Suzuki GSX-R750 Maintenance, Hub-Center Steering, Ignition Interruption Control

Answers

Ask The Pro
Q: I've been looking for a used Suzuki GSX-R750 for about two years now. While I've found a few examples that are cosmetically in very good shape, the owners of these bikes seem to believe in zero maintenance. Apparently these bikes are purchased, abused and sold every two years, buying a new one on credit and repeating the cycle. Most of the lack of maintenance is easily remedied, but my biggest concern is a lack of oil changes. I found a pristine 2006 model with 3400 miles for $6500, except it had never had an oil change. This is a really good price, but how much damage has been done without the initial 600-mile oil change? The owner hasn't let it warm up before taking off and revving it to redline, either. Should I walk away?
Mike Anzalone
Needham, MA

A: We dialed up GSX-R guru Carry Andrew at Hypercycle (www.hypercycle.com) in Van Nuys, California. Here's his take: "Before we address this, ask yourself how long you plan to keep it," Andrew says. "If the term 'forever' applies, walk away. If 20,000 to 35,000 miles is more realistic, I'd be willing to buy it. The oil-change issue really isn't, unless there is a burnt clutch involved. There just isn't enough foreign debris in the motor under normal use to worry about with that low mileage.

"The cold revving is a concern. It will eventually result in piston collapse from shrinkage at the piston skirt, and undue piston-ring wear. If the practice was infrequent, chances are such abuse had a minimal negative effect. Let the engine warm up (160-180 F) and hold it at 6000-7000 rpm for a few seconds and watch the exhaust. If you see blue or smelly smoke, walk away. Otherwise, the earlier logic applies."

Sound advice. There are too many solid GSX-Rs out there to get itchy about a shaky one. If in doubt, don't.

Got a question for answers? Send it to MCMAIL@sourceinterlink.com

Front and Center
You seem to have a very technical staff that does good techno-speak, but I'm often left longing for more depth. For example, the last paragraph of Alan Cathcart's "Future Perfect" column on page 19 of your January '08 issue. He states that, "Hub-center steering only works if everything else is in the right place," and then goes into tire wear and crashing implications. A few questions spring to mind: 1) What is hub-center steering? 2) How does it enable deeper braking? And 3) why does it destroy tires?

The answers may be self-evident to Sir Alan, but not to most readers.
Dave Molinari
Via e-mail

We put your query to our own James Parker, father of the RADD front end. Take it away, James...

"Hub-center steering is currently seen only on the Bimota Tesi/Vyrus. A hub-center front wheel has an axle that doesn't steer-just like a rear axle. But the inner part of the front wheel hub pivots on a pin through the axle, which forms the steering axis. That means the inner hub can be steered with a fixed axle, hence the hub-center designation. The inner hub is relatively large to make room for the steering pivot and provide useful steering angle. Bearings between the inner hub and the wheel are correspondingly large as well. Steering angle on these designs is very limited to keep bearing sizes reasonable. It's said that changing a Tesi front tire takes a dealer an hour and a half.

"Hub-center and other alternatives to the telescopic fork can enhance performance because they don't compress under braking, and thus retain suspension compliance. All the advanced front suspension systems allow harder braking as well. That means more force applied to the contact patch, which means more weight transfer, more heat and more tire wear. The right tire can deal with it, but one designed for a traditional telescopic fork might have problems. A tire that might work fine on a bike with a fork might be overworked with harder braking, so an alternatively suspended bike might need a harder compound or a different construction to cope."

Igneus Interruptus
In your first look at the Honda CBR1000RR, you mention that the ignition interrupt is for upshifting under power, like a quick-shifter. Other magazines, including your sister publication Sport Rider, say the ignition interrupt is for traction control. Which is it?
Travis Marshall
Via e-mail

Let us invoke the spirit of Soichiro Honda with a reading from the '08 CBR1000RR press kit: "In essence, Ignition Interruption Control uses sophisticated ignition mapping to reduce abrupt transitions and the shock forces generated as gearset and driveline lash is taken up at small throttle openings. Sensors compare engine speed to the speed of countershaft sprocket rotation and also factor in the degree of throttle opening. When engine speed surpasses countershaft speed by a predetermined threshold, Ignition Interruption Control interrupts some ignition pulses. In addition, the amount of interrupt is specifically programmed according to the gear selected-each of the six gearbox speeds has its own profile. This interruption allows a more gradual buildup of power, which reduces the shock forces that would otherwise be felt as a surge of driveline lash. However, all this begins and ends within milliseconds-the rider never consciously feels the brief interruption. Instead, it simply feels as though throttle applications occur with regular and remarkable smoothness." Translation? It's not traction control in any orthodox sense. More likely a way to smooth the segue from a closed to cracked throttle in the face of lean mixtures mandated by current squeaky-clean emissions regulations. Aaron Frank's First Ride reveals everything else about the maximum CBR elsewhere in this issue.

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