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Discussion Starter #1
Why don't the moderate power sport bikes like the 500r and the new 636 come with belt drives rather than chains? Seems like it would be less maintenance and the belts appear to be quite reliable. A number of manufacturers are now using them, including Kawisaki in the new vulcan 900.
 

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I read some horror stories about belt problems on mybuell.com but the guys I know with Buells sure have not had any problems, at least with the belts. And I don't think that power is the limitation on their use since some big torquey equipment use belts for power transmission.

My main fear would be getting solid debris dragged in by the belt and locking things up or breaking the belt but I suppose that could happen with a chain too.

Maybe too manufacturers just don't want to spend marketing $$ on convincing customers that belts are OK for sportbikes. The cruiser guys have already bought into it.
 

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i have ridden both belt and chain driven and ill take a chain any day. belts being made of rubber have an elasticity feel on the takeoff and application of power that i just dont particularly care for.
 

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i use to have a vulcan, i kinda liked the belt drive due to ease of maintenance. to have one on a ex would make the bike a lot wider.
 

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Discussion Starter #5
Thanks for the quick replies. I still think the new 636 would be the "perfect" medium sized sportbike if it only had belt drive, but sounds like it's a personal preference issue. By the way, why would it be a lot wider with a belt drive? Are the belts that much wider than chains?
 

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ummm.... the "NEW" 636 is actually 599... they did away with the 636cc engine in favor of the homologated 599cc power plant.
and yes, belts are quite a bit wider than chains... by a lot.

how well do belts perform when under extremely high speeds anyway?
 
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Only belt driven bike I've ridden is my dad's '83 Honda Custom 250. Between the vibrations when it tries to reach it max speed of 110km per hour and the laggy take off (feels like it's pulling a trailer), I couldn't even think to 'feel' what the belt was doing :)
 

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I prefer my chain drive anyday. belt drive isnt a SPORT bike thing, its a cruiser thing IMO. chains are better for sportbikes because they give an instant reaction and are generally what I've always known. belts may be lighter, and equally strong, but just dont belong on a TRUE sportbike. and no I dont care for buells, they're ugly hunks of crap to me.
 

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I've ridden a lot of Buells and they have zero drive line lash unlike a chain does. This is because the belt is tight where a chain needs slack.

How thick the belt needs to be depends on how much power is at the rear wheel. In the past belt technology wasn't up to speed with sport bikes but since Buell starting using them they have become much better. The new belts never need to be replaced unless damaged.

I suspect the reason a belt isn't on the 500 is because most people prefer chains. Chains do offer qucker gearing changes for track days.

So, there's no real reason why a 500 couldn't have a belt.
 

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The answer is simple power/strenght belts have more friction than chains so you loose power and it would take a pretty wide belt to have the same strenght as a modern 520 or 530 chain.
 

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OK, this is the truth about the strength of a chain or a belt needed by a motorcycle. It's determined by the torque output from the transmission AND THE DIAMETER OF THE DRIVE PULLY OR SPROCKET coming out of the transmission. For an EX500 the engine torque is about 35 ft lbs. The primary gear and the first gear ratio in the transmission are 2.652 and 2.571. So, the torque out of the transmission is equal to 2.652 x 2.571 x 35 = 239 ft lbs. The diameter of the 16 tooth sprocket is about 3" (I haven't measured one but 3" is close) or 1/4 of a foot. So the force on the chain at peak torque in first gear would be about 956 lbs (239 ft lbs / 1/4 ft). If you wanted to run a belt you could put a 6" pulley on the transmission output instead of the 3" sprocket and reduce the force to 478 lbs, which can easily be handled by a narrow belt. Of course, you'd also need a 16" diameter rear wheel pulley to replace the current 8" diameter gear to keep the overall gear ratio the same.

So you don't need a wide belt to match the strength of the chain, you just need a larger diameter pulley to lower the force on the belt and then use a thin belt.

I don't know how much power is lost to a belt or a chain drive. You could test this on a Harley, run it on a dyno with the belt drive, change to a chain drive and run it on the dyno again. But I haven't seen this info ever published by a motorcycle magazine. I guess they just don't care about telling us the truth.

The problem with reducing the force on the final drive belt/chain is that current engines aren't designed for a large diameter sprocket/pulley. This would mean a redesign of the EX500 engines, which is probably cost prohibitive.

As far as making your bike wider, well your handlebars are about 26" wide and I don't think they'll become 32" wide with a belt drive. I don't think the 16" wide gas tank will be any wider either. Only the mufflers would have to be redesigned in order to not be wider by an inch or two (they are currently about 26" wide) if a wide belt drive where put on the EX500. If a narrow belt drive is used you wouldn't even notice the extra width of the mufflers.
 

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A dramatic increase in sprocket diameter will effect the leverage over the rear suspension as it moves the force way above the swingarm C/L. I suspect it would cause a problem with excessive squat on accelleration but never tried it.

And belts are GREAT with high speed. It's chains that actually have trouble with speed in part because it's hard to keep lube in them. With the advent of sealed "O" rings this has been satisfactorily resolved.
 

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Discussion Starter #13
Hotrod, that was a great response, and it all sounds like it's correct. I'm not mechanically smart enough to know whether it is ( all correct ), but until someone convinces me otherwise I think I'm in agreement with you on belts/chains. Thanks.
 

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To ninjamom,
Thanks. I hope it was all correct. At this age I tend to forget things sometimes.

To dad,
If you build your new, 2008 EX500 with a large pulley belt drive and you just copy the way the transmission output shaft and swingarm were made 20 years ago, yes, you'd increase the squat on acceleration. But if you use your head and redesign the bike you'd put the swingarm pivot above the transmission output shaft's center line so that the torque reaction wouldn't be so great.



In the middle drawing, the torque reaction would be higher with the larger diameter pulleys but the torque of the little 500cc engine isn't going to be very much anyway. In the bottom drawing, the swingarm pivot has been raised to reduce the torque reaction. You can either raise the swingarm pivot point or lower the output shaft of the transmission, both will work the same.

Of course, we'd have to see what difference this makes when decelerating (you wouldn't want your bike to project you out of your seat and over the handlebars when you let up on the gas ;D) but I suspect that a 500cc engine doesn't make that much of a difference and is safe no mater what you design.
 

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