I am getting ready to order a new rear tire, as my current one has worn down. I formerly asked about sizing/fit on going larger, and got a lot of great info. My new question is what is the equivalent (100/100, 110/100??) of the factory Dunlop 603 that is on my bike. It is currently a 4.60-18 63P

 

110/100-18 is about the same.

 

Dunlop suggests a 90/90-21 Front and 120/90-18 Rear. Personally, I have a 3.00-21 Front and 4.50-18 Rear, both are Kenda K270.

 

You are correct. I went to the dunlop website before I bought my new tire and I selected my bike, and they gave me the same info. They say the D606 is the replacement for the D603. The new factory replacement is D605 only from a dealer at a nice $186. I got my D606 from dennis kirk for $77 and that included shipping.

dunlopmotorcycle.com Click on fitment guide, select Kawasaki, then the 06-10 klx250s and all the info pops up.