it is an 18" on front. i did that very early on, like maybe 2,000 miles on bike or less. mostly due to bangin over rocks down south in tn, nc.. with the 21 seemed to smack rim alot. don't have that problem with the 18.
it has a heavier feel for sure, kinda like a built in steering dampener. every now n then i will throw the 21 back on for heck of it and don't like it. steers very quick and feels like it will tuck front end.
guess i am just used to it. i really don't even know which tire is on front as i have tried so many. i would have to look but usually run dunlop or maxxis. i am sure from now on it will be a maxxis as i got a line on very good condition take offs from local racer for $15 each!
i have had many bikes over the years but that wraggly klr is the keeper. don't know what it is about that thing but it works for me.