Question: I have pulled the back plate from my engine and I can see rust on the back of the crankshaft and on the rear bearing. Is it OK to run the engine like this? If not, how can I remove the rust?

Answer: It is not a good idea to run the engine until the rust has been removed. The rust is very difficult to completely remove without disassembling the engine but you can do a reasonable job with Pacer After Run Oil and Pacer Degreaser. Commercial rust removers have been used but can cause problems with gaskets, O-Rings and aluminum so we do not recommend commercial rust removers unless you completely disassemble the engine.

Better Answer: Rust does two things, it erodes and pits the smooth surfaces of the crankshaft and bearings and rust flakes off as a gritty abrasive when the engine is operated next. Once the rust has formed there is nothing much you can do about the damage that has already been done to the surfaces. However, the damage may not be critical if caught early. The important thing is to remove what rust you can before it flakes off and works its way through the engine as an abrasive.

Remove the prop nut, prop washer and thrust washer so you can see the front bearing. Use Pacer Degreaser to clean out the engine. Read the cautions on the can. Work outdoors and wear eye protection and gloves. Spray the degreaser inside the crankcase first while holding the engine slightly nose high so that as you spray the back of the crankshaft and the rear bearing, the excess degreaser washes back and flows out the back of the engine.  This will knock loose and carry away some of the rust. Then hold the engine nose down and spray the front bearing. Let the engine dry.

Once the engine has dried off, thoroughly douse the rear bearing, front bearing and crankshaft with After Run oil. Drip after run oil into the rear bearing from the back of the crankcase, into the crankshaft area through the carb inlet and into the front bearing from the front of the engine. Rotate the engine by hand 2 times and then flush all of the oil away using the Degreaser again. Flush thoroughly and let dry.

Repeat this process three times, each time rotating the engine by hand for a greater number of rotations. What you are doing here is using lots of lubricant as you rotate the engine and flake off rust. The loose rust ends up in the lubricant and then carried away as you flush with degreaser.

Lubricate the engine again with plenty of After Run oil. Let it sit a day or so before operating. Rotate the engine by hand 10-15 times and then flush one more time with Degreaser and let dry. Apply plenty of After Run oil, reinstall the back plate, thrust washer, prop washer and nut. Rotate the engine 2-3 times by hand.

You can now run the engine. This process won't undo any damage that the rust has already done but it will help to reduce the amount of rust in the engine and the abrasive action of the rust as it flakes off.

From this point on, make sure you use After Run Oil after each day of operation. See your Owners Manual for maintenance and cleaning information and review our Rust Prevention tips and our tips for long term storage of your engine.