Small Engines (Lawn Mowers, etc.): B&S 42A707 2238E1, briggs and stratton, dirt bikes

Question
My mower has been a great one and I want to keep it that way. I went out to mow yesterday and the only way it would run at its best was with the choke out about 1/3. If not it stumbled all over its self. Any Ideas would be great. Also I want to set the valves. What are the valve clearences suppose to be? And is there any online manual that would show me where everything is located, meaning the valves. I work on Atv's and dirt bikes a lot so im able to do the work, just need the info.

Thanks a lot
Dave

Answer
Carburetor is probably dirty causing the lean running condition.  Below is a good link from Briggs and Stratton.

http://faqs.custhelp.com/cgi-bin/faqs.cfg/php/enduser/std_adp.php?p_faqid=3441&p...

Eric