Thank you for your replies ,I have fitted two DZ126 decoders and matched the power to each on the front chassis I increased the start voltage (CV02) to 015 so that on speed 1 the wheels just start then isolating this from the track I set the rear chassis (CV02 ) to 010 so that on speed 1 the wheels just started to move ,then with both chassises on the track I found that they both started at the same time I then set the mid voltage on both decoders (CV06) to 020 and the maximum voltage (CV05) to 060 as these loco will not run fast like an express train.
When I was happy with the way it performed on the rowing road I renumbers the decoders to 143 to match the engine number of the K1 Garrett on the welsh hi land railway.