i just got a 85 230 quadsport it runs smokes alot so i tore it apart to replace rings and maybe piston and found the topend is a 250
how can i tell what top end i have? is there markings somewhere?
the piston in it measured at 2.680 which is about 68mm

 

what years and or model 250 came in four stroke?

 

If it is from a 250 its probably a quad sport 250, I believe the quad runner heads were just different enough not to be able to interchange them.The quad sport 250's were made in 89-90, there almost the same machine as the 230, just with a punched up engine and enough body/suspension changes to make swapping the parts difficult.
There should be a stamping on the head somewhere that says 246cc if it is a lt250s head. The piston should measure out at 68.5 mm (or 69 and 69.5 mm for the factory oversize pistons). The engine's (whole) are similar enough to interchange with just some minor modifications, shimming, and electric's swapping. I have heard of people swapping heads but I don't know the spcifics, from what I understand Suzuki also changed the crank and rod to have a different stroak, as well as enlarging the piston. I'm not sure how to make the swap work.
If it is a 250 head the best bet for a rebuild is finding a 230 head and using it instead. Putting the correct parts on the bike will make things alot easier to fix now and diagnosis any problems in the future.
This is unless someone did swap the whole engine, the lowers do look alike. In this case you will have to take the number on the cases off and have it decoded to find out what year it is from. It's probably best to double check it anyway.
When you do this, this link will help:

suzuki engine and frame numbers 1971-94

 

thanks alot
turns out the whole motor is a 89-90 250s

 

just wondering, is your seat straight or t-shaped, maybe the whole bike is a 250s

 

the frame says lt230s

i have another 230s and the bottom end looks the same if it wasnt for the numbers i would never known