Small Engines (Lawn Mowers, etc.): low compression, will not start., coleman generator, valve clearance

Question
i have a coleman generator, with a tecumseh 10 h.p. model hm100, 159232k. it has about 100 hr. it was running good, shut off to change oil. then it would not start. i removed the head and found the exaust valve was not closing completly, it has no gap. the valve and seat look ok. what do i do next, before opening the motor case ?

Answer
Refer to the link below on checking the valve clearance.  Page 85 tells how to check and adjust the valves.  While a grinder is nice, often times a flat file works well to "grind" the valve stem to the correct clearance.  

When checking the clearance make sure the tappets, the parts that move the valves, are fully pushed down and not sticking inside their guides.

http://www.cpdonline.com/692509.pdf

Let me know if the link helps.
Eric