I'm reading all these posts about taking blackplates off and checking this and that for rust... My question is, what do you do when you take that backplate off and there's rust????

Clean it and replace the bearings.

Haven't seen this in any of my engines yet, but what's best to clean with????

The bearings cannot be cleaned but have to be replaced

The rust will wipe off the aluminum.

The crankshaft can be wiped off

The people that clean the rust from the crankshaft protect the bearing areas before cleaning. Which may involve sand paper or steel wool. I perfer to just wipe off with a rag and solvent.

Be sure and rinse everything well before assembly starts to remove the abrasive rust.

Coach,

The home I just moved out of is listed as being in Cusseta. I'm only a few minutes from you now, so we could look at your engine(s) just about any time you wanted.

I normally flush out the engine good with something like denatured alcohol followed up with WD-40 (WD-40 helps to remove residual moisture besides oiling stuff). Then I rotate the crank feeling for roughness or a slight rolling noise (like dry ball bearings rolling on the table noise), if you have a bearing problem, it is time to replace them.
Then if I plan on storing the engine, I use a better long lasting oil like automatic transmission fliud or something to oil the engine with.
Old castor oil tends to get dark after a long time and turn a brownish red like color, one should not confuse it with rust though.
It is common to see some rust spots on the crankshaft, that isn't a problem.  I sorta like to find a old engine, when I buy one, stuck or frozen with castor oil in it, as the castor oil tends to really protect the insides well. it isn't difficult to clean up the engine and have it running again.

Earlwb, great post on the subject. So many write off engines that come back to life simply by letting fuel soak in a little to free up some castor residue, and running a tank through the engine gets it back into service again for years. Rust on hardened steel cranks never bothered me in the least. Bearings are also hardened steel and superficial rust or castor stains can simply be ignored. When the bearing feels loose, makes noise, or leaks after I run it, then it's time for that bearing to be replaced. I always run them first.

Keep in mind that methanol itself is considered to be corrosive.

Then you have nitromethane that tends to leave nitric acid.

You are going to have rust from this sooner or later.

If you use WD40 to clean it, be sure to remove all the WD40 and replace it with a good oil. WD40 is NOT a lubricant, it is a water displacement fluid. If you use just WD40, it displaces the rust and leaves a nice abrasive bunch of goop in the engine which will do a nice job of wearing out the bearing at a faster than normal rate and scour the sleeve and piston. IMHO you are better off to NEVER get WD40 inside an engine.

Methanol tends to attract moisture, its in its nature, but methanol isn't corrosive in itself, it is the moisture it absorbs that leads to corrosion. Nitromethane when burned or combusted in the engines gives off a nitric acid residue. I remember reading about some folks in Australia discovering that their nitromethane they were using was contaminated with some nitric acid right out of the container too.
The glow fuel has some other combustion byproducts as residue that can lead to corrosion too. Some of the synthetic oils they use in glow fuels tend to attract moisture as well.
Castor oil tends to have a tenacious film strength and sticks to metal surfaces really well. it'll displace other oils for the most part to get next to the metal surfaces. But over a long time Castor oil tends to dry out some and get more stiff or harder and more varnish like.

So when you flush out the engine you are attempting to remove as much of the combustion byproducts and fuel residue from the insides of the engine. After flushing it out good to remove the residues then you reoil it to protect the metal surfaces. The moisture combined with acids and residue on the ferrous metal parts leads to corrosion occurring.
Here is a cool article on what causes rust: http://www.corrosion-doctors.org/Exp...-chemistry.htm

some interesting stuff on ball bearings corrosion and pitting: http://findarticles.com/p/articles/m.../ai_n21440477/

Though in 55 yrs or so playing with model engines, I have never seen any evidence of aluminum corrosion from methanol?</p>

I can agree with you, I have never seen aluminum corrosion in our model glow engines yet and I have been at it for many years too.
I wonder how they came up with that. Pure Methanol is really close to being neutral at a PH of 7.0 but not quite.
But PH levels are measured for aqueous solutions (water mixed in it) so a PH doesn't measure out for methanol in its more or less pure state.
Now granted it does start to become slightly acidic as the water percentage increases, but you are talking about something like 12% methanol to 88% water then. But heck with enough water the ferrous metal parts start corroding without methanol anyway.
Maybe someone who is real good at chemistry will chime in and explain it.

A trick I learned about not long ago from another model forum for cleaning rust from steel parts is to immerse them in white vinegar and let it sit for a day or so. It works a charm but I wouldn't do it with bearings. I've never actually seen a rusted bearing but I've felt some that I thought might be rusted, either totally seized or extremely lumpy. All of them only had hardened castor in the races and, after cleaning, were as smooth as silk. I've cleaned bearings by soaking in warm water and dish washing liquid, acetone and in a small ultrasonic cleaner with a little CLR (Oil and Grease Remover) added.

Corrosion? THIS is corrosion . Luckily I had a spare crankcase .

Yeah I can agree, that is corrosion?  But it wasn't caused by methanol was it?


In my studies of it, it isn't really that the bearings or races get rusted so much as micro-pitting that is occuring.
The steel used is actually an alloy of a number of different elements, such as iron, carbon, chromium, nickle, silicon, phosphorus, et cetera.
The micro-pitting corrosion occurs in the tiny crystals on the surface of the races and balls where the balls make contact with the races where the different elements setup a galvanic corrosion of different elements in the steel alloy resulting in micro-pits forming. Moisture, or water combined with any fuel residues like nitric acid help promote this corrosion. Once you get micro-pits occurring then the flaws start getting worse as it cascades towards failure up through macro-pitting and so on.
There used to be some cool articles on the internet about it, but it seems everyone wants you to pay for it now.
I did run across this one in PDF format though: http://www.nrel.gov/wind/pdfs/46572.pdf

We have CLR here too.

Except ours is for lime and rust scale not oil and grease.

I think it's the same product that we have here. I had to look it up after mentioned it though.

The original CLR stood for Calcium Lime and Rust (in a green bottle I think) but the later one in a black bottle is the one to use. And I'd hope the engine in my photo had never seen methanol because it's a diesel . That corrosion would have been purely galvanic corrosion between the iron in the bearings and screws and the magnesium crankcase. Strangely, the spare crankcase I had was given to me after it'd been under water in the '74 Queensland floods (like what's just been all over the news lately) and I'd just thrown it in a drawer for all those years yet it was perfect, including the bearings.

Good, vacuum degassed steels used for bearings won't have the microstructures you speak of. What is far more common is micro-welding of the microscopic high spots in the bearing races and balls. This causes small tears in the surfaces as they are pulled apart during rotation. Over time, these tears get larger and larger and the bearing gest noisy. With the marginal lubes used in a lot of fuels, this is now the "normal" wear mode for bearings. Adding some castor to the lube mix reduces this quite a bit.

Evapo-Rust, Evapo-Rust, Evapo-Rust!

It will not fix a rusted bearing.

I agree, rust will case the bearing to fail eventually even if it is cleaned off. I tmay feel smoother but the damage caused by the rust will lead to an early grave for the bearings and possibly the engine depending on how it fails.

I was not implying it will fix a rusted bearing.

It will however remove rust from any ferrous metal that you can re-use.

Most any bearing failure I've seen or heard about was the riveted bearing retainers failing.
Usually trashing the piston & liner at the minimum.

Bearings are cheap insurance and the ones with the plastic/composite type ball retainers work best for Me.

If there is any doubt at all I replace them.
Jeff

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