Inefficiency and Power losses?

Guys,

I always looking in old scrapbooks of stuff P have looked into and the other day I came across a old link to a dyno'ed K75.
I cannot find the main original article but it essence it was about power losses experienced through a stain/staytune exhaust system , anyhow the outcome was even when breathing at its best with stock exhaust the K75 seemed only to be producing around 52 bhp at the rear wheel, this means that the power losses from the crankshaft to the rear wheel are much more than the theoretical 10% for a chain-driven bike and assumed 15% for a shaft-driven machine, it all started with an owner complaining that his K75 was having problems keeping up with a 50bhp BMW horizontally opposed air-cooled twin!

This puts the K75 in the arena of the big parallel twins of yesteryear , is it right that there is such a huge % loss between the crank and the rear wheel and if so what's the main culprit?

This is a nice little article too.
Also:
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Cheers

JBW

Guys,
I found the link <!-- m --><a class="postlink" href="http://www.eilenberger.net/k75exhaust/" onclick="window.open(this.href);return false;">http://www.eilenberger.net/k75exhaust/</a><!-- m --> and it was in fact a 60 bhp R100 Mystic !
There also was an article commenting on the lack of torque produced by the K75, relative to the fact that the cylinder displacements given, however, I believe someone pointed out that the K75 engines had two different sets of flywheels fitted and in fact if I remember rightly, the the earlier bikes had a heavier flywheel arrangement, I presume this fact is correct?

Cheers

JBW