I have a Murray 30" rear engine 12hp (28R606). I blew the motor. Had opportunity to acquire a 12.5hp (286707), however came without carburetor, muffler and starter. I was told that I could mount carb, muffler and starter from 12hp on the 12.5hp without issue. I found that I had to change the starter gear, starter working fine. Engine doesn't want to start. Sounds like it wants to. When I fiddle with Governor I can get it to start, but seems to run very rough and won't continue to run. Also seems to get pretty hot. Seems like a timing issue, but I have replaced the flywheel key and oil as precautionary. Please help.

Hi,
Could be a timing issue, but I doubt it. Carb will not necessarily work though I would think it would. My most probable guess is that it is an air leak caused by badly cleaned gasket surfaces. It is really important that all the old gasket(s) are removed. Air leaks cause your symptoms.
Peace,
Clarke

Hi,
Could be a timing issue, but I doubt it. Carb will not necessarily work though I would think it would. My most probable guess is that it is an air leak caused by badly cleaned gasket surfaces. It is really important that all the old gasket(s) are removed. Air leaks cause your symptoms.
Peace,
Clarke

I found that the Head Bolts were loose and Gasket in bad condition. I will replace and see what happens. That may be the air leak?