octane, the higher the resistance to detonate and the cooler the burn, conversely a lower octane fuel has less resistance to detonate and a hotter burn. The best performance (most power) in most engines is achieved by using the lowest octane fuel the engine will tolerate without detonating. The reason that high octane fuel is equated with higher output is that when the compression ratio is raised or the ignition timing is advanced, higher octane fuel must be used to control detonation. Fuel injection systems are fitted with sensors that detect detonation and retard ignition timing until the detonation is no longer detected, thus protecting the engine from damage if too low octane fuel is used. Until next time, ride safe!

Light'em up! Debunking Basic Ignitions

In this installation of Tech Time, we will be looking at basic ignition systems.

There are three basic types of ignitions systems used in most modern motorcycles today: Magneto Capacitor Discharge Ignition (CDI), DC Powered CDI (DC-CDI), and CD Powered TCI. These systems function similarly, but do have some differences between them.

Let's first look at the different ignition system components. The flywheel is a metal hub that is bolted to the crankshaft and contains strong magnets. A source (or charge) coil is a coil of wire wound around an iron core and fastened to the stator plate under the flywheel. A trigger (or pulse) coil is similar to the source coil only it is smaller and can be located inside or outside the flywheel. Both of these coils generate AC voltage as the flywheel rotates around them. The ignition coil comes in two basic types, external coil and stick coil. The external coil has a primary winding of heavy wire surrounded by a secondary winding of thin wire encased in a plastic molding. The coil also has a heavy gauge wire that exits the coil and goes to the spark plug cap. The stick coil integrates the coil, wire and spark plug cap into one unit and is very common on modern motorcycles. Both coils function like small electrical transformers. When the primary side winding is energized, it induces a high voltage in the secondary winding to cross the spark plug gap. The last part of the system is the control unit. The control unit controls timing and kill functions.

In the CDI system, the source coil produces AC voltage which is converted to CD and stored in the CDI box. When the flywheel reaches a predetermined position before top dead center, AC voltage is produced by the trigger coil is sent to the CDI box which then released the stored CD voltage to the coil that is then stepped up by the coil and discharged across the spark plug gap. The DC-CDI system functions the same, except it uses battery voltage (DC) for source voltage, so a source coil is not used.

The DC-TCI works the same as the DC-CDI system except the source voltage (DC) is supplied to the coil all the time and the ground side of the primary circuit of the coil is "switched" on and off by the TCI control unit to produce spark.

When troubleshooting these systems, coils must have continuity; they cannot be shorted to ground, and they must produce a specific amount of voltage. All wiring circuits and switches must be tested for continuity and shorts. There are usually no tests for control units, so if all the components test well, it can be assumed that the control unit is faulty. In the field, we find very few bad control units. Coil and switch failures are more common.

Until next time, ride safe!

Looking for Trouble

In this installment of Tech Time we will look at some basic engine trouble shooting techniques. Any time you try to troubleshoot a problem, a systematic approach must be used to eliminate the good components or systems and identify the faulty components or systems.

When troubleshooting a "no start" condition, an engine needs three basic things in order to run, spark, compression, and fuel (an air/fuel mixture). The first thing to do to troubleshoot a non-running engine is to remove the spark plug and verify that it is the correct plug for that make, year and model of motorcycle. Next, look at the spark plug's firing end. Is it dry or wet? A dry plug can indicate a fuel system or compression (engine) problem. A wet plug can indicate a fuel system or an ignition system problem. The most common problem is a fouled spark plug, so try replacing the plug with a new one and try to start the engine, if it starts the plug was fouled, if not continue troubleshooting. Next remove the spark plug and insert it into the spark plug cap and lay it on the cylinder head or any metal engine part and away from any fuel source. Next, turn over the engine while observing the firing end of the spark plug. A blue spark at the plug is normal; a yellow or orange spark is weak. We will be covering ignition troubleshooting in the future installment of Tech Time. One thing to remember is that on battery powered ignitions the ignition system needs a minimum amount of battery voltage to fire the plug, so the battery must be in good condition.

To check the engine compression, remove the spark plug and screw a good quality compression gauge into the spark plug hole. Also remove all the spark plugs on multi-cylinder engines. The throttle must be held wide open while cranking the engine until the gauge needle reaches its highest reading. Check the appropriate shop manual for the compression specs. If the pressure is low, then a leak down test will be needed to pinpoint the leakage point(s) in the combustion chamber (valves or rings).

If the spark and compression check is okay, then the fuel system will need to be inspected. First check the air inlet and air filter for blockages and clogging. If okay then the carburetor will need to be removed and inspected. Carburetor cleaning was covered in an earlier installment of Tech Time.

So the next time you are faced with a stubborn engine that will not start, just remember that it boils down to three simple things: spark, compression, and fuel. Until next time, ride safe!

