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Old 05-18-2010, 09:22 AM   #1
Join Date: Sep 2008
Location: San Antoino, Texas
Posts: 4
Default 8.5 vs 12.5 Carb

Both carburetors I own are 8.5's with the proper jets and floats. But, I've been reading that the 12.5 insert may provide better performance on larger tracks with long straights and few tight corners. Plus, I like the idea of having the two different types so we can test with both.

We don't road race so when I refer to a larger track I talking about a track like Norman, OK where Nationals were held last year.

Comments / suggestions?

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Old 05-18-2010, 10:55 AM   #2
Marc Miller
Birel & Rotax Specialist
Join Date: Jan 2008
Posts: 850

Hi Patrick,

Changing your 8.5 insert to a 12.5 venturi is not as dramatic a change as going from a 30-pilot to a 60-pilot but does provide more fuel on the bottom end, which usually means you will need to run a smaller main jet.
Marc Miller
Director of Brand Development
MRP Motorsport/Birel
Marc Miller is offline   Reply With Quote

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