Disassembly may not be required. I never disassemble an engine unless it's broken. If it was ok when you last used it, you should not have to take it apart. Here's what I recently did for my 25 FSR, 25F ABC, and Saito 45, all of which had been sitting unused for 15 years.

First step is to see if it turns. Remove the glow plug (this is the extent of my "dissassembly"). If it's all gummed up, like mine was, put it in the oven at about 300 degrees for 10-15 minutes. This will loosen up the gummy stuff enough to turn it. If it turns before heating then just go to the next step.

When you take it out, put some some rubbing alcohol down the carb and into the exhaust port. Don't forget to use pot holders or mits, the sucker is still quite warm. The alcohol will loosen up the gummy stuff and allow it to turn. Don't forget to move the throttle arm some too. When you've turned it for a while, pour out the sludge and add some more alcohol. After a few rounds of this, the gummy stuff should be gone from the inside. Next step is to clean the outside. I found that the rubbing alcohol and a toothbrush work wonders for cleaning the outside. For really stubborn stuff, just let it sit in alcohol for a few minutes. Once you are finished, put it back in the oven for a few minutes to evaporate the alcohol, and then oil it up.

Total time, no more than about 30 minutes, and the only thing I took off the engine was the glow plug.