piston rings on a 12hp Briggs and Stratton

[sean'sengines]

Hey!
Can any of you give me a step by step diagram (preferably with pics) to go by as I rebuild my 12hp I/C Briggs engine? It's off of an '88 Bolens ST120, and it needs new rings. I have the engine out and it's sitting on the shop floor as we speak. I just have to crack the case and unbolt the piston from the crank right? Should I get a new rod bearing as well as rings?

Thanks! :smile:

 

[KennyV]

Why are you changing rings???
Have you looked at the cylinder? Is there any amount of ridge on the top of the cylinder, is the bore still round??
How are the valves?
Also how are the main bearings and rod bearing... There are a few things you should be looking at as you go through an engine... Depending on the condition of the used parts, the hours on the engine, and whatkind of performance you are going to expect from this when finished...
What gave you the idea that you needed rings? :smile:KennyV

 

[sean'sengines]

I'm changing the rings, because oil is seeping past, and this thing blows blue smoke out of the exhaust like nobody's business. I figured I needed new rings, and maybe a new rod bearing. The valves were reseated last fall.

 

[SeniorCitizen]

The valves were reseated last fall.

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The above statement makes it real easy to diagnose the real problem and why the engine needs rings

. My guess is the valves were seated with lapping compound. The blue smoke follows shortly, sometimes with as little as an hour of operation, when it was done by someone that hasn't been informed about lapping compound.

 

[sean'sengines]

Yes they were, and I reseated the valves cause I thought that might be something to do with the smoking, cause it had been doing it for a little bit before that. If you start it up now, it'll blow smoke within the first 25 seconds of operation.

 

[benski]

I wouldn't be shocked if it needs a new head gasket. Of course, this would be part of the whole overhaul. If it was me, I'd keep an eye out for another used motor for about $120.00 or so, and just change it out.:biggrin:

 

[themowerguy]

I wouldn't be shocked if it needs a new head gasket. Of course, this would be part of the whole overhaul. If it was me, I'd keep an eye out for another used motor for about $120.00 or so, and just change it out.:biggrin:

I would love to know where you would find that kind of deal! From my experience, a 12 - 13 hp Brigg's IC is going to start around $350.00 at the very least.

Regarding the original post, rings are certainly a possibility, but you will also want to check for a few other potential problems along the way. Namely, you will want to check both the piston and cylinder walls for damage and scoring. If the cylinder walls are damaged, then the cylinder will need to be bored out, which would likely require an oversized piston and rings be installed - if they are even available. If there is a single, sharp score mark on the cylinder, check to see if anything in the pan is damaged (cam, valve tappet, oil slinger, etc.) that may have allowed a metal shard to get trapped between the cylinder wall and the piston.

If the cylinder wall and piston both appear to be in good shape, and there are no other signs of damage, then I say go ahead with the ring set.