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Discussion Starter #1
Sprockets:

When you change the gear ratio on your EX500 you can change the front or the rear or both of the sprockets. Lets say you want to gear your bike down lower, then you can put on a smaller front or larger rear sprocket. Changing the front sprocket will change the force acting on the drive chain. If you go with a smaller front then the force on the chain will increase because the force on the chain is the torque at the drive sprocket divided by the radius of that sprocket. The smaller the diameter of the sprocket, the higher the force on the drive chain. If you go to a 15 tooth from a 16 tooth you’ve increased the gear ratio by about 6.5% and increased the force on the drive chain by about 6.5% and you’ve shorted the life of the chain since it now has a greater force pulling on it. Also, you’ll need to lube the chain more often since each link will be bending more over the smaller sprocket, increasing the maintenance you have to do.

Now lets say you increase the size of the rear sprocket from a 45 tooth to a 48 tooth instead of making the front sprocket smaller. You still have about a 6.5% change in the gear ratio and since you haven’t changed the size of the drive sprocket you haven’t changed the force on the chain and it will last just as long as it used to. Since the rear sprocket is larger it will weigh more and the chain will be going faster as it goes around the sprocket. Since the extra weight is rotating weight it requires extra force to get it to rotate and will slow down your acceleration a small amount and will increase your breaking distance. The decrease in acceleration and increase in breaking distance will be so small you’ll never notice them. Since the sprocket is larger and the drive chain is going faster as it goes around it, it will throw off more lube than it used to and you’ll need to lube the drive chain more often than before the change to keep it oiled. You’ll probably need a longer chain with the larger rear sprocket which will also add weight.

Your choice is a smaller front sprocket and increased drive chain wear or a larger rear sprocket and increase rotating weight. For a street bike I recommend the larger rear sprocket since the loss in performance is neglectable whereas the loss in drive chain life due to using a smaller front sprocket is a nuisance. For a race bike I might go with the smaller front sprocket since replacing the chain more often isn’t really a factor and keeping the rotating weight to a minimum is important.

If you want to gear you bike up then I’d say go with a larger front sprocket (if it will fit) because that will reduce the force and wear on the drive chain making it last longer. But if a larger front sprocket wont fit, then just go with a smaller rear sprocket. I personally think the stock gearing is perfect for normal street use on my 2006 Ninja 500R.

The choice is yours. I think that belt drive is the right way to go, but the Japanese haven’t caught up to Harley-Davidson yet.
 

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they put belt drives on the vulcans. doesn't a belt drive make the bike wider due to the cog width vs sprockets?i had a vulcan 500 years ago with belt drive and it was low maintenance and quiet too
 

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Discussion Starter #3
The width of the belt is determined by the diameter of the drive pulley. The larger the diameter of the drive pulley the less force is transmitted to the belt and the thiner the belt can be to handle that force. Belt drive pulleys are larger diameter than chain drive sprockets so that less force is put into the belt but it all depends on how the engine was designed as to whether you can get a large enough pulley in there. If I were designing a new engine to use belt drive I would design it to have enough room for a large diameter pulley and a thiner belt. And if you have to use a wider belt, it's still only the belt drive that's wider, the engine stays the same width except at the output. Yes the swingarm will have to be a little bit wider but that doesn't really affect how the bike works. The handlebars aren't any wider, the gas tank isn't wider, the seat isn't wider, etc, etc, etc. Having a little bit wider swingarm seems to me to be a small price to pay for the much lower maintainace that you get from a belt drive.
 

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But then on the other hand, a 14 tooth front sprocket is about $16 shipped to your door. A larger rear sprocket is more like $40. Rear sprocket requires wheel removal. Front sprocket takes just a few minutes.

Personally, I'm running a stock rear sprocket and a 14 tooth front sprocket, and my bike is a wheelie monster. It's still quite comfortable at 80mph on the highway, though. Stock, the EX is geared WAY too high. The engine runs out of power before it runs out of gear. Most I could get with a stock setup was near 120, not even redlined in 5th. Bike wouldn't accellerate at all in 6th. Top speed is about the same now, but I hit it in 6th, and I have a lot more fun getting there.

Charles.
 

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But back on the first hand ;) it's generally a good idea to swap sprockets in sets anyway (on a street bike at least). So you're laying down the money for sprockets regardless of how many teeth on the front or rear.
 
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