i've got an older fh500v that started knocking this summer. i didnt have time to open the case so i just ran it, and it didnt really get any worse after a certain point. it seems to only knock when its under a heavy load, worse when cold. theres certain engine speeds where it wont make any noise at all and it sounds perfect. it almost sounds like a really deep pitched rattle and you definitely cant miss it. so i split the case open and i expected to have the problem be really obvious but everything inside seems pretty decent. theres some obvious wear to the governor. the connecting rods seem to be a little loose but i cant imagine their loose enough to make the sound it was making since it was intermittent. the main bearings are tight, but the crankshaft did have a bit of up and down endplay, will a crank bounce up and down under the right conditions and make a knock? any ideas?