TS 125 seized engine

[JonnyK]

I have just baught a 125 ts 'weather seized' I've taken the head off and it looks very clean. I took the carb off and felt underneath and it feels rough. Someone must have tried soaking it as the head was full of oil. I've heated the head up from the outside lightly with a small blow torch and managed to tap the piston down about an inch or so. Any other ideas how to free it off?

[radiograf]

Try spraying the bore with a penetrating oil (around the top of the piston) and leaving it to soak. WD40 is the first that comes to mind, although there are many others, some which are specificaly designed to release seized nuts, and have antirust ingrediants. The best place to find these is your local car spares shop.
An old trick is to bolt a plate across the top of the barrel that has a threaded hole above the piston. A bolt is then screwed down onto the piston, applying a constant pressure. Either the piston will move down, or the barrel up.

[JonnyK]

Thankyou for the tip, I like the threaded plate idea (a bit like a crank extractor for bikes) might give that a go.

[mirmay]

Try spraying the bore with a penetrating oil (around the top of the piston) and leaving it to soak. WD40 is the first that comes to mind, although there are many others, some which are specificaly designed to release seized nuts, and have antirust ingrediants. The best place to find these is your local car spares shop.
An old trick is to bolt a plate across the top of the barrel that has a threaded hole above the piston. A bolt is then screwed down onto the piston, applying a constant pressure. Either the piston will move down, or the barrel up.

Or the bolt will go through the piston!! I have heard that Coca Cola works wonders but this may just be folklore.

[radiograf]

Place a piece of wood between the bolt and piston, should solve that problem. Coke contains phosphoric acid, the same ingredient that rust curing products contain, just a lot more dilute.

[mr_luke]

I'd go for a block of wood on top of the piston, and gently tap it, while you (or preferably an assistant) apply pressure to the kickstart. Once you get to the bottom of the stroke, you can place bits of wood under the barrel to hold it away from the crankcases, and repeat. Obviously soak it in as much oil/wd40/paraffin/diesel as you can for as long as you can bear first! This has worked for me in similar situations, and has the advantage that you are applying most of the force through the gudgeon pin, rather than through the crown of the piston.