Test ride : Honda CB1000R. 2021 model.

[Mr. Dazzle]

These PB thrust curves could show that as they charted the rear wheel thrust in each gear vs speed, they looked like this, often with the drag curve combined to show the theoretical top speed

I remember those....I thought I'd imagined it, cause whenever I've looked in bike mags recently (not that often TBF) they didn't have them. ISTR it was standard practice in the oft repeated 600 shootout etc.

If I may beat the same old drum again: EVs will change all this. They'll give you maximum thrust across a huge speed range with no need to change gear.

[weeksy]

If I may beat the same old drum again: EVs will change all this. They'll give you maximum thrust across a huge speed range with no need to change gear.

LOL none of us will want or buy one.

[Mr. Dazzle]

If I may beat the same old drum again: EVs will change all this. They'll give you maximum thrust across a huge speed range with no need to change gear.

LOL none of us will want or buy one.

You probably didn't think you wanted a big naked Honda either...

[The Spin Doctor]

I have been thinking about this lately and was reminded that back in the 80’s, 90’s when John Robinson wrote for PB he would often chart the thrust curves for bikes on test.
The thrust curve is a product of the combination of the power, revs, gearing that most closely represents the ‘feel’ of a bikes drive system.

Thrust curves are by far and away the most useful thing to look at, for the reasons they set out - they give you an understanding of how the bike will feel, particularly when they are shown relating to road speed as well as revs - then you can see which gear works at what speed.

It is possible to design an inline four with torque in mind. My XJ6 has a motor re-tuned for just that. The torque curve is pretty flat, and combined with relatively low overall gearing - it hits the red line in top at just under 120 (GPS-corrected) MPH - it drives surprisingly well in the high gears which makes it a doddle to ride on the road. For a work bike, that's just what I want and need.

Frankly, a bike with this kind of engine characteristics makes far more sense for ordinary road use than a much more powerful, peaky bike like the R6 that donated the motor to the XJ.

[The Spin Doctor]

I remember those....I thought I'd imagined it, cause whenever I've looked in bike mags recently (not that often TBF) they didn't have them. ISTR it was standard practice in the oft repeated 600 shootout etc.

If I may beat the same old drum again: EVs will change all this. They'll give you maximum thrust across a huge speed range with no need to change gear.

I first saw them in Motorcycle Mechanics which morphed into Performing Berks.

But not seen one for a long time. Unfortunately, if the mags (or online articles) don't explain why thrust curves are so useful, no-one looks at them because they don't understand them. But give 'em a big BHP number and they get all excited.

As I've said before, how much faster can you accelerate than a wheelie? It's not huge power that makes for fun, it's the gearing.

Re the electric bikes. The race bikes have had to use gearboxes, simply because there's a limit to how fast an electric motor can spin. Interestingly Kawasaki have been testing an electric motor / four speed gearbox set up. If I remember right it was seen shoe-horned into a Ninja 400... yes, just checked... I talked about it on my Elevenses webcast on April 24 last year. The rationale is that it allows the use of a smaller and lighter electric motor.

[Mr. Dazzle]

Quite right - maximum motor RPM is one of the big limits. That's why a Tesla with 700bhp still tops out at 130mph. Most EVs have a single speed gearbox and hence hit the redline long before they run out of power. Some of them now have twin speeds though so they can go really fast (I think Tesla have topped 200mph now).

A big big part of my job now is figuring out how to make the motors spin faster so that you can have high speed and still only have a single speed box thus saving weight. Faster electric motors also tend to be more efficient.

EV motors are getting pretty exotic now, full of carbon fibre and fancy processes. They're not as glamorous as a Ferrari V12 or a MotoGP V4, but it's where all the big money and tech is going for obvious reasons.

[The Spin Doctor]

Quite right - maximum motor RPM is one of the big limits. That's why a Tesla with 700bhp still tops out at 130mph. Most EVs have a single speed gearbox and hence hit the redline long before they run out of power. Some of them now have twin speeds though so they can go really fast (I think Tesla have topped 200mph now).

A big big part of my job now is figuring out how to make the motors spin faster so that you can have high speed and still only have a single speed box thus saving weight. Faster electric motors also tend to be more efficient.

EV motors are getting pretty exotic now, full of carbon fibre and fancy processes. They're not as glamorous as a Ferrari V12 or a MotoGP V4, but it's where all the big money and tech is going for obvious reasons.

Sounds fascinating, actually. I'm excited by EVs. But I guess I'm weird... or is that wired?

