Inliners International Forums General Discussion Engines Why won't the spark plugs fit?

That R44XLS is the part number I used. All the cross references showed the same size plug in different brands. I am going to go back to the store today and look in all the books and see what I can come up with.

I figured it was an older head. Is the older head better than the newer ones? From the chart seems like it flows better, but could be wrong.