10 THINGS YOU NEED TO KNOW ABOUT CLUTCH & THROTTLE CABLES

(1) Components. Dirt bike control cables consist of an external housing and an inner wire that slides through it. The wire transfers force to and from the controls on the bars to components of the engine (throttle, hot-start, clutch or compression release). The housing has a threaded length adjuster and end caps (called ferrules) at the ends. Each end of the wire has a soldered-on fitting, which is usually a barrel type on dirt bikes. Some applications utilize an aluminum elbow to hold the cable at a strict bend for routing purposes.

(2) Housing. The housing consists of a semi-rigid, metallic skeleton with a vinyl inner liner and outer coating. The metallic skeleton can be constructed in different ways. A coil-wound cable means that the skeleton’s metallic strands spiral around the housing like a coil spring. A coil-wound cable is more willing to make curves and bends, but the housing is more likely to compress and bind. A longitudinally wound cable means that the structure runs straight (lengthwise) down the cable. Longitudinally wound cables aren’t as pliable, but are less prone to binding. Manufacturers take the routing of specific applications into account. As a rule, the modern four-strokes’ compact features cause more routing bends than the old two-strokes.

(3) Inner layer. The vinyl inner layer must be hard for durability and offer low-friction capabilities for the inner wire to slide on. If the liner is too hard, however, the housing won’t bend easily. Worse yet, it will transmit perceptible vibration to the control lever. The vinyl liner has natural lubrication to help the wire slide. All cables have similar vinyl (PVC) material with slight variations in hardness. The outer layer of the cable housing is sometimes coated or wrapped in a steel braid on street cruisers, but this is only cosmetic.

(4) Inner control wire. The inner control wire is made with separate steel (usually stainless steel) strands that are tightly woven together. There are different thicknesses and different coarseness of the material and weave, but the resulting wire is always very strong. The design does have one drawback: the weave makes the wire into a serrated saw blade. Eventually, the inner control wire will saw through the nylon liner and cause metal-to-metal contact with the housing structure.

(5) Wear. If any visible portion of the inner control wire is frayed, it can cause the throttle or clutch to stick. It must be replaced. Wear on the inner nylon liner isn’t visually observable, so it’s a judgment call based on feel. Although you could purchase all the individual components of a cable and build one yourself, it’s a much better idea to simply replace the entire unit with a professionally built, certified cable. If one part of the cable is worn, the other parts probably aren’t far behind anyway.

(6) Installation. Some factories grease their cables, but most new cables are sold dry—without lubricant. It’s important to lube a new cable before use. When routing a new cable, it is best to keep it as straight as possible. Bends in the cable create drag. The best strategy is to route the new cable along the same path as the old cable. The exposed inner
control wire at the ends of a cable is the most likely part to get damaged. Be gentle when assembling the throttle tube/housing and the clutch lever/perch. Make sure rubber covers are in place to block debris. Tune in the desired free-play (just a bit of wiggle) with the in-line adjusters. Double-check the cable routing by turning the bars from stop to stop. Make certain that there is still the same amount of free-play at each stop and that the cable can’t get pinched or kinked.

(7) Maintenance. Lubing cables is a commonly neglected task, but it’s important. Over time, dirt and water contaminate cables. The best method for lubing a cable is to use a purpose-built cable luber. It clamps to the end of the housing of a cable and force-feeds lube into the housing. You can also use the cable luber to flush the contaminated lube and grit with light lubricating oil. WD40 is great for reducing friction in a cable, but it coagulates and attracts dirt. A purpose-built cable lubricant is best. Motion Pro’s T-3 cables have a lubing port built right into their housings.

(8) Adjuster. Cables don’t stretch. If you have to readjust free-play, it is due to heat expansion or wear someplace else. On the clutch cable, it is possible to have three different adjusters: one in-line adjuster near each end of the cable and one built into the perch. Modern four-stokes have two throttle cables that push and pull simultaneously. From a design standpoint, it is not necessary to have two throttle cables, but this is where lawyers are more important than engineers.

(9) Cable failure. Cable failure can cause the loss of control of a vehicle, thus all cables must meet international standards for durability and strength. Cables are tested above 30,000 pounds of force and run through thousands of actuation cycles.

