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cleaning rusty crank - 8/9/2011 9:25 PM   
flybyjohn


 

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From: Helena, MT, USA
Status: offline 		I aquired an older extra 300s aerobatic today for $60.00 with an os surpass 91fs on the nose. I turned the engine over by hand against my better judgement and noticed no compression and the bearings feel jerky. I assume I will have to replace the bearings but was wondering how to clean any rust off of the crank shaft. I was planning to hot antifreeze dip the engine components but Is there any special chemicals for a rusty crank or just go to it with a brass bristle brush. Antifreeze has never worked well on rust for me, just the caster residue. So what's the cleaning proccess for a rusty crank?

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RE: cleaning rusty crank - 8/9/2011 9:43 PM   
earlwb


 

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Status: offline 		I normally don't worry much about rust on the crankshaft all that much, unless it interferes with getting a bearing on or off.
I use some strips of  super fine 800 grit emory paper on the crank to get any crud or rust off that stops a bearing from going on OK Just enough sanding  to allow the bearing to go on.  But one can use Naval Jelly to good effect.  Using a wire brush is useful too, especially if you get some wire brushes for your dremel tool.   For old castor oil that has aged and congealed, some Dawn Power Dissolver works well. I spray on some and let it sit for a few minutes and use a tooth brush to scrub it with. Reapply as needed. Now removing the rust still leaves the pits though. But in any case I only remove enough crud to let me replace the bearings, etc. I see no reason to go all anal and get it to look like new. The rust will prevent that new look anyway. Plus the old castor prevents rust, so leaving a thin layer on the crankshaft doesn't hurt anything. Most of the time, instead of rust, you have old castor oil layers that have built up over time and congealed, so there isn't rust per se on the crankshaft.




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RE: cleaning rusty crank - 8/10/2011 12:53 AM   
flybyjohn


 

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Status: offline 		Thanks for the info. After I got the cowl off the engine looked quite clean. I borke it down and the all the bolts were extreamly hard to remove. There was a good build up of chalky black crud on the piston top and the exhaust valve. The piston ring feels sharp on the edges and the liner is smooth and scratch free. I could not get the bearings out even after putting it in the oven for 10 minutes. I put all the parts into the antifreeze pot and will see if baking the bearings a bit will allow them to come out. The other thing I could not get out was the cam shaft/gear. it is being held in by the opposite bearing. I got both lifters out and the crank out but the gear is still stuck in there. It wiggles around and turns but will not pull out with needle nose pliers. I do not want to damage it so next I will try and sqeeze harder with the needlenose with some black electrical tape on it.

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RE: cleaning rusty crank - 8/10/2011 2:53 AM   
earlwb


 

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Status: offline 		The oven actually doesn't work well, as it evenly heats up everything to the same temperature. What you want is for the bearings to be cooler than the heated up crankcase, thus the crankcase expands more than the bearings do. I would suggest a good heat gun like for heat shrink tubing or Monokote or a propane torch. With the bearings cool then heat up the crankcase on the outside and if you can't get the bearing to pop out, use a 1/4 brass rod with a flattened out edge on it, and a hammer to gingerly tap the bearing out. The crankcase is heated up to around 250 degrees, too hot to hold in bare hands so use leather gloves. The idea is to quickly heat up the crankcase and knock the bearing out before it heats up too. Old oil and crud can make the bearing stick, so you might have to use a brass rod to knock them out with.


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RE: cleaning rusty crank - 8/10/2011 3:42 AM   
blw



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Status: offline 		Earl, I've gone as high as 375 F as a last resort for a really stubborn bearing. I've always used wood dowels. Brass would be quicker.

Conversely, I had an engine with 25+ years of dried castor and the bearings popped right out the first time I heated the crankcase with the covering gun.

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RE: cleaning rusty crank - 8/10/2011 3:55 AM   
downunder



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Status: offline 		For cleaning rust off iron parts, put them in a jar filled with white vinegar and leave for a day or two.

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RE: cleaning rusty crank - 8/10/2011 1:12 PM   
flybyjohn


 

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Status: offline 		Thanks for all the replies. The engine parts cleaned up good. I still have not got the bearings out yet. I will try the heat gun and brass or wood dowel tonight. On all my two strokes, the bearings fell right out after being in the oven for 10 minutes.

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RE: cleaning rusty crank - 8/10/2011 1:49 PM   
kenh3497



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Status: offline 		The aluminum expands more that steel. Even if everything is the same temp the bearings SHOULD come out. Now with that said, getting the crankcase as hot and quickly as possiable is best. i use a propane torch. Put the crankcase in the antifreeze, bearings and all and get everything as clean as possiable. It sounds like you will be replacing them anyway. That should help with removal by getting all the old crud out of the way. The antifreeze won't hurt the bearings, so if they are bad it's because they were bad before you cooked the motor.

ken

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RE: cleaning rusty crank - 8/10/2011 2:58 PM   
wcmorrison



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Status: offline 		Probably need to replace the piston ring too.  Sounds like the old ring is stuck.  Putting the piston in the hot/warm anti freeze over night may loosen it up.  Otherwise, get a replacement.  If you replace it make sure the ring groove is cleaned out well.  So if you replace the bearings, you might as well replace the ring.

I have used jeweler's rouge and a buffing wheel to clean up crankshafts.  I would not use any emory cloth at all, the rouge is much finer and will not remove gobs of material to get the surface rust off. But otherwise, like others have said, unless the rust interferes, I would just leave it alone.

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RE: cleaning rusty crank - 8/10/2011 4:22 PM   
Kmot



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Status: offline 		Evapo-Rust works like magic on rust.

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RE: cleaning rusty crank - 8/10/2011 4:25 PM   
fizzwater2


 

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Status: online 		scotch-brite pads work to clean light rust off of parts, too.

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RE: cleaning rusty crank - 8/10/2011 6:41 PM   
proptop



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quote:

ORIGINAL: fizzwater2

scotch-brite pads work to clean light rust off of parts, too.




I've switched to the Dremel scotchbrite type scrubbing buff, instead of the wire wheels...eliminates the chance of involuntary accupuncture...

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RE: cleaning rusty crank - 8/10/2011 7:02 PM   
flybyjohn


 

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Status: offline 		I ended up just rubbing the crank a little with some fine steel wool and it cleaned up rather nicely. The jornals are a little discolored but the surfaces are pretty smooth. The ring came off easy and all the edges look/feel sharp. A tooth brush cleaned the ring grove out good after a soaking in the antifreeze. I'll stick the engine in the freezer for a while then hit the case with some heat and the bearings should come out then.

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RE: cleaning rusty crank - 8/11/2011 3:48 AM   
blw



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Status: offline 		It sounds like you are doing well.

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RE: cleaning rusty crank - 11/5/2011 6:05 AM   
Quikturn


 

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Status: offline 		Ditto on Evapo-Rust! It really works well.


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RE: cleaning rusty crank - 11/5/2011 2:16 PM   
iskandar taib


 

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Status: offline 		Ovens seem to work fine for me. The aluminum case expands more than the steel bearings do, so I put the case nose up on a cookie tray and wait till I hear the "thunk" of the rear bearing falling out. The front can then be removed with a dowel.

To reinstall the rear bearing, the case should again be heated in the oven. This time the bearing will be at room temperature so it'll be an even looser fit into the hot case. Use the shaft as an installation tool.

In any case, heating the case is especially necessary for racing and combat engines, where there is a strong interference fit between the case and the rear bearing.

Iskandar

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