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<blockquote data-quote="69ST" data-source="post: 1590" data-attributes="member: 5"><p>Trailpunisher's results point out some interesting details.</p><p></p><p>With the exception of the 48cc bike, all of the speeds are about what I'd expect. But notice the sprocket combos used. These indicate wide variations in transmission gearing between the different engines. That overacheiving L48 is pulling through a 14/36 combo, while the Z108 did best with a 14/37 (as with the Z124). I ran a Z108 with 17/33 sprockets, which yielded 6.76mph/1000rpm and the bike topped-out at 57/58mph on the flat, exactly matching the 8500rpm hp peak of that specific engine. If the transmission ratios were the same, then top rpm should be 24% greater (10,700)...not possible with the cam used, which had a 9600rpm upper limit. Obviously, the engines were spec'd differently from the manufacturer. If you know the rpm at which peak power is reached, engine redline and overall gearing through the transmission, then you can science-out the gearing without a lot of trial and error. Short of that info, a tachometer is the next best thing. This is what I was trying to point out in another thread.</p></blockquote><p></p>
[QUOTE="69ST, post: 1590, member: 5"] Trailpunisher's results point out some interesting details. With the exception of the 48cc bike, all of the speeds are about what I'd expect. But notice the sprocket combos used. These indicate wide variations in transmission gearing between the different engines. That overacheiving L48 is pulling through a 14/36 combo, while the Z108 did best with a 14/37 (as with the Z124). I ran a Z108 with 17/33 sprockets, which yielded 6.76mph/1000rpm and the bike topped-out at 57/58mph on the flat, exactly matching the 8500rpm hp peak of that specific engine. If the transmission ratios were the same, then top rpm should be 24% greater (10,700)...not possible with the cam used, which had a 9600rpm upper limit. Obviously, the engines were spec'd differently from the manufacturer. If you know the rpm at which peak power is reached, engine redline and overall gearing through the transmission, then you can science-out the gearing without a lot of trial and error. Short of that info, a tachometer is the next best thing. This is what I was trying to point out in another thread. [/QUOTE]
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