Four inches is a lot to raise the 230 without getting into real complex stuff such as different model shocks/tires, etc.
Here's a couple of easy things to try.
1. Rear shock adjustment. Adjust the rings on your rear shock to stiffen the rear shock. When you sit on the bike the shock will compress less and thus ride higher. This will affect handling and comfort,.
2. Tire tread. Anytime I put on a new rear tire, my bike sits higher than it did on my old worn-out tire. Seems odd, but if your new tire has 1/2 inch lugs and your old tire is worn, that translates directly to ride height.
3. Front-shock pre-load. On the 230, you can increase the front shock pre-load by putting some washers on top of the fork springs. Make sure they're stainless washers so you don't get corrision in your shock oil. This can have an effect on your shock's handling. On my old 230 it improved the feel of the shock a lot.
4. Tall seat foam. You can get it here on CRF's only at:
http://www.crfsonly.com/catalog/product ... ts_id/1941.
Generally a tall seat foam give you about an inch.
5. Check what others have done. 2 folks that have posted a lot on the 230 are Mike Coe (
www.coeshow.com) and Rick Ramsey (
http://www.rickramsey.net/CRF230F.htm).
6. Use the search function on this site.
7. If this isn't enough, I think you're going to have to consider other more expensive options such as 250r front forks, swing arm and wheels.