(10) Cable vs. hydraulic. Hydraulic systems naturally adjust and compensate for heat expansion, which can be really handy. Although hydraulic brake controls are much more accurate than cable controls, a cable-actuated clutch does allow for more precise control than a hydraulic one. With the direct mechanical connection of a cable, the clutch can be finessed more accurately. A hydraulic clutch saves the clutch plates and compensates for abuse but is more vague. Plus, cables don’t leak.

2013 BIKES! FIRST LOOK AT THE 2013 KTM 50SX, 65SX, 85SX, 125/150SX, 250SX, 350SXF & 450SXF

2013 KTM 125/150SX
Benefiting mostly from the plastic, chassis and running gear changes (shared among every model), the 125SX and 150SX do not get any engine mods for 2013.


2013 KTM 250SX
The 2013 two-strokes get U.S. spec suspension settings, including the shorter shock lengths for the first time. Additionally, the 250SX get stiffer fork springs, DDS (Damped Diaphragm Steel) clutch, Moto Tassinari VForce4 reed block and all-orange plastic. The two-strokes do not get the stiffer head tube reinforcing or thinner frame cradle tubes that the four-strokes get (because they don’t need them).
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All the 2013 bikes will get the larger 25mm rear axle (accessed by a 32mm nut) and the beefed-up one-piece cast swingarm.  The spokes are anodized black.

The 250SX two-stroke will get the diaphragm clutch from the 450SXF. It uses a single Belleville washer-style spring, steel basket and is 5.5mm narrower than the previous coil spring clutch. Plus, it gets a new clutch cover.

Visible in this photo is the new thread-on gas cap, which uses very unique internal threads, the redesigned triple clamps, taller Renthal 827 Fat Bars and two-tone grips.

The KTM two-strokes get KTM’s almost bulletproof nylon silencer hanger system. All of the KTM’s, two-and four-stroke, are two-meter-max legal.

2013 KTM 250SXF
The new engine is the big news, but the 2013 KTM 250SXF also has a six-speed tranny that operates via a steel basket, coil spring, hydraulic clutch. The counter balancer shares the same shaft as the water pump and timing chain to save weight. The engine will not accept optional kickstarting (as it did last year). The 250SXF and 350SXF get new head pipes, plus tapered mid-pipes and muffler cores.


The KTM 250SXF engine is built on all-new engine cases and gets its inspiration from the KTM 350SXF engine. The exhaust system gets a resonance chamber (as does the 350SXF). All of the KTM’s are two-meter-max legal. All the 2013 frames are painted gun metal gray.  The 2013 KTM 250SXF shares very little with last year’s engine. The DOHC, titanium-valved, finger follower engine has larger port areas, 1.6mm larger intake valves (now 32.5mm), bridged-boxed piston, 2mm bigger bore and 2.5mm shorter stroke. The 250SXF rev limiter is set at 13,400 rpm. The horsepower is claimed to be five more ponies than last year.

Graced with billet hubs, Excel rims and a powerful 260mm Brembo front brake, the KTM’s dominate the braking categories.

2013 KTM 350SXF
Every 2013 KTM will have the gun metal gray frame, all-orange plastic, I-beam front fender and Renthal 827 bars. The four-strokes also get gussetted head tubes (via an X-brace inside the head tube gussetting), thinner wall frame cradles and lighter linkage bolts. The 350SXF engine gets a new cylinder head, enlarged water jacket, Pankl rod, resonance chamber and high-tech die-cast cases. The EFI throttle body has been enlarged from 42mm to 44mm.


The bodywork is derived from the “Ryan Dungey Replica.” The air box is new.

2013 KTM 450SXF
Based on the “Factory Edition” model used by Ryan Dungey, the 2013 450SXF is fuel injected (with a 44mm throttle body), has a different bore and stroke than last year (95mm x 63.4mm compared to 97mm x 60.8mm), a Konig bridge-boxed piston, Pankl rod and crank, and plain bearing on the big-end. The 450SXF does not have the resonance chamber that it had last year. All of the 2013 KTM four-strokes get additional and improved fuel filters – inline, at the fuel pump and at the injector body.


The KTM 450SXF gets firmer damping front and rear, especially in the midstroke compared to previous models. The spring rate front and rear remains the same, as does the rising rate linkage.

