I have barnett springs and dirt racer clutch on my 351 klx, the clunk has always been there even before the upgrade, clutch basket looked good to me. I've always assume it's been a drive chain issue, perhaps the feeling of the chains initial friction on the sliders, depending on what gearing you are running.

 

The clutch doesnt feel like it is slipping, it doesnt quite grab as well as it used to, but i have never had the bike lose power, and spike on the revs. As for chain tension, I am not very knowledgeable on adjusting the chain. I've got an old timer that I ride with that was with me when we adjusted the chain last. What is the easiest way to correctly tension the chain?

 

Check the manual to adj your chain. Many bikes are different due to exact connection locations.

 

Right... the manual. I have one of those. * searches for manual *

 

The danger of an over tightened chain is that when your rear suspension is compressed about 2/3 through it's travel is when your chain gets it's tightest. The absolute best way to check is to remove your shock and adjust the chain so you can rotate your swingarm up through the motion. Not practical at all unless you were doing other maintenance, so I check at the back bottom of the plastic chain protector that is mounted to the front of the swingarm. Push the chain up and it should come to about 10mm from the swingarm. Then compress the rear suspension and make sure it doesn't get super tight and then you're good. I don't have a manual, but this is the basic way with all bikes, unless of course you own an ATK 406.

 

I always adjusted mine to touch the screw at the bottom of the swingarm chain slider, I'd rather be slightly too loose than too tight