The first thing I would say is IF you decide to replace the engine, DO NOT try to change brands or models!!!!
This would cause you considerable problems in the mounting and the charging system as well as the throttle controls and more.
There is NOTHING wrong with a Briggs Intek engine, But if you are having the problems that you are talking about, it is usually from not changing the oil and the AIR filter often enough.
All engines MUST have their oil changed after only a couple of hors of use because you have to bet the dirt and grit out of it that is produced during break-in. If the engine is run for longer than about 2 hrs before the first oil change, you will usually damage the engine. I also recommend that you change the engine oil and the AIR filter after then next 5 hrs for the same reasons. This will make sure that the dirt and grit is completely removed from the engine.
Even thought owners manual calls for longer oil change intervals than what I am going to tell you, you will get nearly twice the life of an engine if you change the oil NO LESS than every 15 to 20 hrs of use. the same goes for the OIL filter and the AIR FILTER.
This should be true with almost ALL brands of engines as well.
In any case,
the next part of your question is about the piston clearance.
I usually do not like to have more than ..04' clearance.
If you are going to try to rebuild this engine, you should have the cylinder bored out (Both sides) and use an oversized piston and rings. If you continue to use the one that you have, the oil burring and piston and ring failure will return again.
Here is the COMPLETE service manual for your engine.
Here are instructions on how to get the link and manual
1. When you click on the link above., a new web page called 4shared will open.
2. When 4shared opens, scroll about half way down the page until you see a BLUE ‘Download Now' button on the left side.
3. Click on the BLUE ‘Download Now' button. Do not click on any GREEN buttons.
4. Clicking on the BLUE button will start a 20 second timer.
5. When the timer expires, a BLUE link that says ‘Download Now' will appear directly above the timer.
6. Click on the blue ‘Download Now' link above the timer to start the download.
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