Pub quiz,identify the piston!

[mikeyboy]

Hi all ,bought these 1000cc pistons off eBay for £2
The seller was unsure of the bike they came out of,can't say I can recall ever seeing flat top ones
Anyone know what model they might be for
Thought I might bore out a set of 800 barrels for them

 

[AberdeenAngus]

R100T ?

 

[mikeyboy]

R100T ?

Is that a guess??

 

[Beemerboff]

Look like the so called squish band pistons fitted to some of the late 70's bikes with cast iron liners - it looks like there is a fair bit of metal above the top ring groove.
Boring out liners isn't always a success, it needs a torque plate and the barells hot, and someone who has done a few and knows what he is doing, and even then there isnt a lot of meat to play with.
There are more than one type of cast in liner, I have seen sections of barells which had a proper Alfin insert and others with just a flanged tube, and they would need a a different approach too.
I had a R75/7 bored out to 900 and it was right at the limit - you could see where the fins were by rings of different wear on the honing, there just wasnt enough meat left and the barell was expanding like a concertina.

 

[mikeyboy]

Look like the so called squish band pistons fitted to some of the late 70's bikes with cast iron liners - it looks like there is a fair bit of metal above the top ring groove.
Boring out liners isn't always a success, it needs a torque plate and the barells hot, and someone who has done a few and knows what he is doing, and even then there isnt a lot of meat to play with.
There are more than one type of cast in liner, I have seen sections of barells which had a proper Alfin insert and others with just a flanged tube, and they would need a a different approach too.
I had a R75/7 bored out to 900 and it was right at the limit - you could see where the fins were by rings of different wear on the honing, there just wasnt enough meat left and the barell was expanding like a concertina.

Hmmm,
Might take some measurements,
See what sort of piston protrusion I will have,

 

[mikeyboy]

My initial thoughts were a low comp piston but comparing to others I have ,it looks likely that it will protrude slightly?

 

[mikeyboy]

My initial thoughts were a low comp piston but comparing to others I have ,it looks likely that it will protrude slightly?

Had to cut the last post short,as I needed to go out,
So to add;
The valve pockets seem quite deep for a low comp piston,will take another look on Monday

 

[mattgirv]

R100T ?

Yeah, there's an early R100RS with flat pistons here in this album, looks eerily similar - https://www.flickr.com/photos/brook-reams/albums/72157675205320686/with/31184980820/

 

[mikeyboy]

Those look like the ones,
He replaces the pistons later on in the photo build,
For 9.5 to 1 ,so I assume my pistons are lower comp.
Thanks for posting