2013 KTM 85SX

2013 KTM 65SX

2013 KTM 50SX

2013 Troy Lee Designs GP AIR MIRAGE

2013 Troy Lee Designs GP AIR TEAM

Justin Shantie from JDR/J-Star KTM shows us how to properly install a holeshot device on Matt Moss’s KTM 250SX-F.

Source: Motocross Action Mag

10 THINGS YOU NEED TO KNOW ABOUT INNER TUBES

(1) Inner tubes are a mix of natural and synthetic rubber. Natural rubber is more pliable and offers better resistance to punctures, but synthetic rubber is cheaper. Expensive racing tubes generally have a higher percentage of natural rubber to better form to the tire and to prevent flats. There are also solid foam inserts (called mousse tubes) that simulate air pressure from a foam tube.

(2) For a motorcycle manufacturer, the inner tubes are an easy place to save weight and money. Most bikes come stock with thinner and cheaper tubes. Since the entire mass of an inner tube is rotating mass and unsprung weight, it is a prime place to save weight. Conversely, almost every factory racer runs heavy-duty tubes (or mousses) to prevent flats.

(3) Having the proper size inner tube for the tire is important for performance and preventing pinches. If you install a 110 inner tube in a 100 tire, the excess rubber will render it susceptible to being pinched with the tire irons. An inner tube that is too small for a given tire will have to be overinflated to make up the difference in size. Overinflation weakens the ability of the inner tube to resist damage. It is possible to run a smaller tube to save weight, but it isn’t recommended.

(4) Inner tubes play a large role in the feel and performance of the tire. Inner tubes must be the correct shape and size to sit flush against the sidewall to give a good, consistent feel. If there are places where the inner tube isn’t in contact, the tire will feel mushy.

(5) Inflating an inner tube to the proper pressure not only ensures more sidewall strength, but also prevents pinch flats. As a rule of thumb, 12 to 14 pounds per square inch (psi) is the standard recommended pressure. Keep in mind that as the tire heats up during operation, internal pressures can increase by as much as four psi. This can be lessened by using nitrogen in the tubes to avoid the water content and heat expansion.

(6) Inner tubes are available in a variety of thicknesses to provide the appropriate amount of protection against flats. A thin inner tube is approximately 1.5mm to 1.75mm thick. A heavy-duty tube is around 2mm to 3mm thick. And a super-heavy-duty tube is 3.5mm to 5mm thick. The weight of a thin 110-90-19 inner tube is about 1230 grams (2.71 pounds), while a 3.5mm super-heavy-duty 110-90-19 weighs 1720 grams (3.79 pounds). For comparison purposes, a mousse tube tips the scales at 1950 grams (4.29 pounds).

(7) If an inner tube isn’t installed properly, it can fail. Using corn starch or baby powder on the inner tube during installation will reduce friction between the inner tube and the tire’s carcass to help the tube last longer. Adding a little air to shape the inner tube before mounting the tire can help prevent pinches during tire installation.

(8) The valve stem is the weak point of a tube. It is vulnerable to damage and leaks. The valve stem is vulcanized to the tube and can be torn off if the tire spins on the rim, so be sure the rim lock is properly installed. Never tighten the nut on the valve stem down to the rim. If you leave it loose, the tire can spin a little without ripping the valve stem off the tire. You can tell when the tire has spun on the rim because the valve stem will be cocked at an angle. Make sure to re-center the valve stem any time you see it angled.

(9) An inner tube is made to handle the abuse of a tire carcass, but not the outside elements. If water or dirt gets between the tire and tube, it will grate against the inner tube. Be sure that contaminants can’t get in through the rim lock or valve stem holes. The rubber grommet that comes stock on Hondas is a good idea. Replacing the standard rubber rim strip with duct tape makes it more difficult for water to get past the spoke nipples.

(10) Even if your inner tube hasn’t gone flat, it can wear out. Dunlop recommends changing tubes every six months. To know when to replace a tube, look for chaffing, strings of rubber, discoloring (an old tube gets darker) or fading of any writing on the tube. Amazingly, patched tubes will work as well as a new tube, but the patch is a weak point and ideally should only be used in a pinch (pun intended).