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Gold Member/Community Dad
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Discussion Starter #1
Harley's have been using Belt drives for years. And Buell and it's spread to a few others. I really don't know but it seems like it's a good system - works, new belt every 25k miles?, clean, auto-tension, efficient. Why aren't the 4 Japanese companies trying this out on the Sport/Standard bikes? Any thoughts?

Berto
 

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Good question.. I've been wondering that as well. Maybe it has to do with the HP. Harley's have little compared to the rest of the world (45 hp on an 800 cc bike, 60 -70 on a 1200??). Any takers on this one?

kelly
 

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Wheelie for Safety
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One problem I have read with the belt drive is that small rocks can get trapped between the belt and pulley. Then the belt gets quickly destroyed. I guess it doesn't matter with a Harley because a ride wouldn't be complete without a major break down.
 

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another problem is drive lash. the belt stretches a bit when undr tension (accelerating) and that gives a slight delay between throttle application and acceleration. not a big deal on cruisers, far from ideal on sport bikes. the new firebolt uses a special pulley that keeps the belt pre-tensioned to help eliminate this.

they're also significantly wider. not a major problem but it is something to ba accounted for when designing.

but i agree, the minimal maintenance is appealing. my last bike had shaft drive and it was nice not to have to lube the chain.

scott :)
 

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Belt drives are easier to maintain and quieter. I'm not real sure, but I think Kelly is probably real close to the truth of the matter (hp). While not a real high hp motor, H-D's still have alot of torque. It may also have something to do with the sizes of the sprockets and cog drives. The entire case would have to be redesigned and be recast. As for rocks eating belts, yeah it's a possibility, but I haven't heard of any instances. My sister and her husband are both hard core, "dyed in the wool" H-D folks and neither of them of had the problem or heard of it taking place. The belts they run have some "Kevlar" construction of some type and my bro-in-law says they are pretty tough and will run as long and sometimes longer than a chain.

Shaft? Wasn't he in a movie? :laugh:
 

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But remember.... the Harley's have a totally separate engine and transmission which are connected with a two-row chain. It's really a different animal, so I don't pretend to know the answer to this question. Perhaps somebody with a Harley connection could delve (sp?) into this.

Kelly
 

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BMW's F650 has been released in road only form with a belt drive. It's really designed at enticing non-motorcyclists into the fold so a belt was considered cleaner and quieter than a chain.




:)
 

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Discussion Starter #10
Martin,

I'll bet the retooling/redesign is a major undertaking and the Japanese may see it as a risk - don't won't to fall away competitively while they perfect it. Shaft! Yeah, the man, two movies - he didn't look the same in the second one! Still... very cool though.

Kelly,

Buell is using belts on their 500-1200cc bikes so wouldn't think HP/Torque is a big issue. I saw that new belt tensioner on the Firebolt at the Bike show - it looked liked it would work fine.

Tom,

Shaft (not the movie) drives are quite a bit less efficient (power transfer) than a chain/belt. The feel is akin to the first time I had a front wheel drive car and put it in reverse. Car drops down. The shaft drives tend to feel tighter, especially downshifting, lock up that rear wheel briefly til the revs come down. Not as sporting a nature - but their getting better. Think BMW may be up a step or two in this area.

Berto
 

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Hello everyone,

Here is my input:

1. The belts have improved a lot the last years. 10 years ago the belt would have to be HUGE to take 100HP.
Actually the problem is torque and not HP. The V-Rod uses a belt and has a little more than 100 HP and has a lot of torque (75lb/ft at 7500 I think).
2. It's true that the belt will be destroyed very fast if the bike is taken slightly off-road and debris is trapped between Belt-pulley.
3. Even the new Kevlar belts etc. can't take the power of a real sportbike. The belt would be so wide that it would be the first part to touch down when turning!!! A British mag took 4 sportbikes to south Europe for testing. There was a Buell in them, but the belt broke on the second day of abuse. This means something....
4. Shafts consume more power than chains/belts, and also create reactions while accelerating/deccelerating as the torque plays with the suspension. Paralever by BMW and other systems handle this nowadays. My 1976 R75/6 goes up and down nicely when you play with the throttle, not so good in the bends :(
The only plus is they don't need maintenance, except changing the oil every now and then.

I hope this info clears things a bit.

Aris
 

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Discussion Starter #12
good info

Aris,

I thought Buell was racing in Supersport (last season may have been last) or another class. Wonder if they converted to a chain to uh.... stay on the track with the rest of them.

Berto
 
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