1985 atc250es timing chain???

[hewlett2002000]

i have a 1985 atc250es, runs great but is has bad plastics, it was used for work. it runs great and has plenty of power but it has a vibrating noise in the engine, somebody told me that it was a loose timing chain but i need another opinion, if it is a loose timing chain will this hurt anything? its really bad when the engine is under a load like going up a steep hill or muddin or just high RPM's. please help. thanks. John

[hewlett2002000]

when you have the engine movin pretty fast it does vibrate. it is coming from the head, or jug or whatever(im good with cars, never really messed with small engines). its like a rattling noise in the top end of the engine. how do you adjust the tension? thanks for the help,
John Wright