Seized pistons

[lcdrjoe]

New owner of an 87 GL1200 Interstate. Got the bike cheap, but the engine is seized up due to water intrusion into the cylinders through the intake. I've removed the heads, cleaned them up, lapped the valves, and reinstalled them. I've got the cylinders full of Marvel Mystery Oil right now soaking. Or at least I've got them as full as I can as they are horizontal and the exhaust valves are low. I know there's many formulas for soaking stuck pistons to free them. I'll probably throw in some acetone and automatic trans fluid too. My problem is that at least some of the valves are open partially. I've tried to rotate the cam so that the intakes are open (timing belts are removed), but I'm not sure that is totally successful. I've considered taking the cams out and that should seal up the heads. I've thought about removing the exhaust pipes and stick some rubber plug in the outlets. I'm hoping maybe you guys have some other trick. This is a project and it'll take a while to even get her running.

[Rambozo]

You can just do one side at a time by laying the bike over on it's side.

[DenverWinger]

Fill the crankcase all the way up to the oil cap with Deisel or something and attack the problem from the inside, too...

[lcdrjoe]

I've let her sit with oil/marvel/atf/diesel/acetone/... whatever I could get my hands on down the plug holes. Also took up the DenverWinger's idea and filled her up with diesel. I'd already tried Rambozo's suggestion. After a week like that, going out there every day and trying to get her to spin with the crank bolt, I went out there today and took the heads back off. Proceeded to put a 2x4 cut to fit the cylinder size and wacked the most suspicious piston with a hammer (on the 2x4, of course), then a bigger hammer, then wacked it with a big crowbar . Looked and it appeared that the crank had turned just slightly. Put a wrench on the bolt and tried to move it back, with assistance of a cheater bar, and got movement . From there, in about an hour, I was rotating her with the starter. Freed up. Heads are still off. Put a plug in a boot and tested and got a small weak spark. Pretty stoked about that. Thanks for all the help guys.

[Rambozo]

Congratulations. It's always nice to get it moving. I've done the wood block thing more than once. (BTW try to line the wood up over the pin bosses of the pistons, not the unsupported parts.)
Who knows you might even get it running, and if you're lucky it will burn more gas than oil.