Service
SERVICE
Hub-center steering mystery
How does a bike with hub-center steering steer sharply to the right? I can understand left turns, but it seems to me than in right turns, the rear of the tire would bang into the swingarm.
Please illuminate me on this matter. I've not seen one of these vehicles in real life, so maybe I'm missing something....
Rev. J. H. Spielberger, Jr. Bunker Hill, Illinois
We'll assume you `re referring specifically to the ELF X, and its unusual front suspension with swingarms only on the left side of the front wheel. And the answer is that the ELF X doesn `t turn sharply to the right or the left. Race bikes usually don `t have much steering lock: only 20 degrees in either direction is required by the regulations, and the ELF X can turn its wheel that far without contact ing its swingarms. At racing speeds and during racing conditions, that's more than enough. But try to turn around in a narrow driveway with 20 degrees of lock, and you `11 be wishing for more. Street versions of motorcycles with suspensions like that on the ELF X will have to offer more steering lock if they are to be truly streetworthy.
More on warped rotors
Several months ago you ran a letter in your service column from D.J. Minor of Champlin, Minnesota, who was experiencing warped front brake rotors on a 1982 GS1 100EZ. Your advice to him, since his rotors had already been replaced three times, was to have the warped rotors machined true, because the warpage had been caused by stresses left in the rotors during manufacturing that were relieved by the heat generated by braking.
I, too, have a GS1 100EZ, and after 4000 miles I experienced warped front brake rotors that my dealer agreed to replace under war ranty. When I asked the service manager if it wouldn't be cheaper and more permanent to machine them as you suggested instead of replacing the rotors, he replied that the rotors can't be machined be cause they have a hardened coating. Grinding would remove the coating and drastic wear would result.
I was very pleased with the prompt warranty service, but I feel certain this problem will reoccur with the new rotors. Who's right? Do I have my rotors machined next time as a permanent fix, or will I be replacing brake rotors every few thousand miles? If I do have the rotors turned down will I need new brake pads to mate properly?
M.J. Lester Manville, New Jersey
There is no hard coaling on the stainless rotors that would be removed by grinding, so machining the rotors is an~option. It's quite possible, however, that your rotor warpage problems won `t reoccur, and we'd recommend a wait-and-see attitude; don `Ifix some thing that isn `t broken.
iJyour rotors do require machining, we'd suggest using new brake pads with the fresh rotor surfaces for the most even pad contact, but that isn `t essential.
Chassis design information
I am a member of a group of mechanical engineering students at the University of Central Florida. We are currently engaged in design ing a new front suspension for motorcycles as an alternative to the venerable but dated telescopic fork.
This is our senior design project, and though we do have several cre ative design ideas, we lack some of the technical information to design this system adequately. Any information you can give us on the basics of suspension geometry or fur ther sources you could direct us to would be appreciated.
Lee M. Potter Cocoa Beach, Florida
The best sources on suspension geo~netry and chassis design would be: Motorcycle Chassis Design: the the ory and practice, by Thny Foale and Vic Willoughby, published by Osprey, London; and Motorcycle Dynamics and Rider Control, published by the Society of A utomotive Engineers. Both books are available from Classic Motorbooks, P.O. Box 1, Osceola, WI 54020.
Triple fireworks tips
I'm writing in response to the Feb ruary, 1985, service letter entitled "Two-stroke fireworks." I'm a senior mechanical engineering student at the university of Iowa and I'm cur rently building a two-stroke rocket myself. I chose a 1973 Kawasaki 750 H2 and modified it with expansion chambers, 35mm Mikuni car buretors, a Barnett clutch, ported cylinders and milled heads.
I would recommend Bill Wirges for any Kawasaki Triple cylinder and head work. Wirges has set FIM speed records with Kawasaki Triple engines, and he's a virtual encyclopedia of how to trick-out Tri ples. He also makes expansion chambers and swingarms for the Kawasakis. His address is Wirges Creative Performance, RR#2, Princeton, Illinois 61356.
As far as lightweight parts like plastic tanks or clip-ons are con cerned, try Racer's Supply at 6959 Van Nuys Boulevard, Van Nuys, CA 91405.
Kelly Coffield Pleasant Valley, Iowa
