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Feb 2010 Vol 10 - No 2 - The Valve Stem by Alex Ford PDF Print E-mail
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Thursday, 04 March 2010 19:19
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Feb 2010 Vol 10 - No 2
Group Riding Formations- Cluster or Solo? By Ben Harper
The Valve Stem by Alex Ford
Fuel Pump Gravity Feed by Dave Wolf
Rear Brake Switch by Dave Wolf
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 The Valve Stem by Alex Ford

Kyle Bradshaw over at Cruiser Customizing just regaled me with an interesting video on changing one's oil and he actually used the V-Star 1300, proving that the bike caught the attention of the Aftermarket people. And, it's a Star. Not to mention a V-Same.

Those people changing a flat or putting new rubber on their V-Stars probably know something about their valve stems, but those who let the dealer handle all of the changes might be surprised to know that there are several different types of valve stems and that more than one type has gone on to V-Stars since the 1990's intro of the cruiser from Yamaha Star Motorcycles.

For the spoke wheel editions, the valve stem is part of the tube, unless the owner has had his rims made into the tubeless variety. Sometimes when that is performed at considerable expense, the selection of the valve stem and type, and in some cases, modification of the hole size in the rim to accommodate the valve stem and type must be made.

The Cast Wheel Edition V-Stars have stock R & D which includes a larger and fatter hole on the front and narrower stock wheel, than the rear fatter and smaller wheel on the rear. Let's say that again: Front wheels, 16” on the Cast Wheel editions, have a larger hole in the rim. The 15" Rear wheel has a much smaller hole in the rim. Reason: The front cast wheel uses am all rubber valve which is pressed into the rim. The air is maintained well by sealing the hole at its edge and on both the inner and outer surfaces of the rim material. Thus, when changing a wheel or tire an air pressure check should be done on that all-rubber valve seal to ensure that air continues to be maintained with no leaks. The valve stem cannot be rebuilt. The metal portion of the valve has been surrounded by the vulcanization process used in making the valve. Still, it is possible to use in its place what is known as a "solid valve stem. This is a steel valve stem that fills the same hole, without modification of the hole in the rim. The solid stem can be "rebuilt." That is, the stem can accommodate not only the grommet that surrounds it when new, but the grommet can be removed from the stem and replaced with a new rubber grommet when changing the tire for any reason or time. While the rubber unit was pressed into the rim, the solid variety is place through the hole with its rubber grommet, often of a two-shelf or shouldered variety rubber grommet, and is held tight to one surface of the rim with a screw-type jam retention and a second jam nut so that the desired torque is maintain. This allows a single surface grommet to be used. "Solid Valves," of this type allow for customization of the valve stem angle and include direct 45-degree angle stems; perpendicular+45 degree angle stems and Perpendicular+90 degree angle stems. These have value on wheels with dual disc brake set ups where the rotors make it nearly impossible to get an air gauge in to check the air pressure of the wheel and tire combination. The solid valve stems also provide show bikes with all chrome sections of rims to maintain a chrome appearance, because the solid portion or core of the valve stem can be sent in for chroming or polishing and show chroming. No small point to certain bike owners.

The 15 inch cast rear wheel from Star, remember has the smaller hole in the rim for the valve stem, despite the fact that it is a fatter wheel and smaller in circumference than the front unit. The V-Stars 650 and 1100's have a shaft final drive instead of a belt. The result is that there is a disc brake side and a drive side which create clearly more access space on one side only of the motorcycle, when it comes to putting air in the tires. For that reason, Star chose to place a solid-type valve stem in the rear wheel. The stem comes out initially perpendicular to the rim surface and after several millimeters of climb away from the center, a 90-degree angle (bent like mandrel bending so there is no buckling at the elbow joint) is developed in the valve stem. This is installed so that the valve stem exits with its access hole facing away from the rotor and perpendicular to the bike itself. Thus the cyclist has only to place the rubber air in a straight 180-degree line with the stem, allowing filling of the tire to the desired air pressure without having to bend the air hose. Further, the valve can be removed and polished and chromed at any point. New washers with the appropriate shoulder or use of the original washer that has been carefully slipped off of the stem can then be accomplished. The retention is a feature of two jam nuts which also may be chromed. These can normally be steel or stainless steel as is the 90-degree bent valve-stem-unit. Torque on the stem must be sufficient to maintain an air-tight seal of only one surface of the rim, but not too tight which could damage the rubber stem parts. The unit itself has a much smaller diameter hole in the stem and the end of the stem has a metal shoulder against which the rubber grommet with shoulder is applied.

This concludes the Star Cast Wheel Edition Valve Stems 101 article. It is hoped that this will stimulate some discussion or that valve stem experts will weigh in on this area of motorcycle maintenance and mechanics with even more information than is normally discussed regarding the valve stems of tires and wheels.

Last Updated on Friday, 05 March 2010 12:54
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