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With the rings, they dont need much tension they just need sharp edges (and a bit of tension) because the blast forces them to the bore if the rings are blunt then that gives the gasses a way past the rings and forces down past the rings
 
if your piston looks ok,
and doesn't move around much in the bore, you may get away with just replacing the rings and giving the bore a clean up with W&D ?

there are a couple of types of Head Gaskets used in them.
one is a copper gasket, the other is a cheap alloy one, you should be fine to reuse it.
if it is copper, you can re-Temper it, by heating it up on your gas burner until it glows red
then carefully pick it up with some tongs/pliers and quickly drop it into a container of cold water.
it is now ready to fit once you replace the rings.
 
the other thing to check with the rings is the gap
these were worn and the gap was pretty big when the piston is in the bore
this lets some compression past so when it fires, the spark isn't as big, and the engine runs less efficiently

 
Ok , Thanks so much for your help. How do you tell if you need new rings or piston with out taking it all apart ?
 
Ok , Thanks so much for your help. How do you tell if you need new rings or piston with out taking it all apart ?
Usually a rattly top end, or take your pipe off, then cycle the piston a couple of times looking at the bore and piston to see whats happening in there..

it gives you a rough idea, you can also push on the skirt of the piston and feel a little for excessive movement but you will probably hear it before anything other
 
It sounds ok. I might change the fuel and see what happens. But for $20 i'm kinda keen to do a rebuild :) It looks very easy. Thanks for your help guys
 
pull the head and barrel off first to check piston condition and size
 

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