boost bottle


Yamaha's have such short intake tracts that it doesn't have near the effect that it does on the Polaris twins, especially the big blocks. Take notice the next time you see a polaris engine, they have much longer intake tracts, and that creates more room for leftover fuel charge that was being accelerated towards the reeds before they slammed shut, so some of that excess is transferred over to the other cylinder, so it is ready to enter the crankcase as soon as the reeds open, whereas it takes a split second for the charge to be drawn from the carbs. The difference is also more noticeable because the big twins have a lot more volume per cylinder to fill on each intake/compression than the triples which have much smaller volumes per cylinder. The twins have to fill more volume in the same amount of time, so they get added benefit if the charge starts entering earlier.
 
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