random trivia.
The SVS hit 1500 miles today. I'm sure I'm the only one who cares about that, and I barely do. ;)

please don't sue me.
The first three of today's pictures were shamelessly stolen from Pete Shoemark's Motorcycle Basics Manual. The last two were shamelessly stolen from the May 2001 issue of Friction Zone. I'll bet if you go and buy copies of their products, they won't be as pissed at me for ganking their stuff. Hint hint.

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Blantant disregard for the law aside, I really like riding with Kim. Even the couple of miles home from Noelani's house last night was fun. I like riding with any of my friends, but it's extra-neat to ride with Kim; it's like I look up and my brain goes, "Hey, look! That's Kim up there on that bike! Look how cute Kim is! Zoom!" and it makes me happy. It's like when I'm riding with Peter and he's wearing his little leather jacket and I get all funny and think "Wow, there's this cute guy on a motorcycle in leather, and I'm going home with him! Mrow!" only probably a little bit different.

I'm sorry, that was my outside voice again, wasn't it?

more than we wanted to know, there.
So, speaking of Kim being a bad influence, we were meeting at a local strip mall yesterday morning to have lunch. A few minutes before I was about to leave, Kim calls and says, "oh, I got here early so I'm just going to run down to Bike World." Bike World is the Kawasaki/Suzuki dealer, which is right next door to the restaurant. Naturally, I met her at Bike World, and we gooed over the pretties. Since it was Kim's fault we met there, I'll try to pretend it was Kim's fault that I went inside the dealer and bought a Mag-Knight magnetic tank pad (I bought the one on the left). It fits on the tank like this, but less ugly, since the one I bought is smaller. So, hopefully, I'll prevent further scratches on the tank from my jacket buttons (there's one there now). I haven't put it on yet, because for some reason they tell you to heat it up with a hair dryer first, and god knows I don't care enough about my hair to own a hair dryer. So I'll bring it to Peter's this weekend, where I can temporarily pilfer his roommate's girlfriend's hair care products.

more mechanic stuff.
So, Peter called the dealer today and ordered a bunch of parts (new sparkplugs, new clutch plates, etc), which now guarantees that we'll find other stuff that needs to be replaced. I think he's getting a little sick of driving his car in the gorgeous weather lately (though, for heaven's sake, he has a copy of my Nighthawk key), which, hey, is cool with me. I want him out riding with me, too. :) So, it looks like we'll be tearing the bike apart more tomorrow; maybe we'll get the valve adjustment done or something. I've been reading through his Joy That Is Clymers, so hopefully both of us have a vague idea of what the hell we're doing this time, and it won't take forever.

While I was at Bike World yesterday, I picked up a copy of the May issue of Friction Zone. Free bike magazines == good. This month's "Engines 101" article was about the drive train, which was very cool and very bad. It was very cool because I realized that I don't really get how the drive train works, and it forced me to think about it and understand it a little. It was very bad because it made me realize that I don't really get how the drive train works, and now my obsessive-compulsive brain wants to rip open the Nighthawk again so I can get a "hands-on" idea of what's going on (Peter, I see you wincing over there. Stop that. I wouldn't until we were done with your bike). So I contented myself with spending the last hour pouring over my various mechanical references and both the SVS and Nighthawk owner's manuals. I am proud to say that I can now say with some authority that no one on the planet can explain drive trains well. I'll now join those ranks.

the drive train according to poof.
OK, so there are four parts to the drive train: the clutch, the transmission, the crankshaft, and the final drive. The crankshaft is turned by the engine; when the tach says your bike is idling at 1500rpms, say, it means that the crankshaft is rotating at 1500 revolutions per minute. The crankshaft ends in a gear. This gear sits right next to the gear on the outside of the clutch assembly. When the clutch is engaged (while riding), the two gears mesh together: the engine turns the crankshaft, and therefore the crankshaft gear; the crankshaft gear turns the clutch assembly. This is where things start getting cool.

I'm going to segue to the clutch for just a second. The clutch assembly is made up of two parts: the outer housing, and the inner hub. The housing is also sometimes called a "basket" or "drum," and the hub is sometimes referred to as the "core." At any rate, there are two types of clutch plates: the plain plates, and the friction plates. Without getting into too much detail here (I'll cover the clutch some other time), suffice it to say that the plain plates always rotate with the inner hub, and the friction plates always rotate with the outer housing. OK, back to to the drive train.

To tie both of those sections together, let's revisit the last part of the first paragraph. When the clutch is engaged, the crankshaft gear meshes with the outer clutch housing, and turns it. Now, as we just learned, this will also turn all of the friction plates. Everyone with me? Good, because this is where it gets neat. When the clutch is engaged, a pressure plate with a spring pushes against the clutch plates, forcing them all together. The friction plates, which are lined with cork, "catch" on the plain plates, forcing them to turn as well. Basically, there's no gears or anything involved there, it's just pressure turning those plain plates. Now, as we learned, the plain plates are attached to the clutch hub, so, not terribly surprisingly, when the plain plates are rotating, so is the clutch hub. When the clutch is disengaged (squeezed in), however, the outer housing is still rotated by the crankshaft, but the pressure plate moves away from the clutch plates and doesn't put any pressure on them. Therefore, the friction plates continue to spin (since they move with the housing), but the plain plates and, therefore, the hub, remain motionless.

