Masters of Torque

[Scim77]

Does anyone know if the MT-07 is a desaxe design, like the MT-09? Most car and bike engines use desaxe to some degree, to improve torque and reduce internal stresses and friction. I have not found any Yamaha reference to it being used in the MT-07, although studying the workshop manual diagrams there does appear to be a cylinder bore mis-alignment with the crank pin.

This link shows the basic principle https://rideapart.com/articles/free-power-offset-cylinders-explained

In 1943 Phil Irving, who designed the HRD Vincent, calculated that a 76 degree crankshaft should also give the maximum torque with minimum imbalance for a twin cylinder engine. If the British motorcycle industry had heeded his words, we would not have wasted our time exploring the cul-de-sac of trying to balance the big parallel twins that Triumph, BSA and Norton were pursuing.

 

[sharky]

does this answer your question?

 

[Scim77]

does this answer your question?

View attachment 2440

Unfortunately not. But thanks for the great picture. We need to see a dimensioned engineering drawing, viewed from one end of the crankshaft looking axially along the crank towards the piston/cylinder/con-rod. If the MT-07 is a desaxe design, which I suspect it is, then when the main bearing, big-end and little-end are all in alignment, the conrod itself will be canted over slightly, to locate with the piston in the offset cylinder. Messy to describe but easy to figure from a drawing.
Yamaha make a marketing feature of this with their MT-09 three cylinder engine, since it is less common on multi-cylinder engines. It may be more commonplace on singles and twins, which is perhaps why Yamaha don't bother to mention it.
Engineering designers over a century ago knew about desaxe and used it in steam engines to improve torque and reduce friction. It is nice to see that we are still utilising this feature a hundred years later.
Maybe Yamaha will further improve torque by introducing a 76 degree crank in the next generation of engines

 

[robodene]

I am pretty sure it is desaxe layout. I'll see if I can find an article. PS. Cannot find a reference so I may be wrong.

 

[sharky]

have you had a look at the service manual?

 

[Scim77]

have you had a look at the service manual?

Yes. The only diagram I can find is in the "Lubrication System Chart & Diagrams" page 2-29. Unfortunately, it is not dimensioned. However, if you look very closely, the connecting rod does seem to be slightly off-centre in the cylinder bore when the gudgeon pin, big-end and main bearings are all in line.

 

[TJ63]

I understand it to be Desaxe (same as my wife's Hyundai i10)

 

[Scim77]

Thanks TJ63. I think you must be correct. In truth it would be almost inconceivable for the MT-07 not be Desaxe.

The over-centre advantages of Desaxe are too good for engine designers to ignore. As you point out, Hyundai have exploited it to the full in their i10. All interesting stuff!

 

[robodene]

I have just read that the MT-07 has off-set cylinders - on the Yamaha website.

 

[KEVINJSTANLEY]

bugger me there are clever people about, I would not care if there was a little pixie inside running on a cage ,all I care about is it starts and makes me smile. but fair do's no knocking your mechanical experience