F7A/B Speed Difference

[Kelly]

I have just purchased a brand new N scale Spectrum F7 A/B set. When speed matched, spaced 6" apart, the A unit is much faster than the B unit. Is this common or is it a problem? I am worried that I might ruin the A unit motor if it has to do the work of pulling the rolling stock as well as the B unit.
Thank you,
                 Kelly

[David Leonard]

I suggest running both units (separately at first) to allow them to break in. It could be that the B unit needs more break-in time. If that doesn't help, then maybe someone else has some ideas. If nothing else helps, however, you could always switch shells (and front trucks & light board) and make the B unit the faster one.