Honda 5.5hp GCV160 possible valve or piston ring issue?

[arch252]

I have a Honda GCV160, GJAEA-3313087 mounted on a pressure washer. I picked it up in non-running condition with little history about it. When I got it there was an obvious major oil leak coming from the valve cover. This is the first engine like this I have worked on. I was quite surprised to find there was no head gasket and the case splits in an odd diagonal direction. I learned the hard way about keeping the valves in place before you remove the crankshaft. They slipped out and I had quite the time removing the crankshaft.

I removed the valve cover to expose the rockers and the plastic timing gear and timing belt. There was a significant amount of oil in the valve cover, far more than I have seen before and more than I expected to see, but not having worked on this type of engine before I didn't know if that was normal. I removed the valve keepers and springs. I removed the valve stem seal from the intake valve. There was not a stem seal on the exhaust valve. It was obvious that a lot of oil had been passing through the exhaust valve stem opening, there was burnt oil residue build up on the retainer side (valve cover side) of the exhaust valve stem opening.

It doesn't seem right to me that there should be that much oil passing by the piston and being pushed out through the exhaust valve. The burnt oil residue seemed to indicate to me that the oil was being pushed through at extremely high pressure by the piston, causing the oil to burn.

Based on this can anyone identify what the problem might be. Are the piston rings bad and allowing excessive oil to pass? The cylinder looked just fine, no scoring at all. There were no metal shavings or anything out of place in the crankcase. I don't see anything obvious.

If the rings are the culprit and I replace the rings, is it likely that any permanent damage has been done?

Has anyone run into this before? Needing some guidance. Thanks

Rick

 

[motoman]

Rick, I'm sure some Honda guys will respond to this. I have had engines which drew lots of raw oil thru the exh guide, enough to form a ring in the exhaust port. That engine (looking back) had excessive oil flow to the valve gear with no guide seals. This issue is interesting. While AC engines should benefit from oil flow (cooling) around the valve guides my Intek only has a misting and no more than 1-2 table spoons of oil sitting in the valve cover when I adjust. Also while I would think the intake guide normally would admit more oil to combustion than exhaust, the Intek exh guide has the seal , with none on the intake (I think).

Anyway , tell us what the "excess" you found is, tablespoon etc. Also if you are that far into the engine look further for a broken ring. I know you know you can not just replace rings without checking the cyl dims, and hone.:2cents:

 

[arch252]

Thanks for responding. I can't tell exactly how much oil was in the valve cover. It caught me off guard when I cracked the seal and most of it dumped on the table, I wasn't expecting anywhere near that much. Like you, I usually only see a tablespoon or so. After most of it ran onto the table and my shop rags, when I took it off completely there was still about 4 tablespoons left, about a 1/4 cup. They had obviously ran the engine like that for a least a little while because the oil was well set on the front of the pressure washer where it was running out of the valve cover.

I have always checked the cylinder dimensions before installing new pistons and rings but I have never honed a cylinder. If it is marked up or scored at all I don't mess with it. I haven't checked for a broken ring, but that's certainly easy to do so I'll check it out. I went ahead and ordered a piston and ring set but I want to know for sure what's causing the problem before I go much further.

 

[motoman]

There are ways to check the valve guide clearance. A small hole telescoping gauge is fairly cheap. I used one to measure the Intek valve guide clearance. They are kind of tricky to use so I took an average of 5 measurements. Then the od of the valve stem. Short of that there are methods done with a dial gauge set up over the guide. The valve is lifted (no spring) off its seat and a sideways measurement is taken, but those measurements are engine specific . Still short of that the same wiggling done by hand , but then it's judgement.

Taper and out of round of cyl. If you can borrow a 3 point bore gauge. Small (thousandths) cleanup with a power hone, not the glaze breaker type. Still waiting for our Honda gurus to help you.