suicune apears at the port in vermillon city and later at route 14 and at last go to route 25 and catch suicune
you see suicune on the route to mohogany town you have to use cut to get to it please recommend (if it helps) =]
go by lavandar town
mahogany town is in the south of the lake of rage east of blackthorn town and in the east of ecruteak city
Suicune is on Route 25.
suicune is on the right side somewhere on route 14. after encountering suicune there, if you met misty at the end of route 25, you'll find suicune there and you can battle it.
Suicune is probably not on route 25 if you met him everywhere else because you haven't caught Entei and Raikou. If you caught them and Suicune still isn't there then look at the places Suicune was, then go back to route 25 WITH ENTIE AND RAIKU IN YOUR PARTY!
In the grass but Suicune moves a lot so you will not always find it there.
it is not on route 18
first, you find him in cianwood city, not mahogany town. second, the next time you see it is when you first arrive in kanto from the s.s. aqua. after that it'll be on route 14 where it runs away for the last time. you can catch it at the end of route 25 after the encounter on route 14.
In the grass.
To get Suicune first you will see it north of Cianwood City, then you will see it outside the entrance to Mt.Mortar in Route 42. After that you will see it in Vermillion City, then route 14. Only after Misty has returned to her gym you will fight Suicune on Route 25 outside of Bill's House.
In Pokemon HeartGold and SoulSilver you can catch Suicune in Route 25 however if you have knocked it out during battle then you can defeat Lance and then Suicune can be found for future battles in the Burned Tower however Suicune cannot be found in Route 25 until you have released it from the Burned Tower and then you have encountered it in Cianwood City, in Route 42 which is the outside entrance of Mt. Mortar, in Vermilion City and then in Route 14.