Why No Diesel Motorbikes ?

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Offline neilep

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Why No Diesel Motorbikes ?
« on: 02/12/2008 18:30:53 »
Hi All,

Iím Neil. Nice to meet ewe very much.

Do ewe like my bike ?

[attachment=5498]



..small eh ?..Unfortunately my neighbour parked his car in the wrong place. I literally had to go all out of my way to try and avoid not running over his car ten times !!

Now then,

Ewe have two types of engine yes ?  Petrol ?[attachment=5500]..diesel ?[attachment=5502]..theyíre the main two eh ?

How come ewe donít get diesel powered motorbikes ?..Iíve never seen one ..have ewe ?



Rev those thinking juices and let me know eh ?


Hugs & shmishes


Mwah mwah mwah mwah




Neil
Fat Bottomed Sheep
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Men are the same as women, just inside out !

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Offline graham.d

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Why No Diesel Motorbikes ?
« Reply #1 on: 02/12/2008 19:10:13 »
Good point Neil. I wonder whether it has to do with motorbikes having kick-starters. The high compression in a diesel would make it very hard to turn over by manual means. However many big bikes have electric starters now. Maybe it is just traditional.

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lyner

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Why No Diesel Motorbikes ?
« Reply #2 on: 02/12/2008 19:20:05 »
They also need a big flywheel. Could make them difficult to steer?
They wouldn't sound right either. . . .

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Offline ukmicky

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Why No Diesel Motorbikes ?
« Reply #3 on: 02/12/2008 19:48:12 »
You do get the odd deisel bike but a deisel engine is a lot heavier and expensive than a petrol one.

Petrol engines are also more responsive and better suited to the lighter bike.

Torque isnt everything and a bike does not require high torgue at low revs like a car. It requires an engine which delivers a good spread of power over a broader and much higher rev range than a deisel engine can deliver.

Deisel engine are better suited to heavy vehicles like cars or vehicles carrying a heavy loads as they produce a good low down spread of power.


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Offline Bored chemist

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Why No Diesel Motorbikes ?
« Reply #4 on: 02/12/2008 20:26:57 »
Presumably, much the same reasons explain why there are not many petrol trucks.
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Offline lightarrow

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Why No Diesel Motorbikes ?
« Reply #5 on: 02/12/2008 20:56:40 »
Presumably, much the same reasons explain why there are not many petrol trucks.
Yes, but also the fact that it would be more expensive (petrol engines have a lower efficiency) and maybe they also would be more dangerous in case of accident.
« Last Edit: 02/12/2008 20:58:36 by lightarrow »

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lyner

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Why No Diesel Motorbikes ?
« Reply #6 on: 02/12/2008 23:18:27 »
Quote
Torque isnt everything and a bike does not require high torgue at low revs like a car. It requires an engine which delivers a good spread of power over a broader and much higher rev range than a diesel engine can deliver.
That statement surprises me. I always heard that racing cycle engines were unbelievably 'peaky', had very light flywheels and needed a lot of gears to make up for it. Was that just true in the past?

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Offline Don_1

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Why No Diesel Motorbikes ?
« Reply #7 on: 03/12/2008 09:43:46 »
Petrol engines can be made fairly compact but diesel engines are necessarily large and heavy, they are also very noisy. Even the modern derv requires a good deal of sound insulation.
If brains were made of dynamite, I wouldn't have enough to blow my nose.

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Offline neilep

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Why No Diesel Motorbikes ?
« Reply #8 on: 03/12/2008 14:34:32 »
Good point Neil. I wonder whether it has to do with motorbikes having kick-starters. The high compression in a diesel would make it very hard to turn over by manual means. However many big bikes have electric starters now. Maybe it is just traditional.

Thanks Graham

Ewe may be right that it's down to tradition but I wonder if here is a mechanical reason behind it too. I notice there are other comments too so lets hope that below the answer is revealed !...(well...ABOVE this post  !!..oh...ewe know what I mean yes ?) [:D]
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Offline neilep

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Why No Diesel Motorbikes ?
« Reply #9 on: 03/12/2008 14:36:25 »
They also need a big flywheel. Could make them difficult to steer?
They wouldn't sound right either. . . .

Thank ewe Sophiecentaur. Yes I can see how a big flywheel would cause a slight issue when turning corner. Does the flywheel turn really really fast ?
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Offline neilep

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Why No Diesel Motorbikes ?
« Reply #10 on: 03/12/2008 14:39:40 »
You do get the odd deisel bike but a deisel engine is a lot heavier and expensive than a petrol one.

