friction disc on your machine has about 3/16 inch of rubber on a steel ring.
if worn to less than 1/8 performance will suffer.
a quick check is to put it in the gear it slips in and then squeeze the engagement lever ,if it dosent move then try giving the cable that the lever operates a little tug while the lever is depressed.
if the machine moves then you may just have to adjust it.
on your machine i beleive there is a spring at the bottom of the cable.you will have to remove the cable from the lever at the top then slide the cable back through the spring and there will be an adjustment nut inside the spring on the cable.just go a turn or 2 at a time.you dont want to over do it or you will wear out the friction wheel to soon.
later chris
craftsman 10/28 snowblower with tracks husky 372xpg chainsaw sachs dolmar bc212 bushsaw mondo trimmer monster tractor with trailer cheep wheelbarro and couple shovels and a partridge in a pear tree