When recrystallizing methylamine hydrochloride from methanol, I have found it to be very effective to dissolve the crystals in a minimum amount of boiling methanol, then allowing the solution to slowly cool to room temp, then to 5-10°C in the fridge, and finally to -15-20°C in the freezer before vacuum filtering and then washing the crystals with a very small amount of freezer-cold isopropanol results in very pure, spectacular thin plates (usually up to 1x1 cm) of methylamine hydrochloride. Drying the crystals in a dessiccator over KOH completes the process.
The filtrate gotten after the filtration can be diluted with an equal amount of isopropanol and again cooled in the freezer to give another crop of slightly less pure crystals, maximizing the yield without having to concentrate the alcoholic solution by evaporation or distillation, and without having to introduce any acetone anywhere in the process, which potentially can react with the MeAm.HCl, forming acetone methylimine...