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Old 03-06-2012, 07:18 AM
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Beater Beater is offline
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Join Date: Dec 2005
Location: denver
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fcr's are a great carb, and I wouldn't get too far into them. They are THE defacto racing carb, and I have a set on the ducati. FWIW, a set of 41mm's goes for as much as 1300, and work off the shelf.

Before I would get into the pump, I would work with the jetting. The FCR usually has no choke or idle circuit per se. Some do not come with a low rpm air screw, others with a jet.

There are tuning manuals out there on the sudco site and others. Trust me, this carb is about jetting. I has razor sharp response, and distinct flow ranges of the jets.

All modern bikes come lean from the factory if they are carbed.

One serious piece of advice. Don't do any more mods until you reach normal temperatures. Again, the fcr is a precision toilet bowl. you need to jet and tune this for the ambient range and mean altitude you will be riding in. There is NO room for error in this carb. Due to the lack of screw adjustments, there is no on the fly.

I have found that airboxes are generally a good thing on modern four strokes. air pressure really helps low end performance, and real world riding is all about low end performance. On the duc, I do not have an airbox lid, but retained the lower portion. best of both worlds, but I sacrifice some "roll on" performance for peak performance.

Another trick with FCR's is to run a heavily soaked pre-filter to help richen the mixture in colder weather. If it warms up, or you increase altitude, just remove it.
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