Why don't Harley Davidson offer a driveshaft?

Because the engine is in the wrong way, it involves either a complex joint or rotating the engine – exactly like Moto Guzzi have been doing for decades.

Which reveals a problem, the torque makes for an interesting experience as the shaft revolves.

Belt drives are more efficient at transferring power than drive shafts are. Belt drives transfer something like 92% of power to the rear wheel whereas driveshafts can lose up to 31% of power! That s not good when you consider the fact that Harleys generally have less than 200 hp and lb/ft of torque. Imagine only having 100 bhp and but only 69 hp at the rear wheel. That would pretty much suck!

Also, The added unsprung mass of a driveshaft system on a motorcycle can have some interesting handling effects.

Maintenance on a belt drive isn t horrible nor does it need to happen frequently.

Belt drives are a LOT less expensive.

Truth is, Harleys don t make enough power to justify a drive shaft. Don t hate on me for saying so though. I have no desire to ride anything but a cruiser and Harleys are my favorite make.

Because belt drive is their 'thing'. Belts are quiet and very reliable and require no regular maintenance. They do require occasional replacement, but Harley knows their market well. Most Harley riders don't ride more than a couple thousand miles a year. They will never come up to a belt replacement.

Yes, driveshafts do let go in cars. It's fairly rare, but there are a lot of cars out there. BMW has had a lot of problems with it's final drive systems on its motorcycles. They keep trying new things and getting it wrong. So far, the K1600 system seems to be holding up.....

Belts and driveshafts are limiting if you want to change final gearing. chains and sprockets make that easy.

Ninebad is unable to say anything positive about a HD, and about cruisers in general. Funny how the US cruiser bike market outsells all other bike styles combined.

Both my bikes have driveshafts. They are heavy, more expensive to build, transmit power less effeciently and altering final drive ratios is next to impossible. They are dependable and clean, but when one goes bad, there's a good possibility you will end up in the ditch with your a$$ in the air. Just ask anyone who ever owned a Suzuki Cavalvade what happens.

Belts are lighter, cleaner than a chain, transmit power more effeciently than a shaft, less expensive to build, ratios can be changed and are as dependable as shafts. The 5 HD guys I ride with have all had belt drive bikes and have ridden all over the US and Canada for over 20 years without a belt failure. One guy had a sharp rock cut the belt, but even then it never failed. And lets not forget that Kawasaki used a belt on the KZ440 back in the 80's and there are other non-HDs that use belts.

I like this question , There is a way to put a drive shaft on a Harley without turning the motor. You have a cased spider gear comming off the main drive shaft off the transmission , this however would entail a lot of engineering and unless they want to spend the time on R&D I doubt it will happen, cost factor is also a concern. HD already has a over priced motorcycle on any level , either entry level sportster to the cruisers , in my opinion only. Still customized bike ratios is always an aspect the consumer likes to spend their money on. Would be interesting to see though.

Rich

Shafts aren't the perfect solution either. They have their own inherent problems, and they aren't exactly maintenance free. I have had 3 belt-drive Harleys and a Buell. I never had a problem at all with any of them. For a moderately powered motorcycle they have all the benefits of a chain drive without the drawbacks, and they have a longer service life. It's actually a pretty good system.

I think its part of the HD image. My M109R has a drive shaft and there are pros and cons. A con is that you get some vibration when your RPM's come up because the drive shaft isnt properly balanced. However, Ill never have to oil a chain or worry about a chain or belt breaking. Also, drive shafts are more money and Im sure this is a big factor for HD.

Drive Shaft Bike

Many motorcycles have used shaft drive in the past, but with improved modern technology, the belt drive systems that are currently in use for Harleys and other big twins are actually more efficient and they save weight too.

Not sure of the reason , But drive shafts can and do fail, I think HD just keeps it traditional or maybe its the cost factor