Friday, June 10, 2005

Ninjas and the Art of Motorcycle Maintenance

Back in 1998, I got a new job on the northwest side of Altanta (near the Cobb Galleria), and needed a commuter vehicle to make the trip back and forth from Athens. My selection was a new 1997 Kawasaki Ninja ZX-6, a 600 cc, 98-hp crotch rocket. The first month of this was an interesting odyssey, since it was January, and even in Georgia, it can get cold (near-freezing). In addition to this, the first 500 mi is the break-in period, which required keeping the engine below 4000 rpm. On the highway, this equated to about 52 mph. This made for a fairly long and unpleasant commute, since the temperatures were in the low- to mid-thirties (F), and the traffic on GA-316 and I-85 is posted for 65 mph but goes 75 mph, and the traffic on I-285 is posted for 55 mph but goes 85 mph. Fortunately, since the trip was 150 miles/day, I didn't have to do this too long, and was not run over.

First maintenance comes, and amounts to nearly $400. You see, on a sportbike like the Ninja, where the engine redlines at 14K rpm, the DOHC valvetrain cannot afford the luxury of hydraulic lifters, and it tends to need regular clearance checking and adjustment. The checking consists of tearing off most of the bodywork, the fuel tank, the air cleaner, the carburetors, the ignition coils, the spark plugs, and finally the valve cover, and then measuring the clearance with feeler gauges. If you are unfortunate enough to require adjustment, then the camshafts must be removed, along with the valve lifter, and then a tiny shim under the lifter must be replaced with another tiny shim that's thicker or thinner. As you might guess, this is somewhat labor-intensive, and comes around every three- to six-thousand miles.

But at least after the first maintenance, I am able to take the engine to 6000 rpm, which is about 70 mph, for the next 500 miles. These 500 miles go past quickly, and at that point, you are completely done with the break-in, and the sky's the limit.

The Kawasaki power curve corresponds roughly with the Spaceballs speed nomeclature:

  • 2000-4000 rpm: Light Speed
  • 4000-7000 rpm: Ridiculous Speed
  • 7000-10,000 rpm: Ludicrous Speed
  • 10,000-? rpm: Plaid
Still, any commute that takes you through Spaghetti Junction on a friday night is not fun. Once this asshole in a riced-up Acura wanted to race me at night at GA-316. I was cruising along at a lesuirely 75 mph and wasn't really interested. He finally went around me, and then he flipped a cigarette butt out the window, which goes into his slipstream and is carried up and literally hits me right between the eyes. (Yes, I wear a full-face helmet.) So I drop down two gears, which puts me squarely in the Ludicrous Speed band, pass him like he was standing still, and then find a mini-van up head, and then slow down and sit in the left lane so that he's stuck behind us.

Another time, during daylight hours, I was going more-or-less the speed limit, when it suddenly begins to rain. Hard. Raindrops, especially large raindrops, sting pretty good at that speed. There are hardly any overpasses on 316 to duck under, so rather than stop and get soaked, I pushed up to a speed where the bow shock of the bike pushed the raindrops around me.

Fortunately, after a couple of months, I got to work from home for the most part, which saved me a lot of time and money. After a year or so, I actually got an office in Athens through an acquisition, which was great, since working from home can make you a little crazy after awhile. One day I was going in to work on the north side of the Athens perimeter and exiting on Chase St. The exit's since been redone a little bit to widen it but at the time it was one lane, and it actually drops off quite a bit, so it's hard to see what's on the ramp until you're on it. On this occassion, there was a pickup truck, which I saw first, and then saw it was towing one of those low garden trailers, the kind you use to haul around lawn tractors. I know I locked up the rear brake, and then I got on the front really hard, so hard it threw me off, and I dumped the bike. Fortunately I did not hit the trailer, and I did not break any bones. Unfortunately I broke the left foot peg mounting bracket, so I couldn't shift, and I had to ride to work (and later home) in 5th gear.

The bike sat for a long while, in part because I had to figure out what parts I needed to order. Finding the food peg bracket was hard. You'd think it would be listed under "frame", but it was with "battery box". During this time, the carbs gummed up a bit, and it didn't idle well, and sometimes didn't want to crank. One morning last summer, not long after replacing the original tires, I tried to start it and something broke: The starter would turn, but the engine would not. So I ended up parking it for the season, again.

This summer (in fact, in the last two weeks), I started tearing into it, with the expectation of replacing the starter. I've replaced starters on cars before, and this is nothing like a car starter. On a car starter, there is a solenoid that pushes out the gear to engage with the flywheel/starter gear, and then retracts once the car is started. On the ZX-6, there's just a shaft with teeth. This engages with a reduction gear, which in turn engages a large gear on the end of the crank. This gear is actually free-spinning on the crank, except that it is mated to the alternator rotor via a one-way clutch. So when you engage the starter, this turns the big gear, which causes the alterator rotor to turn, which causes the crank to turn; and when you disengage the starter, the big gear doesn't turn, relative to the crankcase, though the crankshaft is spinning inside of it.

The problem was: The alternator rotor is fixed onto position on the crank via a Woodruff key and a keyway, and the key had been sheared off. There's also a big bolt that holds the rotor on, and that was being unscrewed as I tried to start the engine, so it's a really good thing I never tried to push-start the bike, since that would have probably done a lot of damage to at least the alternator.

I had pretty much resigned myself to repairing or replacing the crankshaft (big job), but I called Falicon Crankshaft Components and was told I could probably remove the old key with a punch and press in another one. Now I just need to find a punch and the right size key and I should be good to go.


  • Sportbikes are not good long-range commuter vehicles.
  • Don't neglect your fuel system. The crank failure was due to hard starting, which was likely due to gummed-up carburetors leaking gas into the cylinder. (Dropping the bike on the alternator cover probably didn't help either.)
  • You don't own a Ninja; the Ninja owns you.

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