on my k75s 1987 the rear tire is a 130/90/17 and i saw under the seat a plate that tell to put a 120/90/18, is it possible that i d`ont have the good rim for this bike?

The K75 with a rear drum brake had an 18" wheel, the one with disk brake had a 17" wheel.

mine have a disk brake and i know that the speedo is faulty and that`s why i thought i d`ont have the right size of rim & tire.
excuse my english. and tanks for the reply.

Your speedo may not be the original and maybe the one from a 1986 18"
Check the download section for Roy's speed calculator.

Bert

thank you Crazy Frog, i checked the speed calculator and did a test and everything seems to be ok.