Hi had similar problem years ago it was a 109 also,found that if you set shoes with cam as per book then take drum off you will find cylinder isnt touching heel of shoe as has retracted [so when assembled and you push the pedal it has to take up this gap first ] my remedy was to put in spacer so as tight in gap,no more problem after that,possibley mix of shoes and cylinders as quite a few different types.
