timing chain

[fox400]

hello my 02 ex seems to have a clattering sound from the bottom end i was told it might be the timing chain is streched? is this a common thing with these motors? iv heard of people putting CRF 450 timing chains in? is this a big job that could cost me alot of money? i'm new to this stuff so just trying to figure it out
thanks adam

[j450rking]

it could be a timing chain. and yes the crf450 timing chain works and is stronger. it's not hard to do relly it just takes some time. you have to take the right hand side side case off and the clutch. and then you have to take the front plastic and gas tank off and take the top cover on the engine off. and then you have to take the cam gear off and remove the stock timing chain and put the crf chain on. it is best the get a clymer manual and that will tell you how to do just about everything on your ex