lawn mower engine

A friend gave me a Sears self-propelled 6.0 HP lawn mower because he got tired of messing with it. It's not very old and the symptoms are:
When it's cold, it takes 3 or 4 pulls to start it. After it starts, it runs fine even until the tank runs out. If you turn it off after it runs for just a few minutes or much longer, then it will not start until the next day. I have another Sears that isn't self propelled, but the carbs were identical. I swapped carbs between the two and the symptoms are the same, that is, the trouble stayed with the self-propelled.
Any ideas?
thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Could be the ignition module or coil is going, when you turn off a motor it temporarily gets hotter probably triggering the module. Unless if it has points it could be the condenser , be sure it is clean and removing the shroud may temporarily help. Are fuel lines the same, routed away from heat and the carb has the right gasket to prevent vapor lock? Check for spark first when it wont start, if it has spark squirt fuel in the carb.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yeah, it probably isn't the carburetor.
Maybe it is the loose nut behind the handle...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Loss of compression? Burned exhaust valve, worn rings?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.