I´ve heard 2 sides of the story. One says to replace everything - chain and sprockets. The other says if the sprockets are not worn, then replace just the chain (2 chains/1 sprocket set).

I´ve ridden almost 29,000km on my bike and it´s time to replace the chain. But, as you can see in the pics, the rear sprocket still looks good (plz, say if it doesn´t to you). The front sprocket has a wavy pattern, because the dealer mistakenly adjusted the chain slack and I only noticed it when I saw that pattern on the sprocket. It´s been like that for the past many thousand kilometers. The teeth tips are all square on both sprockets.

I am considering replacing only the chain and front sprocket. Maybe just the chain. Opinions, plz?

 

Front definitely needs replacing. I'd do the back too just because I like new chains to go with new sprockets - but that's just me. I'm sure you would be OK without, but they're so cheap why not.

 

I think the rear sprocket looks good but would definitely replace the front one. They're cheap and easy to do.

 

Your front is toast. Better off replacing both sprockets. Save your lunch money, eBay has jt steel rears for $28. Renthal aluminum for $30 more. It will save your new chain

 

I agree it´s too cheap to not replace it. Although, the exchange rate down here is 1:2.
I guess I´ll just do it, then. I´ve checked ebay, but couldn´t find any 39T sprockets for the KLX. At least, I found JT 39T on Amazon.

I am thinking on trying a D.I.D. X-Ring chain, instead of an O-Ring. D.I.D. is a good brand, right?

 

I consider myself to be ‘prudently economical’ when it comes to maintaining my bikes, but I wouldn’t waste my time or money partially replacing elements of the final drive system. Especially if they’ve already got 29,000km on them. At that point, they don't really owe you anything anymore.

The rationale is that the worn pitch of old parts will not mesh properly with the pitch of new parts resulting in inequitably-distributed loading of the sprocket teeth & chain rollers, which in turn results in premature wear of the new components.

 

My DRZ chain and sprockets were worn out to the point that the front end of the bike felt jumpy at low speed, it was terrible.

My rear sprocket was also in similar condition to yours... I did both though, just to be safe... rear sprocket was only $36 at the local shop.

 

Good post. Common sense put into a blender and blended into an easy to understand shake. Never really understood the rationale behind replacing everything at once.