Mep 831A load issues

[grywitt]

Okay so the top ring was stuck in place. There are some scratches in the piston above where it (the gap) was stuck. I ordered a bore measuring tool. I thought for a minute that the timing was off because my dots didn't come together but with a little more turning they matched up. Ha ha.

Is a top ring stuck in place enough to cause the issue I've been having? I would like it if I could hone the cylinder and put it back together. I'll check the bad spots as well as diameter when I get the bore gauge. It wasn't that hard to free up the ring but it was definitely stuck at the end and only one end. The other end next to the stuck spot was free.

Like i said before I'm outside my expertise so advice is welcome and wanted. The rings actually seem to be in good shape to but I guess the smart thing to do is put new ones? I already tried to put a feeler gauge between the ring and the piston and it wouldn't go. It was .006 so bigger than the TM called minimum.

That same discoloration I saw on my rocker arms is on the crankshaft next to the rod rod bearing. Probably surface as well buy maybe that's where the explosion was leaking through. It is below where the piston was stuck. The oil was pitch black again. (No surprise)

This really is an awesome and fairly simple little engine i can see why it's liked so much. I'm excited to have this one running right. I'll probably never get rid of it.

 

[2Pbfeet]

Okay so the top ring was stuck in place. There are some scratches in the piston above where it (the gap) was stuck. I ordered a bore measuring tool. I thought for a minute that the timing was off because my dots didn't come together but with a little more turning they matched up. Ha ha.

Is a top ring stuck in place enough to cause the issue I've been having? I would like it if I could hone the cylinder and put it back together. I'll check the bad spots as well as diameter when I get the bore gauge. It wasn't that hard to free up the ring but it was definitely stuck at the end and only one end. The other end next to the stuck spot was free.

Like i said before I'm outside my expertise so advice is welcome and wanted. The rings actually seem to be in good shape to but I guess the smart thing to do is put new ones? I already tried to put a feeler gauge between the ring and the piston and it wouldn't go. It was .006 so bigger than the TM called minimum.

That same discoloration I saw on my rocker arms is on the crankshaft next to the rod rod bearing. Probably surface as well buy maybe that's where the explosion was leaking through. It is below where the piston was stuck. The oil was pitch black again. (No surprise)

This really is an awesome and fairly simple little engine i can see why it's liked so much. I'm excited to have this one running right. I'll probably never get rid of it.

Ok, not a ring expert here, so I will pass on whether one being stuck is enough.

However, I was taught always to have the gaps in the compression rings 180 degrees apart. Having both gaps aligned might be more than enough (I think) to explain your issue. The oil scraper ring should be +/- 90 from the lower compression/oil mist ring. I'm not finding Yanmar rebuild instructions for the rings, so please don't take that as per the manual.

Given the loss of cross hatching in the blackened area, I would not have any of the ring gaps in your blackened area if the ID passes muster.

All the best, 2PbFeet

 

[grywitt]

Correct me if I'm wrong. The carbon and smoke are from over fueling. So rings not holding proper compression mean each explosion isn't giving the expected power so it's sending more fuel to compensate. Hence over fueling?

I can at least see logic in that. I did find a guy around here that can to the honing and or boring for me. I'm in a terrible area for getting some things done. So either way I know where I'm getting the cylinder walls done. Now I just need to see if I need new rings or oversized piston and rings. Larger piston means more power right? Heck Ill be putting out 3.1kw.

I don't know engines enough to be sure I've found the issue but missing cross hatch and one end of a ring stuck sure seem possible. It was running pretty good and just not giving enough power.

 

[2Pbfeet]

Correct me if I'm wrong. The carbon and smoke are from over fueling. So rings not holding proper compression mean each explosion isn't giving the expected power so it's sending more fuel to compensate. Hence over fueling?

I can at least see logic in that. I did find a guy around here that can to the honing and or boring for me. I'm in a terrible area for getting some things done. So either way I know where I'm getting the cylinder walls done. Now I just need to see if I need new rings or oversized piston and rings. Larger piston means more power right? Heck Ill be putting out 3.1kw.

I don't know engines enough to be sure I've found the issue but missing cross hatch and one end of a ring stuck sure seem possible. It was running pretty good and just not giving enough power.

Yes, I think that bad ring alignment would lower compression, causing lower HP, causing the governor to call for more fuel, overfueling, smoke in the exhaust and excess soot in the oil. I have the hope that the black section isn't actually worn, it just has carbon deposits on it that could be honed off. As an explanation, I like that it might be this one item from the factory that caused the engine never to run well, and explains all of the observed issues.

0.5mm oversize isn't going to get you much extra HP, and as this is a generator with an electrically limited inverter output, I rather doubt that you would see any change from normal, though I hope the genset will run as designed. (And therefore better than it has been.)

Good luck- you've done a lot of work on this set; I think it owes you a debt for all of the TLC.

All the best, 2PbFeet