SailNet Community banner
1 - 9 of 9 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter · #1 ·
Hello,

I've got a locked Yanmar SB12. Tried soaking oil above the piston for a month and still cannot hammer the piston south. Pulled the engine and have it upright but am still unsure of the problem (bent rod?).

Are there any pros in the Annapolis are who could take a look? I'll, of course get the greatest wine and lunch out there.

I'm under spa creek drawbridge if you are nice enough.

Thanks guys,

Peter
202 468 8660
 

·
Registered
Joined
·
4,721 Posts
Turn it on it's side and remove pan and con rod cap(s) end. Can you turn the crank?. Very careful not to damage the crank journal with the studs.(wrap a rag around) Hardwood block and large persuader on the conrod . If piston is already at tdc ridge may prevent more travel that way and best to persuade down with crank turned down Then ridge remover. Look for anything bent. Usually on multi cylinder engine that you can turn measure distance from piston tdc to top of block to find the short one.(or two out of four in my case). The gears in front, cam and harmonic balancer.,should not be jammed with broken bits.If piston is tdc hammering down won't help and needs a breaker bar on the crank.
 

·
Registered
Joined
·
167 Posts
Probably past the point of being useful since you already soaked with oil, but I always use transmission fluid for that. There are a lot of detergents in the trans fluid and it works a little bit harder at getting things unstuck. I have used it to soak old rusty tools that came up great, and heads and cylinders that had gotten water in them. Came up nice. Good luck at any rate.
 

·
Registered
Joined
·
6,689 Posts
After disconnecting the con rod, remove the head, and cut a chunk of wood the same size as the piston and place it firmly on top of the piston. Then, using a 2-pound maw, smack the wooden block a couple times. If this don't do the job, you may need a bigger hammer.

There are some products out there that do a lot better job of penetrating corrosion than motor oil or ATF. Even WD-40 or CRC is better than motor oil. Machine Oil, which is used by most machinist working with lathes and milling machines really penetrates well.

Gary :cool:
 

·
Registered
Joined
·
4,721 Posts
As I said earlier, smaking the piston won't do any good if it's tdc. gotta turn the crank out of the way .see above. My first rebuild at 16,a '41 plymouth, had sat with head off and full of rain water for years .This one doesn't sound difficult.Keep us updated as a learning experience to others. Stuff like ridge removal, honing, plastigauge bearing shells will be entertaining.
 

·
Registered
Joined
·
127 Posts
pb blaster in a yellow and white can is about the best stuff out there as a penetrant. Please don't hammer on a piston with it connected to the crankshaft, if that didn't happen to be the one that's stuck you just ruined your rod bearing insert. soak it with the blaster and bolt a bar across the flywheel for leverage. If you can get something on the flywheel to hit with a hammer to jar it into rotating that wouldn't cause any additional harm.
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top