Chains don't stretch. They wear. The wear is greatly accelerated if the chain is too tight when the suspension is compressed.
WD-40 is an extremely weak lubricant. Just about any other lube works better. It is OK for cleaning. Try PG1 Blue or the $5 DuPont Teflon multi-purpose stuff from Lowes (blue can).
This link to EK chain shows that there is a non-sealed roller over bushing. The o-ring (x-ring, whatever) holds in the lube for the pin & bushing, but not for the roller. Roller and sprockets need lube for longest life.
http://ekchain.com/seals.htm
WD-40 is an extremely weak lubricant. Just about any other lube works better. It is OK for cleaning. Try PG1 Blue or the $5 DuPont Teflon multi-purpose stuff from Lowes (blue can).
This link to EK chain shows that there is a non-sealed roller over bushing. The o-ring (x-ring, whatever) holds in the lube for the pin & bushing, but not for the roller. Roller and sprockets need lube for longest life.
http://ekchain.com/seals.htm