Check that it is the cable first, it should be easy to see if the cable is sticking for either the hot start or the de-compressor. Make sure there is some free play in the de-compression cable/ lever other wise you are lowering the compression all of the time.
if the hot start is sticking it will be letting more air through than is required, ussually when they cough and fart it is due to too much air in the fuel mixture.
if the cable is not running free in the outer cable, take it off and hang it up, tape the top end to form a funnel and spray a pool of wd 40 or similar into the funnel an