Small Engines (Lawn Mowers, etc.): Briggs and Stratton Engine Model, briggs and stratton, air leaks

Question
I have a Briggs and Stratton engine that came off of an old (approx. 15 yr old) MTD front tine rototiller.  I want to overhaul it but I dont know the model number and no longer have the tiller or paperwork that would tell me it's model number so that I can get an overhaul kit.  Is there anything on the engine that I could look for to tell me what the model number might be? I believe that it is a 5 HP engine.  Thank you for your time.  

Answer
The first two digits of the engine model number will be 13 if it is a 5 HP.

http://engines.myfaqcenter.com/Answer.aspx?p_faqid=19

Be careful how much money you spend on the old tiller engine.  Tiller engines operate in the harshest environment and tend to be really wore out after they have been used for several years.  Valve guides and a new piston are usually required on a tiller engine rebuild.  I have also had really wore out carbs that just would not operate correctly because the throttle shafts and carb bores had to much wear causng air leaks.

If you plan on using the engine for a long time on another machine you may be better off buying a complete new engine.

Let me know if this helps.
Eric