Clones are made for these carburetors that are adjustable. They'll have 3 adjustment screws. Replacing a jet won't be necessary. What you'll need is a tachometer to set the adjustments and a metering lever adjustment tool. You'll also have to adjust it at the altitude you plan to be riding in.
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Your biggest issue will be you're taking a friction drive into a mountainous region. Depending on the total weight (bike, rider, cargo) you may find it impossible to get up really steep hills.