Petrol engines are also more responsive and better suited to the lighter bike.

Torque isnt everything and a bike does not require high torgue at low revs like a car. It requires an engine which delivers a good spread of power over a broader and much higher rev range than a deisel engine can deliver.

Deisel engine are better suited to heavy vehicles like cars or vehicles carrying a heavy loads as they produce a good low down spread of power.



Wicked !!  Thanks Michael...ewe know stuff !..ewe are klevur !

So really, it's a failing of diesel engine design then really !...they need to put their thinking caps on !!..honestly...what do we pay them for ?..just to sit there and produce bad designs !..hummpth !!
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Offline neilep

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Why No Diesel Motorbikes ?
« Reply #11 on: 03/12/2008 14:41:20 »
Petrol engines can be made fairly compact but diesel engines are necessarily large and heavy, they are also very noisy. Even the modern derv requires a good deal of sound insulation.

Thanks Don1, as i said above...they really need to get their act together and come up with a small diesel that does the job !
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Offline dentstudent

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Why No Diesel Motorbikes ?
« Reply #12 on: 03/12/2008 14:44:21 »
Petrol engines can be made fairly compact but diesel engines are necessarily large and heavy, they are also very noisy. Even the modern derv requires a good deal of sound insulation.

Thanks Don1, as i said above...they really need to get their act together and come up with a small diesel that does the job !

Why yes, yes they do!

[;)]

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Offline neilep

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Why No Diesel Motorbikes ?
« Reply #13 on: 03/12/2008 15:10:30 »
Petrol engines can be made fairly compact but diesel engines are necessarily large and heavy, they are also very noisy. Even the modern derv requires a good deal of sound insulation.

Thanks Don1, as i said above...they really need to get their act together and come up with a small diesel that does the job !

Why yes, yes they do!

[;)]

LOL !!   [;D]
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lyner

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Why No Diesel Motorbikes ?
« Reply #14 on: 03/12/2008 16:32:15 »
Model aircraft use a diesel cycle - no spark plug.

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Offline lightarrow

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Why No Diesel Motorbikes ?
« Reply #15 on: 04/12/2008 00:53:14 »
Model aircraft use a diesel cycle - no spark plug.
Are you sure it's a Diesel cicle? To have it you have to compress air and then inject the fuel in the chamber; I don't think this happens in model engines, I think it's more similar to a petrol engine and that the little candle, always hot, ignite the fuel/air (previously mixed) when the piston reaches ~ the right position, presumably because the fuel/air mix is more dense when it's compressed, or something like this.
« Last Edit: 04/12/2008 00:55:32 by lightarrow »

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Offline Ignorant Enthusiast

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Why No Diesel Motorbikes ?
« Reply #16 on: 04/12/2008 10:28:06 »
There are some diesel motorbikes, but no new commercially available ones. The US Army and MOD are looking at a diesel powered Kawasaki for future use (so that all their vehicles use the same fuel).

The main drawback for a diesel engined bike is that motorbikes are mainly luxury items now, so people want lightweight responsive bikes as play things as opposed to ones that do 150+ MPG as a means of transport.

newbielink:http://www.dieselbike.net/ [nonactive] has a lot of info on Diesel Bikes (the name kind of gives it away  [:)])

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Offline LeeE

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Why No Diesel Motorbikes ?
« Reply #17 on: 05/12/2008 00:59:25 »
Re the model aircraft engines: I believe that you can get both spark-plug and glow-plug engines.  The glow-plug engines rely upon the glow-plug remaining hot throughout the cycle of the engine and not only does the glow-plug initiate the burn but it does so in a controlled way - the burn starts from a known point in the cylinder instead of just happening anywhere.  The shockwave from the burn has to be predictable and constant, otherwise you'd get wide variations in stresses and power on each stroke.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline lightarrow

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Why No Diesel Motorbikes ?
« Reply #18 on: 05/12/2008 18:26:17 »
Re the model aircraft engines: I believe that you can get both spark-plug and glow-plug engines.  The glow-plug engines rely upon the glow-plug remaining hot throughout the cycle of the engine and not only does the glow-plug initiate the burn but it does so in a controlled way - the burn starts from a known point in the cylinder instead of just happening anywhere.  The shockwave from the burn has to be predictable and constant, otherwise you'd get wide variations in stresses and power on each stroke.
I wonder how the glow-plug starts the combustion at the right moment.