The clutch hub, in turn, is physically attached to a shaft called the mainshaft (just to be confusing, in the above picture, it's labelled the "input shaft"). Therefore, it follows that when the engine is running and the clutch is engaged, this mainshaft is turning (everyone see why? The engine spins the crankshaft, and when the clutch is engaged, the crankshaft spins the entire clutch assembly as one, and since the inner hub of the clutch is connected to the mainshaft, the latter spins as well). OK. Here's where it gets sort of tricky. Bear with me. The mainshaft has an assortment of gears around it; some are physically attached to the mainshaft, and others spin freely. A second shaft, called the layshaft or countershaft, sits parallel to the mainshaft. It, too, has an assortment of splined (attached) and freewheeling gears on it. At all times, there is at least one gear on the mainshaft which is meshed with a gear on the countershaft; this means that the countershaft turns only when the mainshaft is turning (and when is that? Right, when the engine is running and the clutch is engaged). This means -- and this is important -- that when the clutch is disengaged (squeezed in), the coutershaft does not spin. Remember that.

OK, everyone still with me? We're almost done. Remember all those gears on the mainshaft and the countershaft? Well, to make matters even more complicated, those gears that are splined onto the shafts can move horizontally along those splines. Why would they want to do that? Well, all of those gears on both shafts are of various sizes. When you want your bike to go faster, you upshift, right? You do that because you want a smaller gear ratio between the mainshaft and the countershaft. I bet you didn't even know that that's what you wanted! Look how smart you are. The reason that you want a smaller gear ratio is simple. We'll go back to the general concept for a second, and the zoom back in on this detail. The countershaft has one very important role: it has a sprocket on the end of it which should be familiar to you. It's the sprocket that controls the final drive, which in most cases, will be a chain. If you look at your bike chain, find the front sprocket that the chain fits around; that's the sprocket on the end of the countershaft. So, you see, the countershaft is responsible for turning the rear wheel of the motorcycle! How fast the rear wheel turns (and therefore, how fast the bike moves) is directly proportional to the revolutions per minute (rpm) of the countershaft.

So, let's get back to the gearing on the mainshaft and countershaft. This part is hard for me to explain, so hopefully it'll make sense. If a small gear on the mainshaft meshes with a large gear on the countershaft, then the mainshaft gear will rotate more per minute than the countershaft gear. Let's say that the mainshaft gear rotates twice for each single rotation of the crankshaft gear (giving it a gear ratio of 2). Higher gear ratios provide more torque (because the rotating gear is physically larger), so lower gears (first gear, second gear, etc) have higher gear ratios than upper gears. This is because it takes quite a bit of torque to get a heavy motorcycle going from a stop -- try starting from a stop when you're in 6th gear and see how well it works (hint: it doesn't). A gear ratio of 2 is just about first gear; fifth gear has a gear ratio of closer to .9. So, what's the point? The point is that different gears (first gear, second gear, etc) on a motorcycle need different gear ratios. This means that depending on which gear you're in when you're tearing down the freeway, the mainshaft gears have to be meshed with different countershaft gears, in order to mesh the two together that'll have the right gear ratio.

Whew! OK. so, in order to do that, we need to be able to slide the splined gears horizontally so that they'll match up with the right gear on the other shaft. This is done with a part called a shifter fork. A five gear bike will have three: one to control fourth gear, one for first and second gears, and one for third (yes, that seems as arbitrary to me as it does you.). One end of a shifter fork is connected to a sliding splined gear on one of the shafts. The other end is mounted on an axle inside a box called the shifter cam. OK, so now we know that a shifter fork moves a sliding gear, but what moves the shifter fork? Simple. The end of the fork that's inside the shifter cam has a little pin sticking out of it. The pin rests in a groove on a big cylindar called the shifter cam assembly (which also sits in the shifter cam, not surprisingly). The grooves aren't straight around the shifter cam assembly; they have kinks and bends in them. The picture below will clarify this. Anyway, the shifter cam assembly is physically connected to the shift lever. When you press down (or lift up) on the shift lever with your boot, it rotates the shifter cam assembly. This causes the pin to move along the groove, and if the groove kinks, the pin will end up in a different spot horizontally than it started out in. Since the pin is attached to the shifter fork, and the shifter fork is attached to the sliding splined gear on the shaft, you can hopefully see how the gear gets moved horizontally along the shaft.

Sooo...in summary, you've gotten all your gear on, you've turned the bike on, and you're sitting on it all ready to go. You squeeze in the clutch. Here's what's happening:

• When the engine is running and the clutch is disengaged (squeezed in), the engine turns the crankshaft, which spins the clutch outer housing. However, since the plates aren't pressed together, the inner hub doesn't turn, and therefore neither does the mainshaft. If the mainshaft isn't spinning, neither is the countershaft, and therefore neither is the sprocket for the chain. The rear wheel doesn't turn; your bike stays still.
• You stomp down on the shift lever to put the bike into first gear. The shifter cam assembly rotates, causing the shifter forks to follow the groove in the assembly. The forks push the sliding splined gears on the mainshaft and countershaft together in the appropriate manner to get the correct gear ratio for first gear.
• When you start to let out the clutch, through the friction zone, to start the bike moving, the crankshaft and clutch outer housing are still spinning. This time, though, the pressure plate in the clutch starts to press the plates together, causing the plain plates -- and therefore the inner hub -- to spin. The inner hub is connected to the mainshaft, so it's spinning now, too. The mainshaft gears are now lined up with the correct countershaft gears (thanks to the shifter forks), so the mainshaft starts the countershaft spinning. The countershaft sprocket on the end of the shaft begins turning the chain, which runs to the rear sprocket, and the wheel begins to move.

Whew. I hope you feel smarter now. :)