CB200 seized engine

[Fretless Six]

Alright, so I just got my new bike. It's a '74 Honda CB200 and the engine is seized up from sitting for twenty years, the frame and everything else is in beautiful shape. The cam chain won't budge and I can't get the head off to get at the pistons. I poured some Sea Foam into the spark plug holes and now I'm waiting to see if I can get it to budge, is there anything else I'm missing?

 

[Big R]

Cut the cam chain off for starters. They aren't terribly expensive to replace and a new one gives peace of mind.

Did you try Aero Kroil or PB Blaster first? Both would do a better job than SeaFoam.

 

[Fretless Six]

No, I'll try those next if for whatever reason I can't get anything to budge.

 

[teazer]

Rich is spot on. Grind the ends off both pins on a link and try not to grind anything important like the head...

Then push that link out and pull the head off. It may need a pin punch to push it through because the pins are riveted in place and swell to fill the hole in the side plate.

 

[Keogan]

Theres a few threads on here that have your particular problem, I know the BSA restoration had a similar problem and it took him months until he literally set it on fire to unseize it. I wish you the best of luck, I can't wait to ride my cb200 all over.

 

[swan]

I have tried every possible chemical mixture on severely frozen pistons ( ATF, Diesel, Acetone/ATF, SeaFoam, Deep Creep, PB Blast, Marvel Mystery Oil, WD40 etc) and the best method is to fill the cylinders with a mixture of gasoline and ATF or Marvel, a cloth wick, light it and let burn for an hour. The heat expands the cylinder wall allowing the penetrant to work on the rust and rings.


Check it out.