Author Topic: rod journal diameter?????  (Read 513 times)

Online jachenbach

  • Resident Legend
  • *****
  • Join Date: Feb 2014
  • Posts: 562
  • Karma: 8
rod journal diameter?????
« on: 08.02. 2015 01:17 »
Been going crazy trying to find a spec that makes sense for rod bearing journals. By the numbers in Haynes and the chart found in a service sheet on this forum, and the service sheet on regrinding crankshafts, it would seem they start at 1.45 inches. I've measured 5 of them that I've had here. 4 of them measured 1.66 with a caliper. The one for the Spitfire (that I intend to use) measured 1.68 with the calipers. I got the Starrett micrometers out and measured both journals and got 1.686 inches both journals nice and concentric. I'm guessing this crank may be original size and others were reground .020 undersize, but why can't I find this info anywhere???? After looking it over more closely, I'd like to at least get it polished and put fresh bearings in, but without the starting size I don't know what bearing to order.

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8027
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: rod journal diameter?????
« Reply #1 on: 08.02. 2015 02:17 »
G'day jachenback.
A7 (short stroke) and small journal A10 are 1.460". Large journal A10 are 1.687".
http://www.srmclassicbikes.com/technical/bsa-a7-a10-big-end-journal-sizes
Not sure about the long stroke A7's.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline terryk

  • Valued Contributor
  • ****
  • Join Date: Oct 2006
  • Posts: 455
  • Karma: 3
  • Townsville Queensland Australia
Re: rod journal diameter?????
« Reply #2 on: 10.02. 2015 13:44 »
Longstroke same as short stroke
1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm