My late Spitfire daily-dog just-consider-it-a-mildly-crash-resistant-
motorcycle-that-doesnt-fall-over has an electric fan, so there's no
relationship between rpms and fan contact.
Nevertheless between about 4200 and 4500 rpm it sets up a loud buzzing
under hard acceleration.
I believe it's because US-spec 1500s, among other lamenesses, have
only single valve springs instead of the doubled springs used in
Eurospec Spitters. I suspect that at these revs I'm hitting the
harmonic values of these springs and causing them to buzz.
Acceleration gets very weak in this range, but straightens out above
4500, coincident with the point where the buzzing stops.
Any thoughts on this? I understand that the doubled spring arrangement
was used precisely because of this problem...I read it somewhere...
- Dan
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