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Keihin FCR40

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Soooo - what do you DRZ experts think....the new RMZ450 comes with a Keihin FCR40 carb....is this something that we can make work on the DRZ??????

Would it be better than the FCR39??????? 👍

It would be really cool to beef up the power with that even better than the FCR39

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It would require more then just installing it. The head would need to be modified to take advantage of the increased bore.

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A bigger carb allows the air to flow thru the carb at a slower air speed because the air is not having to squeeze thru a smaller opening...this works great for high rpms where a large airflow is needed and the air velocities thru the carb increase enough to provide a strong signal and atomization of the fuel...but, the slower air velocities at lower engine speeds cause the engine to feel more sluggish and kills cylinder fill and power production. A CRF450 is designed for MX style powerband and revs very quickly into the upper rpms and can take advantage of the larger carb...A DRZ has a counter balance engine which gives it a stronger bottom end, but keeps it from revving as fast and thus would not feel the gains as much with the bigger carb until it was at the very top rpms. One other reason a bigger carb does not do well on the DRZ is that the DRZ cylinder wall is very close to the edge of the valves in stock configuration (called shrouding), this is one of the reasons a 440 kit works so well on the DRZ. It moves the cylinder wall away from the valves (unshrouds the valves) and allows the airflow to tulip around the valve and make much more power. :thumbsup:Andrew

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