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The latest dyno run was done on the new Scooterlabs dyno, which is a dyno setup to read true rear wheel HP (not estimated at the crank). On previous dyno runs I had issues with mapping the rpm correctly due to various reasons (e.g. dyno setup for standard Vespa gearing and then I hop on with my long gearing). Also all dyno runs were done in third gear. So the lab session was to do a few things:
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Wind her out in 4th gear and see what the top speed is based on mph alone (not post-calculated from rpm)
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Do the dyno with the tyres pumped up to race pressure
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See how the tyres handle 100mph
The results:
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Blue is 3rd gear, Red is 4th gear. Even with a Malossi 24/63 upgear, the current peak power (32hp) is at ~86mph (7500rpm) fading out (21hp) at around ~95mph (8500rpm). With no juice at all by 100mph (just under 9000rpm).
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The increased tyre pressure and reduced rolling resistance gave a peak power of 32hp at the rear wheel (which on dyno's that estimate crank hp would read 42hp)
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The rear wheel (and the rest of the motor) handled the speeds fine
Note: I estimate that 25hp is required to do 100mph
Conclusions:
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Get a
DRT 33 Tooth Long 4th Gear
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A better and shorter carb manifold which is less restricted will push out the top end rpm
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The super charger planned may also push out the top end
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Maybe a 35mm or 36mm carb would improve power, the 38mm may(?) be too much. Though with a super charger probably not
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Maybe alter the expansion chamber to drop the top end power more slowly (diffuser taper angle) or target higher rpm (length)
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