what are the stock spark plugs on the stock gs400? platinum or iradium? is it hard to change them?

 

I think they are iradium plugs that your running on gs400. What yr? Its easy to check and change!

Unscrew the pastic cover over the engine as well as the plastic piece on the valve cover. Plugs are located right in the valve cover, you'll need a long extension on your spark plug rachet though cause they are deep down! Unplug the wire from a cylinder and bingo you have located them. I know its not as easy as I typed but I hope you get the jist of it Pull one out and check to see what your running and then put it back in. Will take 15 minutes to check maximun 30!

Good luck!