Stuck crank

The crank on my 81 cr430 seems to be stuck to the magnesium case due to oxidation from the dissimilar metals. Would anyone know of a product that would dissolve the oxidation?

Thanks!

I just acquired it. It sat for a very long time and the corrosion built up between the case and the crank.

There is very little clearence between the crank wheels and the crankcase. It doesnt take much moisture to corrode the magnesium and they stick. The ignition side crank bearing is exposed to the crankcase and usually needs replacement if there is crankcase corrosion. The crankcase and crankshaft usually cleans up well for reuse. If the barrel was on it the piston usually stops before TDC which is helpfull because it keeps the rod bearing out/above the corrosion. I would never try to get one freed up and run it without splitting the cases. I have salvaged quite a few with no problems. A crimped wire brush on a drill will clean the corrosion very well.

soak it with diesel. Dont be in ahurry, leave it for a week, keep putting more diesel on it or in it. maybe heat up the whole bottom end if you have to. I use a weber type barbecue when I heat up cases

I agree with SA63. I would use Kano Oil and a heat gun.

I use PB blaster, I've found nothing better or quicker working.

I second PB Blaster....also use automatic transmission fluid. Has excellent solvent properties

How about not worrying about getting it free. To dis assemble the engine or split the cases as it is often termed pressure is applied to the end of the crank by a device which attaches to the engine case. This is done from both sides, the first side is when the cases come apart and the locating pins can stick some. At least that is how I have been doing it. It (the crank-crank cavity) would have to be pretty corroded to have more resistance than the crankshaft bearing locations sliding on the inner race/races of the main bearings.

Husq fleet Do you paint or treat the surface after the crimped wire brush? And then if you do have you ever seen how well it lasted.

Sorry I don't know what chemical would dissolve the corrosion of magnesiun. Phosphoric acid is what one uses for the early stages of corrosion of steel but once you get a "bark" I don't know, I usually use a flame for that. It is the active ingredient in cola beverags and somehow works to pull calcium out of your bones when you dink cola products containing it.

Fran

Fran, I am in the process of splitting the case but am having a very difficult time of it. I was thinking if I was able to dissolve the corrosion then the cases would pull apart easier.

Well a simple internet search came up with this http://www.ehow.com/how_5863187_remove-corrosion-magnesium-aircraft-parts.html I guess it is chromic acid but you can't rinse it off if it doesn't work and I havn't studied what it would do the steel crankshaft.

The crank didn't even budge when removing the nuts on the primary gear or electric component? You could put the primary drive back together weld a bar onto a sprocket put in gear probably a high one and see if you could get it to wiggle. A few minutes of heat from an electric heat gun (not a hair dryer) should get enough expantion in the case that the bearings will move in the housing under normal circumstances.

I have a set of quite corroded cases which are otherwise good except the crank cavity but didn't take that engine apart. The (standard shift) ones I have taken apart havn't had issues in the crank cavity I might also mention that there is a steel insert (maybe cast in?)in the case where the crank bearing is and the crank end being steel could corrode as well. I would think the electric side would be the easiest to moove as the race is shorter than the two on the drive side and it would be up hill if the bike was on the kickstand. Obviously you can only force it so much or the threads you attach to will pull out.

Fran