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Cylinders - sleeve or replace?

  • 09 Mar 2026 5:43 PM
    Quote
    Message # 13607654
    Vilmer Berglund

    Hello,

    A few months ago I bought my first 101 Scout. It is a 1930 45 cu in with the Bosch electrical system. When I purchased the bike the engine was only partly complete, so I have disassembled it for inspection and rebuilding.

    My biggest problem at the moment is the cylinders. One of them has several scratches in the bore. The scratches are clearly visible and can be felt with a fingernail (see photo). When measuring the ID I got an alarming 74.8 mm (0.07" oversize i think).

    Would it be possible to install a sleeve in the cylinder without risking the cylinder foot breaking off, or creating issues such as pre-ignition from the exhaust valve seal? The alternative would of course be to buy new cylinders, but as a Swedish student my wallet suggests that I try other options before buying new ones :)

    If new cylinders are the best solution, which ones would you recommend?

    Thank you for any advice or recommendations.

    Best regards,

    Vilmer Berglund


    3 files
  • 10 Mar 2026 12:40 AM
    Quote
    Reply # 13607758 on 13607654
    Tim Raindle (Administrator)

    Hi Vilmer, are the scores all the way down the bore or just at the bottom ? At your current measurement, you MAY be able to run +060 pistons with a loose fit, with a very light hone to break any glaze. You may be able to fit a thin sleeve, but it would need to be stepped thin at the base below ring travel to avoid weakening the cylinder catastrophically. Perhaps it may be worth a call to a renowned Indian shop such as Jorgen Sundberg at Grevbo. Someone who knows scouts well may be able to give you a more balanced view in person. If you could take either of the options above , it would probably be far cheaper than a pair of new repro cylinders, and if you could run a sloppy fit 060 piston it may well last you long enough to find a better pair of used cylinders, or save up for a new set. 

    Hope this makes sense, keep us informed of how you go,

    cheers, Tim R
  • 10 Mar 2026 5:01 AM
    Quote
    Reply # 13607794 on 13607654
    Philip Jenner
    Vilmer Berglund wrote:

    Hello,

    A few months ago I bought my first 101 Scout. It is a 1930 45 cu in with the Bosch electrical system. When I purchased the bike the engine was only partly complete, so I have disassembled it for inspection and rebuilding.

    My biggest problem at the moment is the cylinders. One of them has several scratches in the bore. The scratches are clearly visible and can be felt with a fingernail (see photo). When measuring the ID I got an alarming 74.8 mm (0.07" oversize i think).

    Would it be possible to install a sleeve in the cylinder without risking the cylinder foot breaking off, or creating issues such as pre-ignition from the exhaust valve seal? The alternative would of course be to buy new cylinders, but as a Swedish student my wallet suggests that I try other options before buying new ones :)

    If new cylinders are the best solution, which ones would you recommend?

    Thank you for any advice or recommendations.

    Best regards,

    Vilmer Berglund


    60 tho oversize  should be set as the practical  Limit   70tho  is really stretching the   friendship   ...  If  the cylinders were to be sleeved they should be stepped sleeve , The bottom is really thin  and weak .  Ive used Repo Cylinders  that I bought from  Tasmania  and they are great...  Now sold in Victoria.  I do run pluss 60s in my 28 101  but  im very respectful how i ride.

    Regards Phil
  • 10 Mar 2026 5:06 AM
    Quote
    Reply # 13607795 on 13607654
    Philip Jenner

    Looking  at the bottom of your cylinder  It  looks to have a line  around the   edge  and is possibly already sleeved .    Your inlet valve seat is also  well undercut.....  I would personally be looking at  new cylinders .

     regards Phil
  • 11 Mar 2026 4:55 AM
    Quote
    Reply # 13608261 on 13607654
    Ken Lee

    I'm not an engineer but have been rebuilding engines for more years than I care to remember , so thinking IF there is already a liner , is it possible to remove it and put a thicker liner and use suitable smaller pistons , maybe a few cc smaller , there's a multitude of pistons out there that one can find ? my '18 Harley is fitted with Bedford lorry pistons , Henderson with Douglas pistons . Just asking for interest sake and always wanting to learn more ! Good luck anyway Vilmer . Ken
  • 12 Mar 2026 3:41 AM
    Quote
    Reply # 13608763 on 13608261
    Philip Jenner
    Ken Lee wrote:

    I'm not an engineer but have been rebuilding engines for more years than I care to remember , so thinking IF there is already a liner , is it possible to remove it and put a thicker liner and use suitable smaller pistons , maybe a few cc smaller , there's a multitude of pistons out there that one can find ? my '18 Harley is fitted with Bedford lorry pistons , Henderson with Douglas pistons . Just asking for interest sake and always wanting to learn more ! Good luck anyway Vilmer . Ken

    Agree Ken  sleeving smaller  is sometimes an Option.  Ive seen Indian cylinders  Boored so far  that the Place  thats relieved  for the Base studs   is  bored through   .  Ive also heard of complete  silver sodering the Liners in.  Ive seen broken  Indian cylinders  from Over boring... Making a decision on New  Cylinders  is  not easy  and not cheap.   But Ruined Crank cases  that can easily happen  when cylinders disintegrate  is also a issue to consider!

    Regards Phil
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