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WLA pistons
Old Fatty
1 month
G'day all, my brother is rebuilding a WLA engine and these pistons come out of it. Just out of curiosity, does anyone know they are from? The manual shows the pistons with all rings above the pins, but these have the oil ring at the base of the skirt. Can't find any info on this style anywhere. Thanks, they are going in the bin anyway. Bob.
B0nes
1 month
Not 100% sure, but I have seen similar looking pistons from an old hot rod that was running a V8 Ford flathead. It also had oil rings below the pin just like these.
tussuck
1 month
very interesting...
https://gordsgarage.wordpress.com/2013/08/08/i-like-a-piston-with-a-short-skirt/
https://www.quora.com/Why-dont-pistons-have-a-second-set-of-rings-at-the-bottom-to-prevent-them-from-tilting-in-engines-and-scratching-cylinder-walls
tussuck
1 month
https://www.hemmings.com/stories/article/three-ring-circus
obisteve
1 month
Old Ural 650s had 4 ring pistons, the low compression pistons any way. The higher compression later pistons, which can be dropped into earlier motors if you're brave, are 3 rings. Got a nagging feeling that Guzzi Ambassadors had 4 rings too, but might be rong.
Gonna edit this, was a late night post. Meant to say 4 rings, with the oil ring near the base of the skirt.
Piston design has sure changed since I've been playing with them, as revs have risen and tolerance for oil consumption has dropped.
Old Fatty
1 month
Turns out they were made by a Melbourne company called Polson Pistons. The company was last heard of in the 1960's.
obisteve likes this post
obisteve
1 month
Just out of curiosity, are they anywhere near standard bore or has it been punched out?
obisteve
1 month
And just for fun, extracts from Polson's bike piston catalogue from the 50's, but because of my Norton background, the selected page is for their Norton range.
http://www.vintagenorton.com/2022/11/polson-pistons.html?m=0
To access the catalogue you have to click through on the link that's in the page that opens from the link I gave.
Old Fatty
1 month
Quoting obisteve on 17 Jul 2024 10:58 AM
edited: 17 Jul 2024 10:58 AM
Just out of curiosity, are they anywhere near standard bore or has it been punched out?
The barrels measure 32 thou over, so I say at some time it was taken out to 30 over and then 2 thou wear. The pistons, though, were 20 thou smaller than the bore, so there was a fair bit of wobble when we took it apart. It will be going to 60 thou over with pistons to match.
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