Small Engines (Lawn Mowers, etc.): Briggs 12.5 hp, blowby, needle valve

Question
mod 286707  type 0420 01. Engine won't start.  gas collects  in bottom of air
filter housing but gas does not appear to get into cyl.  engine will try to start
with starting fluid.   There is a lot of crankcase blow by into carb air filter
housing.  I have replaced the needle valve because I thought carb was
flooding but as I said above gas still  collects in bottom of air filter housing
when trying to start.  Engine does not smoke.  Plug has good spark.  Could
the blow by be the problem and what would cause that ?  Thank you.

Answer
your having a problem getting fuel into the cylinder.  You have proven this by spraying starting fluid into the carb.  It sounds like you have a valve problem.  The intake valve is not sucking fuel into the cylinder thus creating your blowby your describing.

You will need to service the Valves.  This needs to be done by a machine shop that has the proper tools.  Most small engine shops have these tools.