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Seized ducati piston
Benzine - 15/10/13 at 05:55 PM

I have a single cylinder diesel engine:




The piston is seized at TDC so placing a block of wood on the piston and hitting down isn't going to work is it? Hitting the flywheel with wood isn't working as it's spoked to let air in and it splits the wood. Anything else I can try before splitting the crank case?

steve m - 15/10/13 at 06:03 PM

You hitting the wood as someone else turns the crank?

soak in vinegar?

ken555 - 15/10/13 at 06:04 PM

50/50 petrol and AT Fluid into cylinder (I'm guessing it's not flush to block)

Set fire to the mixture and let it burn for a long as possible, then let it cool.

Now try the crankshaft bolt to see if it will move.

I've also seen people put a few rags in the mix to keep the fire going longer.

Basically the heat/cool cycle to loosen it.



[Edited on 15-10-13 by ken555]

theconrodkid - 15/10/13 at 06:12 PM

Boat engine ?,i did one many years ago,plus gas and a long wait freed it but heat would seem the best option as it,s out

oh and i couldnt get any parts for it,not even a gasket so try not to break anything.

[Edited on 15/10/13 by theconrodkid]

Benzine - 16/10/13 at 07:20 AM

quote:
Originally posted by ken555
50/50 petrol and AT Fluid into cylinder (I'm guessing it's not flush to block)

Set fire to the mixture and let it burn for a long as possible, then let it cool.


Worth a go I have ATF (that's what's on top of the piston in the pic) It's flush to the block, I can only get a tiny bit of liquid on there, although the dish in the piston holds a bit/

quote:
Originally posted by steve m
You hitting the wood as someone else turns the crank?

soak in vinegar?


Not yet, it needs a 2" socket for the crank but, not got one that big, only as big as 1 13/16. Not even my massive adjustable spanner fits on it



quote:
Originally posted by theconrodkid
Boat engine ?,i did one many years ago,plus gas and a long wait freed it but heat would seem the best option as it,s out

oh and i couldnt get any parts for it,not even a gasket so try not to break anything.

[Edited on 15/10/13 by theconrodkid]


It was from a water pump as far as I know, I don't know much else about it. Yeah they seem to be rather rare! I saw it for sale locally and fancied a small project that would fit on my workbench.

SCAR - 16/10/13 at 08:01 AM

If its at seized at TDC there's no point hitting anything, you will do more damage than good. At TDC the shock travels straight down into the crank without trying to turn it. You will probably bust the piston before it moves.
You need to keep applying a thin oil (like wd40) to the piston from the top and the underside and hope it penetrates the bore then try to move the piston via turning the crank. You could combine this with applying some heat as evenly as possible to the barrel.
You will have to split the cases as you will need to examine the crank/bearings and take the piston out for inspection
The longer you take the more likely it is to move without breaking.
Good luck

britishtrident - 16/10/13 at 11:51 AM

PlusGas and Rock the crank back and forwards ,don't use excessive force, just try to rock it a couple of dozen time, soak it again and leave it for a while, it might take half an hours rocking over couple of weeks but eventually it will free.