wpadams

I just took apart a gummed up PAW 19. I marked the back of the conrod and piston but did not mark the liner alignment. There is no obvious alignment with the circumferential porting and no register pin. I guess it only matters to get the wear pattern to match that of the piston or is there some secret code or mark to look for? I want the right alignment for reassembly....

ffkiwi

AFAIK there is no code-secret or otherwise involved! You've only got a 1 in 3 chance of getting the alignment back the right way....could be worse-with some engines its 1 in 4 if you didn't bother to mark the alignment before disassembly. Shows the merits of using a pin to positively locate the liner. Personally-where PAWs are concerned I always make a mark at the top edge of the liner, at the front, before disassembling any further....I use a Dremel cutoff disc to just kiss the edge.....makes a neater job than a file.....and a scratch mark with a scriber point can be overlooked. If the liner comes out with the fins attached on initial disassembly I mark lower down with a felt marker till the components are separated then mark the top properly as before.
In theory.....at least you might be able to see some internal wear patterns-but a lot would depend on how much running the engine has done-and how much cleaning was done before reassembly.

ChrisM
'ffkiwi'

wpadams

FWIW I devised a method to work out the right orientation that is perhaps better than guesswork. I tapped out the contrapiston and oiled up the bore and piston. Holding the liner in place by hand I twirled the crankshaft, feeling for how freely the piston rode up and down in the bore. One of the 3 orientations seemed freer than the other two so I took that to be the correct orientation.

ffkiwi

'
That's probably about as good as you can do realistically-likely to be correct...and you wouldn't pick it up with the contra in place....

ChrisM
'ffkiwi'

qazimoto

My Feedback: (1)

If it turns out in due time that it wasn't the right choice just send it back to PAW for a rebore.