
and also the documentation from the factory nominates (with
embarrassment) a value of 5.75 = 1, which corresponds to the
compression value at the exhaust port point.
A high
compression ratio in the case of a twostroke means, when it is
healthy in other ways, only a very noticeable thermic relief of the
exhaust area and with that, better concentric stability of the
cylinder. In fact the MB 250 has a total compression ratio of
7.8:1 to 8.0:1. Therefore even with normal petrol under the
strongest uphill load or under acceleration it shows not the
slightest inclination to ring.
The impressive maximum speed, which, in spite of many doubts,
represents an undisputed performance benchmark, and which here
proves very obviously that the low riderseat and, as a consequence,
the slightly stooped position giving a reasonably noticeable
lowering of the area of resistance, is not the strongest impression
of the test.
Even more convincing is the very exceptional acceleration for a
quarterlitre machine , which by appropriate use of the gears, can
keep up with most halflitre machines. From a standing start,
80 km/h is achieved in 10 seconds and 100 km/h in 20 seconds, when
one drives the gears out to a good 6000rpm. That is 35 in the
first, 60 in second and 85 in the third. Here becomes evident
the excellent torque of the MB 250, the peak of which with 2.14mkg
at 5200rpm lies somewhat high, which between 4000 and 5800rpm,
however, stays over 2mkg . 