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lyner

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Why No Diesel Motorbikes ?
« Reply #19 on: 05/12/2008 19:07:36 »
Re the model aircraft engines: I believe that you can get both spark-plug and glow-plug engines.  The glow-plug engines rely upon the glow-plug remaining hot throughout the cycle of the engine and not only does the glow-plug initiate the burn but it does so in a controlled way - the burn  starts from a known point in the cylinder instead of just happening anywhere.  The shockwave from the burn has to be predictable and constant, otherwise you'd get wide variations in stresses and power on each stroke.
I wonder how the glow-plug starts the combustion at the right moment.

Anyone who has tried to start a 'naff' model aircraft engine will know that it is very critical.

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Offline LeeE

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Why No Diesel Motorbikes ?
« Reply #20 on: 06/12/2008 05:46:45 »
Quote
I wonder how the glow-plug starts the combustion at the right moment.

http://en.wikipedia.org/wiki/Glow_plug_(model_engine)
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline neilep

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« Reply #21 on: 08/12/2008 18:39:02 »
There are some diesel motorbikes, but no new commercially available ones. The US Army and MOD are looking at a diesel powered Kawasaki for future use (so that all their vehicles use the same fuel).

The main drawback for a diesel engined bike is that motorbikes are mainly luxury items now, so people want lightweight responsive bikes as play things as opposed to ones that do 150+ MPG as a means of transport.

http://www.dieselbike.net/ has a lot of info on Diesel Bikes (the name kind of gives it away  [:)])

Thank ewe Ignorant Enthusiast I appreciate your answer and your link.
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Offline Bored chemist

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« Reply #22 on: 08/12/2008 19:22:09 »
Just for the record, there are real diesel (i.e. compression ignition) engines used in model aircraft. No spark plug or glow plug.
"Diesel engines are another choice but are the least common of all IC model aero engines.

Diesel model airplane engines, such as the PAW shown right, are typically used in vintage rc airplanes to keep the model as authentic as possible; such engines were being manufactured long before glow plug technology, and so were the first IC engines to be used in radio control flying.

Diesel engines do not use any form of plug for ignition, but instead rely on the fuel/air mixture inside the combustion chamber to ignite from the friction heat generated by the piston moving up and down as the prop is flicked over to start.
The pressure inside the chamber can be increased or decreased by turning a threaded screw on top of the cylinder head; increasing pressure aids ignition of the fuel/air mixture. The fuel is a special mix that has a high ether content, which is easily ignited"

from here
http://www.rc-airplane-world.com/model-airplane-engines.html
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Offline LeeE

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Why No Diesel Motorbikes ?
« Reply #23 on: 10/12/2008 00:12:27 »
Ta for that BC - didn't know about them.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline moonrider

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Why No Diesel Motorbikes ?
« Reply #24 on: 02/06/2009 10:57:47 »
Well, now I see what makes it hard for some or should I say almost of the motorbikes to be diesel-operated and not those usual engine oils that we use. The comments in this post made me think of such things. I almost overlook at them because I just got used to it. I think a site that i have visited may be able to clarify things in here maybe you'll be interested in looking more through things.
« Last Edit: 03/04/2012 17:14:32 by peppercorn »

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Offline nicephotog

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Why No Diesel Motorbikes ?
« Reply #25 on: 04/06/2009 12:20:28 »
The correct terminology of a diesel engine is a "compression ignition engine".
Bikes do not have suitable space and places by design constraint to put:
A. Injector rack
B.fuel filter (required to be checked)
C. A deliberate fuel pump

These three last points are massively critical requirements to operate a diesel engine with any reliability and efficiency for an economic market. So therefore are almost redundant for design purpose and impossible economically to include.

--added edited--

Another factor in design less seldom know is the safety requirement legislation for market in each country. Because of mounting more exposed both critical and complex parts the equipment of a motorcycle would require greater investment in safety technology and engineering, so hence the R&D costs to successfully make these extra parts safe under the enormously dangerous conditions of a motorcycles' operation is too much.

another factor is the control(use) of acceleration in the revolution band and burning speed of the fuels(diesel) energy yield is not the same as with petrol and again hence requires a different set of gear ratios in the gearbox not parts that can be interchanged or match that of the petrol for production cost.

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Offline moonrider

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« Reply #26 on: 12/06/2009 03:39:11 »
The defining feature of the diesel engine is the use of the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol (gasoline) engine or gas engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.
« Last Edit: 03/04/2012 17:14:06 by peppercorn »