lance missile , why do the spin thrusters smoke ?

i have just downloaded a collection of rocket / missile images . and the spin stabiliser thrusters [ i assume thats what they are ] on the lance missile smoke like a diesel tractor .

why is that ?

the main rocket motor appears to be quite clean burning .

and spin stabilisers on rockets like the " honest john " burn far cleaner - with only a pup of particulates on ignition .

so why do the lance thrusters emmit so much smoke for soo long ?

here is a picture of lance with " dirty thrusters "



and honest john [ clean thrusters ]