cylinder liner thoughts

[Triton Thrasher]

"Practically all the compression sealing should be done by the top ring." Especially those engines that only have one compression ring!

Racers!

[BSA_54A10]

Do a quick fit up and check where he pits are with respect to the top of the top ring.
Most of the compression is done by the second ring in an case .

Practically all the compression sealing should be done by the top ring.  The second plain ring does some useful oil scraping.

The top ring is called he fire ring for good reason, it takes he brute force of the combustion
The first set of gapless rings I installed I fited the gapless one on the top and they failed myserably
Swapped them around, gapless 2nd ring, worked like a dream

According to some conversations with Total Seal, they suggest opening the gap on the top ring and closing the gap on the 2nd ring regardless of weather  am using gapless or standard rings.
Too little gap on the top ring  prevents suffcicient gas pressure getting behind the second ring fast enough to create a proper seal.
 has been taught the top did all the work but apparently it should be the 2nd.
In use I have run more than one engine with pitting in the bore because new barrrels or liners were beyond my finances at the time
Unless the pit wa almost a full ring, the worst case was an engine that was a little more smokey than it should have been.

[BSAmoto]

One of my quick Norton engines exploded long ago and left a few dings in the upper end of the LH barrel. I rebuilt the engine without reboring the barrels as they were not worn out - except the dings. Ran a hone through and put used pistons in. No smoke as the dings cannot collect oil - they are all above the upper travel end of the oil scraper ring. So check location, if yours are as high up the barrel as they appear, I would use as is.

[BSA_54A10]

Swarfy, I normally agree with all you say, but filling with braze? I'd rather leave alone.

S O P with large marine deisels

[Radlan2]

Hi all
       Just to revive this older post the question to my mind is that in order to fit the liner to the barrel, which already has a reputation for breaking above the base flange, is further weakened. I measured the casting above the flange which is 81/82mm I have seen liners for A10 advertised with an O.D. of between 73 and 80 mm. Surely this a has serious risk of failure when the wall thickness of the original casting is best case 4mm and worst case 0.5mm!
      So much better if one of the piston suppliers made +0.080" pistons which gives a wall thickness of 4.5/5.0mm, I know Cake Street had a batch made, if only these were availiable again.
          Cheers
                      Chris

[muskrat]

G'day Chris.
I just threw a set of +80's in the Cafe's barrels that had been previously sleeved (aprox 75mm od). Still plenty of meat. She'll be running 12:1 comp but the head is through bolted to the cases.
If you could find a old bike or car shop, take a pin & piston to compare with another make of bike or even car. A mate has a diesel piston in a Yammie XT600
Cheers

[RichardL]

My sleeves-in-waiting are 73mm O.D.

Richard L.

[Radlan2]

Yes Thanks Richard, Musky
        My instinct runs against such a thin liner, and I think the 80mm O.D. liner advertised has been read from a "spec sheet" for a 70mm piston to give a 5mm wall thickness not realising the block is only 81mm. I am no expert so if the original casting is bored perfectly and the spun cast liner if perfect and with the correct interference.. then the font of the engine gets the cold air will a liner only 1 or 2mm thick be ok? I dunno.
         Alternative pistons are, I think, the answer and the prime candidate must be 650 pre-unit Triumph, air cooled and with a standard bore of 71mm thus giving two rebores after the A10 +0.060 max, and leaving the original barrel 4.5/5mm thick. There is a problem though, the small end is 11/16" and the gudgeon pin hole is in a different position relative to the top of the piston which means the Triumph piston would come out the top of the block. So to do this you would need a new pair of special rods and a new pair of pistons and re-bore. That lot would set you back at a guess around £600 which is probably why people go for liners!
          Love to try  it, anyone felling ftush.
                  Cheers   Chris
               

[Radlan2]

Correction, its not that the piston comes out the top of the barrel, it's that it doesn't reach the top, by about 7mm I  think. So a longer rod  is required, still need special rods though.
           Chris

[muskrat]

G'day Chris.
I think sleeving back to standard is your best option. Richards 73mm sleeves still gives one or two oversizes for the future.
Cheers

[chaterlea25]

Hi All
Just thinking about this??? what about B31 pistons which are also 71mm std
If I think of it I might compare them tomorrow, If I can find a B31 piston in the melee

John

[rocker21]

many years ago i fitted a +60 A10 piston into a B31 and it fitted, needed a spacer under the barrel  as the piston came out, was not much think is was about 3mm so an alloy spacer was made, worked a treat rode to Holland on it.

[chaterlea25]

Hi All
Yes the B31 piston compression height is too low compared to the A10

John

[RDfella]

I don't have my 60's piston catalogues in front of me, but the B series had three different lengths of conrod (the ZB had the longest, the CB was shorter and the DB shorter still) so presumably gudgeon pin to crown height changed as well - ie there might be a more suitable version that would do.