Stuck Piston Help

[RTwo]

Hi all,

I'm currently restoring a B50T and today I started on the engine, I'd earlier removed the head to find the piston totally corroded in the barrel.
At the time I just filled the bore with WD40 and left it for a couple of months.
I'm now struggling to move it at all, I've spent most of the day with a blow torch and a big mallet trying to move the bloody thing 

It's stuck about 30mm down the bore so I can lift the barrel (and piston) up and down off the cases a similar distance.
My method so far is to lift the engine up by the barrel and then trying to beat the piston down.
I thought about removing the barrel studs to allow me to twist the barrel a bit but I'm not sure if I risk more damage to the rod assy. etc.

Any ideas?

The liner is toast so that'll be getting replaced but I'd like to try to save the piston.

[Mike Farmer]

 

Try Automatic Transmission Fluid. Ive never used but have heard of sound results. Your piston is probably toast as well.

Mike

[ferretjuggler]

A mixture of ATF and thinners is supposed to be the most powerful penetrating lubricant by a long margin.
I think that if you want to save the barrel casting and the rod, you've got to accept that the piston/rings/liner will have to be sacrificed.
Previously I've punched the core out of an old spark plug, filled it with weld, and then drilled and tapped for a grease nipple.
Worked for me on a locked up XS650.
On the other hand it will cost you a head gasket, and has the potential to cause some serious damage if you go OTT.
I'd seriously consider completely drilling away the crown of the piston, and then sawing through the skirt to split it.
Good luck.

[RTwo]

Cheers guys
Yeah, the nuclear option may well be the only way but I think I'll persevere with a few less destructive methods for now and progressively up the ante
It's had a mixture of ATF and acetone sat in it for 24 hrs or so now so I'll see how that fared.

I also have some concentrated sulphuric acid that should attack the rust way before it starts on the aluminium (I think) but it's seriously nasty stuff and would end up down in the engine if it worked

[DANFINN]

Have you tried Diesel? That's good for stuck nuts bolts and things. Good soak for about a week

[Mike Farmer]

 

Something you might try as well as ATF. Get a block of wood the width of the bore and protruding above the top by 5 or 6 mm then bolt the head back on as tightly as possible. Retighten every couple of days and it should "give". You will need to unbolt the barrell from the crankcase that way you will not be pushing against the crank (in case the crank is also stuck)

Mike

[rhyatt]

Diesel or paraffin down the bore , head off and a hot air gun getting the barrel really hot.
Then a good thump with a hammer driving a piece of wood on the piston crown downwards.
Someone even suggested coke a while ago, what do you have to lose.
Even better if you could suspend the bike from the garage ceing by straps etc around the barrel, just have gravity and the weight of the bike  and do the hot air gun , diesel etc.

[RTwo]

The nuclear option prevailed 
Nothing worked, my last effort was with a modified bearing puller and a blow torch



But it's out now 



So... new liner and piston kit needed. Any advice? I take it I may as well just go back to standard bore size?
There seem to be piston kits available for around £130, does anyone know if they're OK?

Thanks again all

[DANFINN]

I'd go for a reline and new piston.  Get a recommended firm to do it