Originally Posted by
ps2fixer
The chain is the part that likely has the most wear. Chains don't look ugly when they are worn, they stretch over time, the wear you don't really see visually. Since it's apart, a new chain is normally a good idea. Kind of like on a car, when you do a timing belt job, you also replace the water pump since you're already right at it.
I looked up the maintenance schedule and it seems like long didn't give a service life for the timing chain. I scanned around a bit and the only thing I found about the timing chain for checking it is inspect the slides for damage and make sure the tensioner is functioning correctly. I guess they pretty much are suggesting the chain is good for the life of the engine. Personally I'd replace the chain since they aren't normally too expensive, and you'll be good to go for 20+ years for internal engine work if all else is in good shape. The chain normally gives a nice warning when it's about to cause problems, it gets loose and you get a "timing chain slap" noise in the engine. I haven't really heard about them going bad on the 250es, but I've seen them go bad on the atc350x, trx250x and such and the past owners ignored them.
Does the cam chain slides have damage? There's going to be visible wear from the chain sliding on them. If there's excess wear it should be replaced.
Measure the cam and rockers, if they are in spec, they are good to use.