Go back and check the wattage of the bulbs that are fitted to the indicators you replaced, Now check the wattage of the bulbs in the indicators you have just fitted.
If the ones fitted are quite a bit higher in wattage then thats more than likely the problem, The indicator relay fitted to your bike is only designed for a max loading enabling it to flash at the correct rate..
If this is the case then you've got two options.
Fit the old bulbs in your new indicators. or
Purchase a relay up to flashing your new indicators with the new bulbs.
Another reason indicators may not flash is loss of an earth or poor earth.