timing belts?

[aspeyrer]

so why does a ducati have a timing belt? why not a timing chain? chains would last longer and prevent engine damage when the timing belt breaks, which can and has happened. chains might make the valve train maintenace less frequent.
i have a 2003 suzuki sv 1000, its a v-twin, and makes as much Hp as a ducati 998, and it has a timing chain. the valve only need service every 15,000miles. costs half of what a used 998 would cost. just seems like the more expensive motorcycle in this comparison cost more to maintain, which normal thinking should be the other way around. the more expensive, be better built motorcycle should be less maintenace intensive.
i agree the 998 looks better, i have always wanted a 748, 916, 996, or 998.
but the high maintenace schedule and the nearest ducati dealer is 5 hrs away.
just my 2 cents

[YellowDuck]

With the desmo valve actuation (no valve springs) there is very little resistance in the valve train and so very little force required to turn the cams. Thus, you can use a belt where a chain would normally be required. As for any actual advantage of the belt vs a chain, I will leave that to others - not sure. Maybe less mass = less inertia = more power under acceleration?

But anyway, the shorter maintenance interval is not a function of the belt vs the chain so much as it is the need to keep the valve clearances (openers and closers) in spec on the desmo. Since the valve movement is under positive actuation from a cam in both directions, you sure don't want the clearances to get so tight that the two cams are fighting one another, nor so loose that the valve gets thrown a long distance between contact with the opener and closer surfaces as it changes directions.

But I am no engineer, so maybe all of the above is hooey!

[twowheelcossack]

I think that any chain stretch would be the death knell for our favorite valve-actuation system or would at least throw the adjustment hopelessly out of whack. Belts don't allow stretch or necessitate the need for a high-force tensioner system.

[Desmo_Demon]

I kinda like the idea of bouncing the engine off of the rev limiter and not having to worry about valve float.......and having a piston smack a valve that didn't close fast enough.

[flyinlow1]

Belts DO stretch just like a chain can stretch, thats why there are belt tension devices on the motor. On belt drive bikes as with chain drive bikes, you have to check and adjust tension, with the exception of the Buell, which has an automatic tension adjuster.

My old 1990 Mitsubishi Eclipse had a belt driving the overhead cams and it had an automatic tensioner on it. These automatic tension devices are really nothing more than spring loaded pulleys.

As to why use a belt instead of a chain? Cheaper, less mass and weight and with the maintenance schedule of the valves, the belt tension can be adjusted at the same time anyway.

[jethro911]

Honda V4 gear driven cams cannot be beat! Zero maintenance and nice whirring sound. BTDT for many years, they just need a chassis IMHO.

[aspeyrer]

Originally Posted by flyinlow1

Belts DO stretch just like a chain can stretch, thats why there are belt tension devices on the motor. On belt drive bikes as with chain drive bikes, you have to check and adjust tension, with the exception of the Buell, which has an automatic tension adjuster.

My old 1990 Mitsubishi Eclipse had a belt driving the overhead cams and it had an automatic tensioner on it. These automatic tension devices are really nothing more than spring loaded pulleys.

As to why use a belt instead of a chain? Cheaper, less mass and weight and with the maintenance schedule of the valves, the belt tension can be adjusted at the same time anyway.

yeah maintenance schedule that would be 15,000miles for my sv1000
your ducati will need to be adjusted at least3 maybe 4 times at about 400 dollars each time, you do the math. or should i say ducati needs to do the math.
i really like the ducati 748,916,996,and 998 just don't like there mentality on there bikes. for the price you pay for a ducati, the maintenance should be a lot less intensive.

[B_Cebrian]

I wouldn't race a 998 rider for pinks if I were you. The cost of the bike is not just in the engine. Suspension, brakes, chasse all are vastly superior on the 998. The belt is for the lightness of the system. The lack of resistance in the desmo valve system. Modern kevlar: belts for all purposes do not stretch. When they fail, they break. Yes you have to manually adjust the tension, but many racers replace their I-4 auto chain tensoners with manual ones due to the likely failure of the auto adjuster under race condition. In fact The biggest problem with the original Honda F-4 was chain tensioner failures. Great bike with a small problem that was quickly fixed. The frequency of the valve check intervals has to do with the requirement to maintain very strick valve clearances with the desmo system. You don't have to be as ridgid with a conventional spring/valve system. Yes Ducatis are expensive to own and maintain. Not so much if you do your own work, but expensive if you have it done. If you're not a good hand with a wrench then stay away unless your bank account can cover it. If you like your Zuk, keep it, nice bikes. I own one and it's okay. I prefer Ducati. It has nothin to do with the cost. Though I sure wouldn't turn down a GSXR-750 track bike if someone wanted to give one to me.

[OldBaldy]

Originally Posted by aspeyrer

yeah maintenance schedule that would be 15,000miles for my sv1000
your ducati will need to be adjusted at least3 maybe 4 times at about 400 dollars each time, you do the math. or should i say ducati needs to do the math.
i really like the ducati 748,916,996,and 998 just don't like there mentality on there bikes. for the price you pay for a ducati, the maintenance should be a lot less intensive.

Belts are no more service intensive than chains, really - I mean - virtually ANYONE with enough brain to breathe can easily and quickly check and adjust/replace a belt every 2 years or so. There are no crank chain pulleys to wear out, requiring a new crank is some cases!, no adjuster blades to wear out, no issues with tensioner plungers backing out on high RPM overrun, etc, etc, etc. - and they are quieter and much more fun to watch when left exposed and see the cam pulleys and belts whirring around...

Besides - they're different!

And don't even THINK about comparing the work to adjust a Duc's valves to a Honda Interceptor! Just how many times do you have to remove and reinstall the cams on THAT thing?

[Buckelew]

I had a TL1000S when they first came out in 1997; the valve adjustments were simple, easy, and quick. Having that intermediate timing gear that drove the cam made things real simple.

Still.....the ride of the Ducati....made it all worthwhile.