What is that rubber piece that goes under the chain it might be a chain guard to protect the swing arm I need to replace that piece any ideas I have a 04 honda cbr 600rr it's a little rubber strip and may have two groves into kt

"The rubber thingy on the swingarm"... that's the official Honda name for it.

But the Honda dealer doesn't have exploded parts diagrams on its Inventory system? They certainly do with the cars. Just give them the model and year, where it is and they can pull up an exploded diagram with reference numbers on each part... and lower the full part number and availability. All you need to do it point where it is, and you do know everything else you need.

Don't over-think it....it really is that easy...as long as you know what it looks like and where it goes...Year make and model is everything else you need to know at the parts counter at the dealer, and a lot of online places too.

03-04 honda cbr 600rr chain guard (Y33)
(on ebay?)

Maybe you tried ebay, because I don't see much that combines all words, especially the year.