Don't take the ****, I'm only asking...

[essexplumber]

Why are there no diesel motorbikes/mopeds etc?

[anonymous-user]

There are. Mainly from the military and usa.

[kambites]

Traditionally, diesel engines have always had a very poor power to weight ratio.

[thinfourth2]

There are

Royal Enfield made one

There isn't any main stream ones

[essexplumber]

kambites said:

Traditionally, diesel engines have always had a very poor power to weight ratio.

That would make sense. I imagine a diesel bike would go forever on a tank of said fuel wouldn't it?

[Hugo a Gogo]

Royal Enfield made one in India

they were crap, but got 200mpg

[kambites]

essexplumber said:

kambites said:

Traditionally, diesel engines have always had a very poor power to weight ratio.

That would make sense. I imagine a diesel bike would go forever on a tank of said fuel wouldn't it?

I suppose so, but it seems that range has never been of much concern for bike manufacturers. I suppose because most of them don't get used for high mileages.

If a manufacturer really wanted to, I think they could get well into three figures for mpg for a petrol bike. The market just doesn't seem to care.

Edited by kambites on Tuesday 19th October 18:32

[SystemParanoia]

http://www.dieselbike.net/yanmar/yanmar.htm

[Dr Derek Doctors]

I may be talking rubbish here but a few years ago a reasonably high up army type told me that the British army were aiming to have diesel motorbikes at some point in the future so that logistically they only had to deal with one type of fuel.

[essexplumber]

So in answer to my question there are loads of diesel bikes. What factors would make a diesel bike unfavourable when compared to a petrol?

[Hugo a Gogo]

that's exactly what the US army are trying to do (and everyone else in NATO in believe)
have all vehicles able to run on jet fuel basically

[SystemParanoia]

Hugo a Gogo said:

that's exactly what the US army are trying to do (and everyone else in NATO in believe)
have all vehicles able to run on jet fuel basically

sorted

[Mastodon2]

essexplumber said:

So in answer to my question there are loads of diesel bikes. What factors would make a diesel bike unfavourable when compared to a petrol?

Slow burning fuel requiring high compression, making them slow to rev and giving them a low redline. Hardly good for hooning and thunderously quick acceleration.

[swamp]

There is a modified Kawasaki diesel bike:

http://www.motorbikestoday.com/features/Articles/d...

I believe NATO are standardised on diesel across the board. No good having army motorbikes if you can't fill them with fuel!

[kambites]

essexplumber said:

So in answer to my question there are loads of diesel bikes. What factors would make a diesel bike unfavourable when compared to a petrol?

I think the real question is why would anyone bother? The characteristics that make turbo-diesels so good for daily drivers in cars are not what you want in a bike. Too much low down torque would be completely wasted on something weighing 200kg and no-one really seems to care about fuel economy or cruising range on a bike.

On the other hand they tend to be heavy; to get any kind of power from a physically small engine you need a bloody great big turbo which is a nightmare to package on a bike and would need to be very carefully insulated since they get so hot. They're a nightmare to start because they're so high compression so you need a (relatively) big battery and starter motor which add yet more weight and bulk to the whole system.

Edited by kambites on Tuesday 19th October 19:02

[Hugo a Gogo]

SystemParanoia said:

Hugo a Gogo said:

that's exactly what the US army are trying to do (and everyone else in NATO in believe)
have all vehicles able to run on jet fuel basically

sorted

that one can run on Diesel!

[maser_spyder]

Mastodon2 said:

essexplumber said:

So in answer to my question there are loads of diesel bikes. What factors would make a diesel bike unfavourable when compared to a petrol?

Slow burning fuel requiring high compression, making them slow to rev and giving them a low redline. Hardly good for hooning and thunderously quick acceleration.

But surely you've just described a Harley?

[crofty1984]

kambites said:

If a manufacturer really wanted to, I think they could get well into three figures for mpg for a petrol bike. The market just doesn't seem to care.

Edited by kambites on Tuesday 19th October 18:32

Honda CG125 ridden gently must crack that sureley?

[kambites]

crofty1984] said:

Honda CG125 ridden gently must crack that sureley?

I think there are bikes that will do 100mpg, but then there are cars that get close to that and you only have to look at the power to top speed ratio of sports bikes to see that bikes have a lot less drag, despite the rubbish Cd. I think a usable, 300-400mpg petrol bike ought to be perfectly achievable if there was a market for it.

[Chris993C4]

Dr Derek Doctors said:

I may be talking rubbish here but a few years ago a reasonably high up army type told me that the British army were aiming to have diesel motorbikes at some point in the future so that logistically they only had to deal with one type of fuel.

Sounds entirely plausible - NATO Common Fuel Policy dictated that British Army Landy 90/100s were diesel, whereas the previous Series IIIs were invariably petrol...