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Smokey 15.5 HP OHV Briggs


GerryC's Avatar
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03-30-17, 07:21 AM   #1  
Smokey 15.5 HP OHV Briggs

I've an old 15.5 Briggs & Stratton that became very smokey last Summer.
I changed the head gasket - old one was fine but changed to rule it out.
The breather is filling with oil. I emptied it out & runs ok until engine put under load & then smokes up again. I put another 2nd hand breather in - exact same thing happens.
I was assuming the piston rings are gone and the oil is coming into the combustion chamber through here & oil in the breather is a symptom rather than a cause of the problem. But looking at the chamber there is some slight scoring but not much. There is is also some slight scoring at roughly 45 degrees which makes me think it may of been honed before, its a 2nd hand mower.
I'm a newbie at this so only guessing.
Any suggestions what else to check.
Is it work stripping down to fit new piston rings & honed?
I was thinking maybe buying a 2nd hand engine & replacing this one.

 
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03-30-17, 07:55 AM   #2  
Check the oil to nake sure it is not over full and smells like gas which would indicate the float in the carb or the needle seat is failing. Have a good one. Geo














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03-31-17, 03:01 AM   #3  
The oil level was on the low side when I checked it, I assume from burning off.
Would a carb problem cause the breather to fill up with oil?
I've posted a crude video of the chamber. I don't think the scoring is that bad but I'm no expert by any means.
Here's the link: https://youtu.be/Eov-6DMG8kQ

 
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03-31-17, 09:53 PM   #4  
It says it's a private video.

Was the oil thin?


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04-01-17, 02:41 AM   #5  
Apologies, I've changed the video settings to public.
To be honest, I didn't notice the oil been thinner than normal but I didn't consider it as a potential problem. Same goes for gas smell, I didn't notice it but didn't check for it either. I used google & came up with the head gasket as a common failure but it wasn't this. I noticed the oil in the breather and cleaned it out & when it refilled I changed it for another 2nd hand one & same thing happened. Do you think this points to the carb problem Geo mentioned?

 
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04-01-17, 06:35 AM   #6  
That does look like cross hatch from honing however, there is also vertical scoring it looks like that should not be there. Check compression or leak down test.
It could be that it has ingested some grit at one point, or had been re ringed and not broke in properly.


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04-01-17, 09:36 PM   #7  
The cylinder looks decent but the vertical marks are slightly concerning, like maybe it was run too low on oil. I don't see scoring and it looks like probably original crosshatch from the original cylinder honing unless someone did a very exact job of honing the cylinder (doubtful). Can you shine a strong light down the side of the piston while trying to shove the piston to the side and be able to see the ring end gap on the top ring? If it's a large gap, I'd say you probably need rings.


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04-07-17, 05:49 AM   #8  
I took out the piston, here's a video of the rings.
Can I get an expert opinion on the ring wear state.
On that, the piston came out pretty easily, is that an indication that the rings are worn?
https://youtu.be/_pXToMEhO1c


Last edited by GerryC; 04-07-17 at 07:42 AM.
 
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04-07-17, 11:39 AM   #9  
The cylinder is more important to look at than the piston, or the rings ON the piston.
You can take the rings off the piston, put them in the cylinder and measure the end gap.
Also does the cylinder have any ridge at the top of it?


Just needs a bigger hammer
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04-08-17, 09:06 AM   #10  
The ring measurements were worst 0.02 inch, & other 2 are 0.018.
I assume this means the rings are Okay. Fun now getting the piston back on!
I'm not sure where you mean with the ridge. Only thing is the marks on the 1st video.

 
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