I'll second PB Blaster, really good stuff. I've never freed an engine with it, but I've used it on rusted bolts and stuff on my car (Newfoundland is the world capital for rust :x ). Sprayed it on and left it a day or two and it worked great. Anytime I know I'm going to work on a part of the car, I'll spray it a day or two in advance, saves a bit of swearingBird76Mojo said:I'll say it again. PB Blaster is the only thing I'll use in situations like this. It unlocked a Yamaha CT3 for me that looked worse than that. It'd been sitting outside full of water for probably 15 years, with NO HEAD ON IT. Squirted the jug full and smacked with a 2x4 and the jug came off. Then I squirted a liberal amount in the crankcase, and the crank was free within a day if I remember correctly..
KERRY said:Acid will dissolve the rust. Phosphoric acid is commonly used - glacial acetic will work, probably as well. They may not do the aluminum pistons much good, but I'm guessing they're already not in prime shape. I think I've heard that acid will make a brownish stain on the side covers, but they're probably off, anyway. One of the most effective penetrating solutions is a mix of half ATF and half acetone. In lab tests, it outperformed the commercial products. Of those, KROIL tested as best. I worked at a Benz dealership ages ago - we used an ærosol product that actually got hot when it was sprayed on a rusted part. I wish I could remember what that was - it was quite effective.
gaillarry said:I like the idea of half ATF and half acetone, it's readily available compared to Phosphoric acid. I might try that mix tomorrow.