[Le_Fromage_Grande]

I think the disliking inline 4s is more of a disliking modern Japanese motorcycle inline 4s because they're tuned for maximum power and have little fly wheel effect, my 1170 Kawasaki has tons of torque and it's all low down as the redline is 9500rpm, with flat slide carbs you get instant torque at the back wheel from pretty near tick over, it also helps that the bike is quite light, I'm not sure what it weighs, but it's got no road going gear, a lightweight exhaust and the air cooled engine weighs less than a modern water cooled engine (using the age old "fuck me that's heavy" test)

[The Spin Doctor]

I think the disliking inline 4s is more of a disliking modern Japanese motorcycle inline 4s because they're tuned for maximum power and have little fly wheel effect, my 1170 Kawasaki has tons of torque and it's all low down as the redline is 9500rpm, with flat slide carbs you get instant torque at the back wheel from pretty near tick over, it also helps that the bike is quite light, I'm not sure what it weighs, but it's got no road going gear, a lightweight exhaust and the air cooled engine weighs less than a modern water cooled engine (using the age old "fuck me that's heavy" test)

Wouldn't a heavier flywheel actually slow down acceleration?

[Mr. Dazzle]

Wouldn't a heavier flywheel actually slow down acceleration?

It would, which is why you fit lightened ones in race vehicles. Downside is less refinement.

Older, slower revving bikes tend to be more grunty 'cause they're long stroke engines. Longer strokes mean the crank has a longer lever arm, so the same force from the piston is more torque on the crank. The downside of that is that it's harder to rev high and get big power. My old Triumph has a really long stroke motor, so it's got lots of bottom end but also tops out at <7000rpm.

[Le_Fromage_Grande]

I think the disliking inline 4s is more of a disliking modern Japanese motorcycle inline 4s because they're tuned for maximum power and have little fly wheel effect, my 1170 Kawasaki has tons of torque and it's all low down as the redline is 9500rpm, with flat slide carbs you get instant torque at the back wheel from pretty near tick over, it also helps that the bike is quite light, I'm not sure what it weighs, but it's got no road going gear, a lightweight exhaust and the air cooled engine weighs less than a modern water cooled engine (using the age old "fuck me that's heavy" test)

Wouldn't a heavier flywheel actually slow down acceleration?

In theory yes, but on dirt bikes a lot of people like the way a heavier flywheel feels (you can buy fly wheel weights for popular MX bikes), I don't understand the physics of it but it makes an engine feel like it has more mid range power when the reality is that it has less because the engine has more weight to spin round, the same seems to work on tarmac bikes, well it does for me - and this is purely my opinion, there is no science to back this up.

[Mr. Dazzle]

It's probably 'cause a heavy flywheel also works to prevent revs dropping quickly for exactly the same reason it stops them rising quickly. So if you start to get bogged down you sort of 'steamroller' through and keep the revs up. Particularly useful on a big single which has large gaps between power pulses.

[Le_Fromage_Grande]

Wouldn't a heavier flywheel actually slow down acceleration?

It would, which is why you fit lightened ones in race vehicles. Downside is less refinement.

Older, slower revving bikes tend to be more grunty 'cause they're long stroke engines. Longer strokes mean the crank has a longer lever arm, so the same force from the piston is more torque on the crank. The downside of that is that it's harder to rev high and get big power. My old Triumph has a really long stroke motor, so it's got lots of bottom end but also tops out at <7000rpm.

Or it could be this, my Z is an old fashioned long stroke engine, though it is quite over square, 75mm x 66mm, the CB1000R is 75 x 56.5, which is interesting as it's nearly 10mm less stroke, it's going to feel revvy.

[Le_Fromage_Grande]

It's probably 'cause a heavy flywheel also works to prevent revs dropping quickly for exactly the same reason it stops them rising quickly. So if you start to get bogged down you sort of 'steamroller' through and keep the revs up. Particularly useful on a big single which has large gaps between power pulses.

That's what I've always thought, but as I said there's no science to back it up.

[Mr. Dazzle]

Or it could be this, my Z is an old fashioned long stroke engine, though it is quite over square, 75mm x 66mm,

The Triumph is 71mm bore and 82mm stroke revs? What are revs?

[Le_Fromage_Grande]

Or it could be this, my Z is an old fashioned long stroke engine, though it is quite over square, 75mm x 66mm,

The Triumph is 71mm bore and 82mm stroke revs? What are revs?

That's going to feel lethargic, but you'll never need to change gear.

[Tricky]

[Dodgy69]

That Pan don't arf fly.

[Taipan]

That Supercharged CBR!

[Mr. Dazzle]

Yeah I was surprised to see that the Ducati still pulled away!