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Justin Arruda

2004 Yamaha YFZ 450 Big Bore Kit

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Posted (edited)

Hey I’m looking to put a big bore kit on my atv I was wondering if anyone knew how big of a jet I would need to put in my. Carb so the atv would run good 

Edited by Justin Arruda

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There's no real magical cubes = jet sizing formula.  Given that every motor is a bit different with it's own personality you just have to do some trial and error.  Seat testing, plug chops.  To really tune it just takes a bit of time and testing.  Take into account type of exhaust, air filter type, airbox or not, elevation, fuel type, pilot and main jet setting, needle clip position, fuel screw position.

I did some google searches and a few people have asked the same on some Yamaha specific forums, so maybe you can find something to get you close.

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