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Everything Dirt Bike
General Dirt Bike
Gear Ratios/Engine Resistance
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<blockquote data-quote="James" data-source="post: 94945" data-attributes="member: 2"><p>After discussing this with Big Dan, trying to rotate the countershaft with an impact and bump starting a bike are to different things (ratios).</p><p> </p><p> </p><p>From the PM...</p><p> </p><p>Hang on, doesn't bump starting technically have the reverse effect? Power/force from the engine vs the rear wheel.</p><p> </p><p>The debate is if the engine/countershaft has greater resistance in either 1st or 5th gear if you're starting from a standstill (under the engine's power/hitting a nut on the countershaft with an impact).</p><p> </p><p>Let's say that the bike's 1st gear has a 12:1 ratio and 5th a 4:1. Put the bike in 5th gear (4:1 ratio) and try to take off with the engine's power, it'll stall as the force required is to great (from a standstill). However if you push the bike wouldn't the ratio technically be 1:4 as the power's coming from the rear wheel and not the engine(every rotation of the rear wheel rotates the engine 4 times)?</p><p> </p><p>In 5th gear:</p><p>Engine - 4:1 - High resistance</p><p>Bump starting - 1:4 - Low resistance</p><p> </p><p> </p><p>Bump starting in 1st would have a 1:12 ratio, one revolution of the rear wheel would rotate the engine 12 times. Would it not take more energy/force/resistance to rotate the engine 12 times vs 4, by spinning the rear wheel just once (bump starting)?</p><p> </p><p> </p><p>In 1st gear:</p><p>Engine - 12:1 - Low resistance</p><p>Bump starting - 1:12 - High resistance</p></blockquote><p></p>
[QUOTE="James, post: 94945, member: 2"] After discussing this with Big Dan, trying to rotate the countershaft with an impact and bump starting a bike are to different things (ratios). From the PM... Hang on, doesn't bump starting technically have the reverse effect? Power/force from the engine vs the rear wheel. The debate is if the engine/countershaft has greater resistance in either 1st or 5th gear if you're starting from a standstill (under the engine's power/hitting a nut on the countershaft with an impact). Let's say that the bike's 1st gear has a 12:1 ratio and 5th a 4:1. Put the bike in 5th gear (4:1 ratio) and try to take off with the engine's power, it'll stall as the force required is to great (from a standstill). However if you push the bike wouldn't the ratio technically be 1:4 as the power's coming from the rear wheel and not the engine(every rotation of the rear wheel rotates the engine 4 times)? In 5th gear: Engine - 4:1 - High resistance Bump starting - 1:4 - Low resistance Bump starting in 1st would have a 1:12 ratio, one revolution of the rear wheel would rotate the engine 12 times. Would it not take more energy/force/resistance to rotate the engine 12 times vs 4, by spinning the rear wheel just once (bump starting)? In 1st gear: Engine - 12:1 - Low resistance Bump starting - 1:12 - High resistance [/QUOTE]
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Everything Dirt Bike
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Gear Ratios/Engine Resistance
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