That guy at the Honda dealer is an ass. I tried this. You have to cut the 400ex pipe at where it Y's together and then manage to weld a piece on there to fit into the muffler and its not easy i gave up and said f- it, it wont look right at all. I bought a new head pipe from Honda last year for $97.00 and it was sweet went right on no cutting welding etc.
Justin
04 Trx 450r
85 Atc 350x
86 Trx 200sx
00 Xr 400R
85 Atc 70
98 Toyota Tacoma 4x4 xtra cab
99 400ex, 97 xr400, 85 Atc 110, 86 Atc 200x, 85 Atc 350X, 87 Trx 250X, 86 Atc 250R (mint), 78 Atc 90 all sold