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Familie Wantij
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Norton Commando 750 Interstate MKIV 1972 |
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| The 1972 Norton Commando came with an option on the Commando Roadsters
& the new Commando Interstate for a 'hotter' 64 horse power engine,
called the Combat. All Combat engines came with their cases painted black.
The advertised extra 5hp came from a bump in compression ratio to 10.0:1
(by shaving the head surface), larger 32mm Amal 932 Concentric
carburetors, larger intake tracts to match & a wild high-lift,
long-duration cam. The engine proved to be "peaky", with good
power in the upper rpm-range, but not so good in the low- & mid-range.
So, they geared it down with a smaller front sprocket to help
acceleration. This meant it would top out at 108mph at 7,000 rpm, not
exactly what you'd expect from a racing engine. This low gearing made it
all to possible to over-rev the engine, even in top gear. The pistons, the
same slotted versions used since the Norton Atlas, worked fine at
5,000rpm, but at 7,000 under extreme loads, then tended to pull the crowns
loose from their skirts. |
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