Hi Folks,

I was reading an article in a recent MCN about the new A2 Licence limits, and it got me thinking. Apparently the new A2 Licence permits riders to ride a new category of bike restricted to power output of 47bhp. The DSA (Driving Standards Agency) publishes a list of motorcycles which are sutable for the new A2 test.

According to the article, this includes the XT660R and the XT660Z Tenere, but NOT the XT660X Supermoto. Why not?? So, browsing through a copy of Yamaha's "Street 2012" brochure I find the specification quotes engine output of the XT660X at 48bhp - just one bhp over the new limit! However, not having an off-road brochure to hand, I couldn't find a comparable figure for the XT660R or XT660Z. Anyone happen to know what the Yamaha quoted bhp figure is for those? Obviously it must be under 47bhp, but how much under? Why are the XT660R and XT660Z engines less powerful than the Supermoto? And what is the difference down to? Different timing? Different fuelling? Less restrictive exhaust?

I was intrigued by this, so can anyone shed any light on the subject?

The XT660X is A2 license friendly...

http://www.yamaha-motor.eu/uk/produc...et/xt660x.aspx

All the 660 engined bikes are, R, X, Z and MT-03

Just another government error!

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Ah, thanks Pleiades.

So they do all have basically the same engine after all, and it's rated at 35.0 kW. The A2 limit is also 35.0 kW.

Apart from the XT660X being left off the list of A2-friendly bikes, it appears my confusion came from the horsepower conversion.

Apparently 48 PS is not the same as 48 bhp - I always thought it was near enough to assume 1-to-1 conversion. But after a bit of hunting for conversion factors I found:

Using the conversion 1 horsepower = 0.7457 kilowatts = 1.0139 PS,
then 35.0 kW converts to 46.9 bhp or 47.6 PS.

Cheers!

I think that's where the mistake in the DSA list originally stemmed from. All motor manufacturers quote power in PS (or kW) these days, thanks to the EU. Britain is one of the last bastions of horse power, but as we have no home-owned motor industry any more (Triumph excepted) we don't carry the same sway as we used to.

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Yeah, stupid really, because PS (Pferdest�rke) simply translates as "horse power" anyway. But the PS or "metric horsepower" is slightly optimistic compared to "imperial horsepower" or BHP (by 1.4% as I mentioned above).

So Yamaha's figure of 48 PS, which they conveniently rounded up from 47.6 anyway, converts to 46.9 bhp and therefore comes within the A2 limit.

More info on Wikipedia if anyone's interested.
http://en.wikipedia.org/wiki/Horsepower

Anyone has an idea why the Aprilia Pegaso 660 has to be restricted? It has the same engine, but it is not A2 friendly.