I have two new Bachmann n scale locos (with dual mode decoders) that won't run in straight DC. The first is an RS3. The light comes on but the loco does not move at any voltage. The 2nd is a 44 tonner that will not run at low speeds but will jump to life at maybe 50 scale miles per hour when you really crank the throttle up and give it a little shove. I have a MRC Tech II power pack with the momentum turned off. Kind of sucks that these "dual mode" decoders won't work as they should. I have no access to a DCC system so what do I do?

Added: I have another Bachmann RS3 with the dual mode decoder that runs perfectly with good low-speed performance. I tried them all with an old Revell power pack with pretty much the same results. I know that the dual mode decoder will require more throttle input than a DC loco but that 44 tonner starts jerking ahead until a high enough voltage is reached and then it sprints down the track at the moment the right voltage is reached. It's almost like the decoder is giving quick shots of voltage because the light flickers on and off when it is jumping and then goes steady when it takes off at warp speed.  I'm wondering how hard it would be to eliminate the decoder completely and make these straight DC locos for now. Would I lose the nice bright lights?