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One way to define UGLY


MPH

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Pulled the Onan off the ditchwitch today and took the heads off, what a shame, NO ring rid, but rusted and pitted really bad. Not sure if the pits are into the cyl wall yet or not. Anyone have great stories of success of derusting an engine? Kinda like to save it as my bro tells me the NH is a 25hp model. Back of the bench project best I figure, just keep soaking it one side at a time..MPH

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Marty, Looks like you better order the 1-gallon size of Kroil for this job (LOL)! May think about looking into oversize pistons from NAPA? Tom(PK)
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Hellooo Marty, What happened to the rust removal solution I sent to you? Clean off all the dirt, old oil (power wash if you can)etc. Soak the cylinder in solution. Rust will be dissolved out even in the pits.
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Crossed my mind to use that Woody, Though I was saving it for my 725. Should I just mix up a portion of it and fill the cyl hole up??Would it soak down around the rings?? Thanks..MPH
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Marty, Once you get all the grease and grime off the engine I would turn that engine upside down into the solution. As the rust is dissolved it will penetrate deeper all the way to the rings. Don't forget to keep the solution at or above 70 degrees. That block has a lot of mass which will cool off the solution. You will most likely have to add heat in some way. If grease is on the part the water based solution can't get to the rust.
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Try a very fine cylinder hone and a 3/8" drill and see where that gets you. If rust isn't too bad it shouldn't harm the bore. By looking at the brown matter on the bench, I assume that was water that came out of the cylinder and maybe the rust didn't build up that bad.
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Woody, I divided the wt of the package to equal 1 pt of solution, washed one cyl out real good with hot soupy water, rinsed real good, blew it dry and filled it to the brim. Its rt at 70 in the shop, hmmm wonder if I have an old engine block heater around.. Bob, can't really use my hine while the pistons are in, I don't want to drive them through the rust. Your rt on the water that ran out when I broke the head lose, if you look at the cardboard you can see the wet area from the flood. In the bottom on the cyl there was about 1/4inch of rust matter, under it the walls look nice, the worst rust/pitting buildup is on the top of the hole, don't claim to totally understand that, condensation from temp change for unknown years maybe. The motor oil was pretty clean lookin and the total lack of any ring ridge has me thinking the motor hasn't done much work.. MPH
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Woody, that rust remover is pretty impressive. I used a block heater to keep it warmed good for about an hour last nite while I did some other stuff, as I couldn't just leave it plugged in, threw half dozen head bolt nuts in the hole that I had to force the socket onto over the rust, looked at the this am and not bad, heated it for about half an hour and the nuts looked good so I spooned the cyl out, WOW, the rust buildup was gone and the pitting don't look tooooo bad. Put some penatrating oil in the oil to soak while I go to Whitehorse for the next few days. I took some pics, but my 69 dollar camera doesn't do flash shots good, the nuts didn't come out at all, heres one of the cyl hole...Thanks....MPH

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