Berkshire 100/6B?

[KJDonovan]

I have a question for the Sachs guru's here; did the 100CC Berkshire ever come with a 6B bottom end?

 I ask because I am getting ready to start on a mid-74 (406-XXXXX) CMF that I picked up several years ago.  When I got this bike it had no motor, but I always made the assumption that it was a Berkshire based on the red airbox and the metal box attached to the swingarm for mounting Sachs engines to CMF frames, I know that the color of the airbox is not an exact indicator or the model.  

Anyway, I had an extra 6B bottom end and wanted to rebuild this as a 100 but started looking through the spare parts manual (Page 11, Plate 8 Table) and I don't see reference to a 100CC (48MM bore) jug paired with a 6B bottom end.  I had always assumed that by 74 the Berkshire was using a 6B bottom end, but I am just not seeing it in the book.  Is the book just incomplete or am I looking to build something that never existed?   Conversely, if this did exist does anyone know of the correct part numbers for a 48MM jug and head for a 6B bottom end.

Thanks,

Kevin

[brian kirby]

Yes. Some early 72s had the 6A then from early 72 on to 74 they had 6Bs, 75 had the 6D. My 72 Berkshire has a 6B in it it and it was originally a 100, not a converted 125.

Brian

[KJDonovan]

Thanks Brian, so that being the case I am guessing the part numbers called out for 100/6A jug and head will work just fine on the 100/6B?

[brian kirby]

I think the top ends are the same, only the bottom end/crank is different between the A and B.

Brian

[Dale Fisher]

Note: The 6A alloy cylinder would typically (but not always) have fins cut for a side pipe.  A 6B or CMF alloy cylinder is full finned.  A 5A head will typically be full finned (but not always) and a 6B cut for the over the engine pipe.  It's fairly common for both the 100cc and 125cc heads to have the same part number in the casting.  Highly recommended to ask the dome size when shopping, cylinder is easily identified by the extra front and back conrod clearance notch in addition to the transfer cut outs.  Check the search topic feature for more information.

Dale Fisher
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