Small Engines (Lawn Mowers, etc.): Engine problem after valve replacement, head valve engine, overhead valve engine

Question
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Followup To
Question -
Eric,  thank you so much for providing your expertise.
I have a 13.5 HP B@S single cylinder lawn tractor engine. During normal operation the exhaust valve got stuck in the open position but with a gentle push by hand it moved again freely. Still, I had a nearby shop replace the valve/seals etc. and put the engine back together except for mounting the carborator, which I did. The engine won't start now. Upon cranking with the starter motor the spark plug stays bone dry, no ignition takes place (the spark plug fires though), but blue smoke (air/fuel ?) comes out of the air intake in nice big puffs in sync with the engine rotating. Any hint as to who goofed up and how the situation could be remedeed would be greately appreciated.
Answer -
Do you have an over head valve engine?

Did anyone set the valve gap?

Let me know.
Eric


Eric,

no, it is not an overhead valve engine. Both valve stems lie parallel to the cylinder and are actuated from inside the crank case. By the way, the engine is a short-block-rebuild with the model number scratched into it and barely readable, but it looks like
284707-1036R8
According to the receipt from the machineshop they did the following when replacing the exhaust valve :
1) removed frozen valve guide
2) installed new valve guide and reamed to specs
3) replaced exhaust valve
4) cut valve seats
5) refaced intake valve
6) reassembled cyclinder head

Nothing is being said about resetting the valve gap. Could I have done something wrong when remounting/connecting the carburator ?

Cheers  .....  Zig

Answer
I would think they would have gapped the valves but I would check for sure.  You will have to remove the carburetor to gain access to the valve breather.  Remove the valve breather and you should see the valve stems and tappets.  Rotate the engine to Top Dead Center (TDC) where the piston is at the top of the cylinder.  The intake vlave clearance should be .005-.007 and the exhaust should be .009-.011 of an inch.

Newer manuals tell you to rotate the piston 1/4 inch past TDC to check the clearance but either method will work, TDC or 1/4 past TDC.

Let me know what the valve gap is.
Eric