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Sep 13, 2019, 09:27 AM
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Deep cleaning really old abused engines


An old friend gave me 2 OS .61 FSR's. Both ringed. One is moderately clean on the outside, and may have been put away with after run oil, but not sealed. The other clearly was just put to the side after a crash - dirt/sand still caked on it. Maybe has been around 25 yrs they have sat. Both are solidly frozen - but I haven't tried to get more than a bit of a rock on the prop, to avoid any grit damage. I started to disassemble the worst one. The front and back cases, and head, came apart easily. So did the piston and the sleeve. But now I have to fight the goo. Rod is very glued to the wrist pin, crank is solidly frozen to the bearings and will not turn, thrust washer does not budge with my gear puller. I have sprayed liberally with "PB Blaster", and just now with crab cleaner. Con rod now moves on the wrist pin, but is still really "gooey". Before I start applying heat, looking for suggestion on a chemical or soak to dissolve out the goo. Carb barrel is in the same state on both, frozen solid - did I mention they both have Supertigre carbs?
They may be beyond saving, but I'd like to give it a go.

I'm familiar with the crock pot/antifreeze method, but am shying away from that due to possible discoloration of the aluminum. No ultrasonic cleaner yet, but could see what my local Harbor Freight has...any suggestions as to a "dip" and process to use?
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Sep 13, 2019, 11:11 AM
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Glow fuel works well to free things up, and then there is some oil inside so it not squeaky. I use carb cleaner or acetone for nasty ones, but fuel is fine. Use a lot, and drain it to get the dirt and dust out. I often use the Totally Awesome concentrated cleaner on the outside if the motor is too grungy to hold.
Sep 13, 2019, 12:29 PM
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I suggest you reconsider your reluctance to use heat... heat typically loosens/liquifies castor oil goo and is a comparatively gentle treatment.

Michael in Ontario, Canada
Sep 13, 2019, 03:11 PM
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Progress - lots of carb cleaner, and the con rod/wrist pin got very loose. Even though I got the c-clips out, and used my heat gun on the piston, no way will the wrist pin come out. Took the heat gun to the thrust washer, and it did pop off. Hmmm...crankshaft has a slot for a key, but there was a tapered compression cone covering it, with no corresponding slot for the other side of the key. So even if I dropped it somewhere, there seems to be no point to it.
Lots more carb cleaner, and put a big prop on it, and got the crank out. The front bearing seems to run very smooth! The rear is kind of rough, but very hard to tell if it is rust, or dried oil. Guess it is time to heat up the case and pop them out.....
There may be life in this very old boy yet. It will hinge on whether I can get the carb functional or not. But if I need a carb and a bearing set, then might as well start looking for a different engine.
Sep 13, 2019, 03:17 PM
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Gary Cee's Avatar
Heat is the strongest tool in the bunch
Sep 13, 2019, 03:21 PM
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Rinse out the bearings and they will likely be fine unless they are obviously rusted, not just stained. I take out the rubber and plastic stuff off the carb, and pull out the locating screw for the barrel. A soaking for a while, and turning the barrel clockwise with the arm so it doesn't loosen. Of course don't break it. If that doesn't work, and it normally does, then a heat gun on the carb will get it for sure. I have a couple motors where the carb seizes every time it is stored for more than a month.
Sep 16, 2019, 11:51 PM
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As Aspeed said, glow fuel is an excellent solvent for old glow engines. It’s good advice from someone that knows his way around model engines. I’ve freed up a few myself using only fuel. Sometimes it needs to soak overnight but it works.
Sep 17, 2019, 10:24 AM
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earlwb's Avatar
I would add that with lapped piston engines, especially the well worn well used engines to not do anything to the cylinder and piston. Just leave those parts alone. You really want to leave any varnish accumulation alone on them. As that may be the only thing giving them any compression.

With well used ringed engines, I am reluctant to clean the cylinder and piston too. The varnish may be helping on them as well. About the only thing I do is clean the piston ring groove, if I replace the piston ring. I know some guys like to hone or scour the cylinder sleeve with extra fine abrasives. But I do not like doing that. I have seen a lot of folks ruin cylinders by honing them or scouring them with extra fine abrasives before. The precision piston to cylinder fit is amazingly precise and it is very easy to loosen it up too much.

if you had access to multiple sizes of pistons, the honing a cylinder may be fine. You can choose from different pistons to get that precision piston fit back. The model engine manufacturers usually had a person in the production line that sat at a table with a large set of bins holding different size pistons. That person would choose the piston with the best fit for every cylinder. But we can't do that ourselves at home. Unless you have one heck of a workshop at home.


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