broken con rod

[Andy stubbs]

Got hold of this fourty minus to do strip and un-cease for a mate, cannot move piston in cylinder bore and drive shaft is well stuck on the end of the crank shaft square drive. Think this has either been for a dunk or stored in a damp place or on the back of a boat near salt water for a long time by all the corrosion I am finding, not sure how all the debris, corrosion has got into the crankcase, have knackered con rod cap trying to remove it as the screws were well ceased so will need a new rod if anyone has got a spare please contact me
Good points are the gearbox seems ok, but have not stripped it yet to find out what the gear set or anything else is like. Could anyone tell me what the weak points are of these gearboxes and what to look for

[water bug]

Suggest pounding out the piston using a wood dowel roughly the size of the bore. Piston can be cleaned off with scotch bright or a fine wire brush. Likely rings are "toast" or knackered. Crank likely OK once thoroughly wire brushed. use 400 grit emery cloth to brighten the bearing surfaces. A 40+ or Feather rod will work. Gear box : total clean out, wire brush gears, even if some rust , likely OK. If possible remove pinion carrier, using the shop repair manual instructions. Then clean pieces. GOOD idea to buy a shop repair manual from John W at SOS. That will tell ( almost) all you need. They are never as bad as they first look. Cheers. Let us know how you do.

[Andy stubbs]

I have tried to knock the piston out with a wooden dowel but it will not budge, it has been soaked with WD40 and light oil for a few weeks before trying to free it off. The main of the rust seems to be between the rings around the piston through the air/fuel intake spigot port, might try and soak it in diesel oil/ engine oil and see if this helps as previously suggested on a previous thread.
The crank seems ok on quick visual inspection, the gearbox rotates freely but have not drained the oil/ sludge and taken apart yet as want to free off piston first
I have the manual from John at SOS and it is very helpful

Thanks Waterbug

[Charles uk]

Your trying to push the piston into what might well be, the tightest part of the cylinder, the upper part of the bore looks reasonable try driving it the other way, if you have a friend with a lathe get him to make you a 200mm long ally tube with a 44.5mm OD & a 37mm ID with a small step at the top so it locates inside the piston but puts all the pressure on the piston skirt then put it in a big vice, once you've got it moving , then you can lube it.

Scotch bright any corrosion in it's path, before you push it.

[Horsley-Anarak]

I would warm the piston up quite hot without melting it.

I find that a bit of thermal shock always helps, spray with thin oil WD40 as it is cooling.

As the piston is near the bottom of the stroke I would continue knocking it out that way.

It the rust does score the bore it will be doing it at the bottom, which will have little effect on the compression.

A round piece of wood should do it ok.

H-A

[Andy stubbs]

Tried warming the block up with a blow lamp to expand it before hitting it with wood and a mallet.I'm going to leave it to soak longer and have another go in a few weeks trying various things that have been mentioned, thanks for the replies everyone and will post how I get on soon.

[water bug]

Warming is good. Get a bigger hammer, a BIG steel one. Hit it harder. Support the cylinder bottom. It will come. With a reasonably fitting dowel, it is very doubtful you will harm the piston. Art

[Charles uk]

I've seen more than 6 pistons with holes punched in them, some very deformed, even to the extent, that the land above the top ring had expanded to a perfect fit in the bore, like a core plug!

So when Peter 40tpi came up with the suggestion that it might be much better to remove with pressure from the bottom for cylinders with removable heads, & asked if I had any tube that would clear the con rod I found him a bit of ally scaffold tube.

[water bug]

Charles, That is a great idea. Since it worked with that VERY rusty bore, It should work with almost any cyl/piston. I may have to make a set of those too. GOOD thing there are only two Sea Gull Bore sizes
( mostly). Art

[Andy stubbs]

Good ideas for removing piston's, I stuck with the method of loads of heat, soaking in oil and found a socket that fitted well down the bore with minimal clearance and a lump hammer to hit said socket with. A few good blows with the hammer and it started to move, the piston looked ok, bore not too badly scored but while cleaning the waterways out found a crack and on closer inspection found another crack in the cylinder wall, bugger so find another engine time.