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Tuesday 20 August 2024
Monday 17 June 2024
Unseizing a Ring Stuck in a Piston
I was rebuilding a Honda GX140 motor that is part of an industrial pressure washing system that I acquired for a mere $100. The engine had been sitting outside for ten years and was definitely seized. The spark plug was missing, so who knows how long rain had been collecting inside the cylinder.
I followed YouTube videos on how to unseize a motor by pouring in a voodoo concoction of half carburetor cleaner and half kerosene. The idea is to constantly soak the piston in the rust-fighting chemicals, jiggle the cylinder frequently, and work the crankshaft until the piston eventually frees up. This happens over a couple of days. The biggest danger is if frustration takes over. You can apply too much pressure and break or score the parts.
In my case, the piston freed up after a reasonable time - two days. There was a substantial ridge of rust at the top of the cylinder wall that took rust eater and some light scraping to remove.
Once the piston was out, the hard part began: the rings were frozen solid into the piston grooves. I started another days-long round of suggested fixes including soaking in the aforementioned chemicals, heating the piston with a heat gun, tapping the rings with a plastic hammer, spraying penetrating oil, and even boiling the piston for 20 minutes.
Hours passed without apparent progress. Then, as the lyric goes, "Just a little change, small to say the least"! Under heat, part of the ring lifted ever so slightly. At first, I assumed it was wishful thinking because the change was barely perceptible.
An hour or two later, something else happened: rusty liquid seeped from a tiny area of a ring. It wasn't even a whole drop but an encouraging clue that the constant spray of toxic products was getting into the right place. All of the tutorials tell you that you must have patience. The problem is, they don't tell you how much patience is required.
In my case, the bottom ring raised and came off first. I used a small pick to get into the gap and work it loose. Next was the top ring. It broke in several places because I was too eager to pull sections off instead of waiting for the penetrating oil.
The middle ring almost broke me. I kept thinking that for 50 bucks, I could abandon this nonsense and order a new part. But hope springs eternal even if the ring does not.
The final breakthrough was entirely unexpected. I was almost defeated and ready to hit the Order button for the part. But I went back out to the garage to give it one more college try. There seemed to be a subtle change in the ring, where I thought I might be able to get my pick into the gap. Risking stabbing by other hand, I applied more pick pressure than I had previously dared. At this point, if I ruined the piston, I was out nothing anyway, right?
Wow! Things moved!
In terms of a story, this was the climax. I knew everything would resolve itself fine from that point on. Sure enough, during the denouement, I picked and sprayed, heated and sprayed, and finally had several broken pieces of ring to my great satisfaction.
I shared this small joy with my wife who offered an unenthusiastic "congratulations". Her flat response didn't matter. I alone knew this was a major achievement. I had shown patience and persistence, and triumphed over years of rust and neglect.
Yes, the piston and the rings were unseized and the key parts were not damaged. What's more, I had saved myself 50 bucks with only a week's labour (and 40 dollars' worth of chemicals)!
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