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Holding back the gears

The relationship between gear ratios, torque, thrust and 'retuning' is never an easy one

Honda's new CTX1300 is, at first glance, technically unremarkable. It is, essentially, a stripped-down, half-faired Pan European with sharper steering, a wider rear tyre, a stereo and, somehow, more weight. It has the same 1261cc transverse 90° V4, 'retuned' for more midrange.

But the spec shows this is more, or less, than a retune: a stock Pan makes 125bhp at 8000rpm and 92 lb.ft at 6000rpm. Honda say the CTX makes 83bhp at 6000rpm and 78 lb.ft at 4500rpm. That's a massive 40% less peak power and 16% less peak torque!

Doubtless the curves are reshaped, but it's still a big deficit. Why Honda has done this will be revealed...

Clearance approved

Why it’s important to have room at the top, especially if you’re a valve

MCN reader Ron Smithson emailed with two questions: “Re: Honda’s CB500 range having a 600-mile valve clearance check; imagine the furore if a new Honda Civic (30,000 miles) was the same? Why’s a bike engine different?”

The second question has a straightforward answer...

Going off at a tangent

Why steering geometry is never a straight ahead subject

Indian’s new Classic, Vintage and Chieftain share engines and frames, differing only in trim and styling. Yet while the Classic and Vintage have identical chassis spec, the Chieftain has different numbers: 61mm less wheelbase, 4° steeper rake angle and 5mm less trail. If you were to judge which Indian was sportiest on spec, you’d say the Chieftain. Which is odd, because...

No more crank calls please

Do Yamaha’s new MT-09 and MT-07 really use R1-style crossplane technology?

Lots of people get cross when Yamaha claim their new MT-09’s 850cc inline triple and MT-07’s 689cc parallel twin are crossplane engines. How can they be? They don’t have enough pistons.

The crossplane idea works like this: in a conventional inline four the pistons move in pairs, two up, two down. When the middle pair are at top dead centre, the piston either side is at bottom dead centre. They fire evenly, every 180°, 1-2-4-3. This layout has perfect primary balance because piston pairs move in opposition, but....

Seat of the pants stuff

The science of sitting comfortably is harder than it looks

For a manufacturer, technical challenges aren't all cutting-edge electronics and active suspension. And it's easy to dismiss cruisers like Triumph's new Thunderbird Commander and Horizon LT as low-tech and simple to design. But they have their own challenges like, for example, making a comfy seat. It sounds easy: make it comfy. But there's more to it than that....

In the overlap of the gods

Making one engine fit many roles is all about getting the timing right...

What’s the similarity between Ducati’s 2009 1198 superbike, the Multistrada, Diavel and new 1200 Monster? Yes, they share versions of the 1198cc Testastretta engine. The versatile V-twin has gone from sportsbike to adventure bike to power cruiser to naked in just five years.

You’d think their disparate riding dynamics couldn’t be achieved with the same engine. So how does the 1198 Testastretta fit such different roles?....

Tough Torque

KTM’s 1290: why they call it PR ‘spin’

KTM test rider and ex-500cc GP racer Jeremy McWilliams says the new 1290 Super Duke is the torquiest bike he’s ridden. KTM claim it makes more at 2000rpm than the 990 Super Duke at peak (70 lb.ft). That’s a lot of big torque talk.

Torque is often wrongly thought of as a measure of engine performance at low rpm. Big V-twins have ‘lots of low-down torque’, and inline four sportsbikes ‘lots of top-end power’, as if the two are discrete and opposite. They are different, but not opposites...

Compounding: The Problem

Ever wondered why your rear tyre wears down in the middle but not at the sides? It’s safer that way...

At first glance there’s nothing in common between touring on a Triumph Tiger 800 XC and a 250bhp MotoGP prototype. But there is.

I recently had a 3000-mile ride on a Tiger. Its Bridgestone Battlewings were 4000 miles-old at the start and, as you’d expect, the rear squared-off as the ride went on. 7000 miles isn’t a bad total, and the bike maintained its steering and stability. But eventually it shimmied a bit over white-lines as it rolled across its squared-off centre. And with plenty of tread left on the edges, it seemed a waste of rubber to chuck it away.

So why don’t manufacturers make rear tyres harder in the middle where they wear the most?...

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