CartanMatrix[A1]

Weights[A1,Irrep[A1][{3}]]=.
Profile[Weights[A1,Irrep[A1][{3}]]]

Table[AbsoluteTiming[With[{Γ=A1,λ={k}},
With[{V=Irrep[Γ][λ]},
(*Associator[Γ,V,V,V,FundamentalBasis]=*)Associator[Γ,V,V,V,FundamentalBasis]
(*Inverse[Associator[F4,V,V,V,FundamentalBasis]]=Inverse[Associator[F4,V,V,V,FundamentalBasis]];
Inverse[Associator[F4,V⊗V,V,V,FundamentalBasis]]=Inverse[Associator[F4,V⊗V,V,V,FundamentalBasis]];*)
]
];][[1]],{k,5,10}]

Profile[With[{Γ=A1,λ={15}},With[{V=Irrep[Γ][λ]},
Associator[Γ,V⊗V,V,V,FundamentalBasis]
]];]

Profile[With[{Γ=F4,λ={0,0,0,1}},With[{V=Irrep[Γ][λ]},
Associator[Γ,V⊗V,V,V,FundamentalBasis]
]];]

ListPlot[%]

Profile[With[{Γ=A1,λ={7}},
With[{V=Irrep[Γ][λ]},
(*Associator[Γ,V,V,V,FundamentalBasis]=*)QuantumGroups`RepresentationTensors`Private`RightAssociator[Γ,V,V,V,{1}]
(*Inverse[Associator[F4,V,V,V,FundamentalBasis]]=Inverse[Associator[F4,V,V,V,FundamentalBasis]];
Inverse[Associator[F4,V⊗V,V,V,FundamentalBasis]]=Inverse[Associator[F4,V⊗V,V,V,FundamentalBasis]];*)
]
]]