Motorcycle Batteries 101

In this installment of Tech Time, we will take a look at batteries. They are probably the most misunderstood and neglected part of a motorcycle.

There are two basic types of batteries currently being used in motorcycles today: lead-acid batteries and absorbed glass mat (sealed) batteries. Let's first look at lead-acid batteries. They have translucent casings so that the fluid level can be inspected, and are vented to the atmosphere. When these batteries are initially activated, standard battery electrolyte with a specific gravity of 1.280 is added to each cell up to the full mark of the battery case. The battery then must set for 30 minutes to allow the electrolyte to fully soak into the lead plate material (bypassing this step will lead to plate erosion and premature battery failure) then top off level with electrolyte. Then the battery needs to be charged at 1/10th its amp-hour rating until the voltage reaches 12.8-13.0 volts. Using the battery (loading it) before being fully charged initially will limit the voltage capacity of the battery for its lifetime! Anytime the electrolyte level drops (it needs to be checked periodically!) add only distilled water, not tap water, as it contains minerals that can cause premature failure. These batteries also discharge at approximately 1% a day when sitting idle, so they must be trickle charged every 2-3 weeks when not in use. These batteries also need to be mounted snugly in their battery box as vibration causes plate damage (shorting) and premature failure. During off season storage, the battery needs to be removed from the motorcycle and charged once a month and fluid level topped off when low.

Next, let's look at sealed batteries. These batteries have a dark colored casing and use an electrolyte with a higher specific gravity (1.320). The electrolyte comes in a pre-measured container with the battery. This container is inserted into the top of the battery and fills the battery at a slower rate. This allows the electrolyte to be absorbed into the battery and forms a gel around the plates so there is no free standing fluid in the battery. The battery needs to sit for 30 minutes to complete this process. Because there is no fluid to leak out, these batteries can be mounted at any angle in the vehicle. After the soaking process the battery is permanently sealed for life. The battery then needs to be charged at 1/10th its amp-hour rating until the voltage reaches 13.0-13.5 volts. Using the battery before being fully charged will also limit its voltage capacity for life. These batteries also lose 1% of charge per day while sitting, so they need to be charged every 2-3 weeks of inactivity, they also need to be removed and charged once a month during off season storage. These batteries also need to be snugly mounted to avoid vibration damage.

A well serviced and maintained battery can easily last 4-5 riding seasons, until next time, ride safe!

There's a Fungus Among Us - Clean That Dirty Carb!

That's been a familiar expression in the shops I've worked at through the years. We use it when a neglected motorcycle is brought in for service with a "no-start condition," only to discover skunky, rotten fuel in the gas tank, and a mysterious green goo in the carburetor.

If you didn't follow Jim Durivage's winterizing tips (January 2007 Tech Time) you might be faced with the same problem when preparing your own bike for the upcoming riding season.

The mysterious green goo is actually a fungus that can grow in unstabilized, old fuel. As fuel sits, the volatile elements of petroleum evaporate, and the octane level drops considerably. When the octane reaches a very low level, the fungus can grow, clogging jets, sticking floats, and in sufficient quantities can make even the most battle hardened service techs cry like a little girl.

Here are some tips for cleaning a messy carb. First, wash any heavy dirt from the outside of the carb body, then remove and dismantle the carburetor. Make note of all component positions and fuel screw settings for proper reassembly. Be sure to write these settings down, and draw a simple diagram to help you remember the location of certain parts. You may find the older you get, the more valuable those diagrams become.

Next, soak all brass and aluminum parts in S-100™ (or Hondabrite™) cleaner. Although these products are made to clean off dirt and road grime, they work great to clean that nasty goo off carb parts (we discovered this trick quite by accident). Let the dirty parts soak for 2-3 hours in the cleaner at full strength. If residue still remains after soaking, carb cleaner can be used, but be careful not to get it on rubber parts, as carb cleaner causes most rubber parts to swell.

When the parts appear clean, rinse them off in solvent or contact cleaner, then blow dry them with compressed air. Next, reassemble the carburetor and adjust it according to your notes, or restore it to factory specifications if you need a reference point for tuning. Now you're ready to reinstall the carb back into your engine.

One way to keep from having to deal with clogged carburetors is to add fuel stabilizer to fresh fuel when filling up, especially if the machine is only used occasionally. Fuel quality isn't what it used to be, so it loses volatility a lot faster than it did years ago.

In addition, it helps to shut off the fuel valve and drain the float bowl if the machine is going to sit for 2 weeks or more as this makes for much easier starting next time.

Hopefully, these tips will help the next time you're faced with that "fungus among us."

Until next time, ride safe!

Have another topic suggestion in mind? Contact us to let us know!