let me second the "replace the plug" suggestion - I've seen this
happen several times, and plugs are cheap. if you have compression
and spark, some ether (starting fluid) sprayed into the intake as you
crank should make it fire pretty much no matter what else is wrong.
No idea if it'll be any help, but the first thing I would try is replace
the plug. Mine deteriorated to where it would not spark under
compression. It looked fine and sparked nicely in open air, but not in
the cylinder. Cheap fix if your luck's running good lately. 
Funniest one was one _cold_ day it wouldn't run more than 3-4 seconds.
After practically disassembling and reassembling the engine, I found
water had frozen in a low part of the exhaust system. First time I had
an engine failure from a frozen up exhaust. Solved the problem with a
hair dryer and thereafter, making sure to rev the engine to expell the
water before shutting down.
Bill
www.wbnoble.com
to contact me, do not reply to this message,
instead correct this address and use it
will iam_ b_ No ble at msn daught com
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