The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Klaus on 08.09. 2015 08:57

Title: Big journal conrod
Post by: Klaus on 08.09. 2015 08:57
Hi gents, does anybody know the diameter with toleances of the bore from a big journal conrod? I mean the bore without the shells.
Hayns tell the figures  for conneting rod big-end eye diameter 1.4610 - 1.4615 inch. But it is for small journal.

cheers Klaus
Title: Re: Big journal conrod
Post by: Viking on 09.09. 2015 12:15
I think the answer is here:

https://groups.yahoo.com/neo/groups/bsa/conversations/topics/13582

BSA service sheet No. 207, October 1948, re-printed May 1955.
 
Engine nos. XA7 - 101 to 600; first re-grind 1.4600 to 1.4595, with a
 0.065/0.060 face radius both sides. No second re-grind.
 Engine nos. XA7 601 upwards and A10 models; three re-grind possibilities.
 1.4495 to 1.4500; then 1.4400 to 1.4395; then 1.4300 to 1.4295.
 More information from that service sheet; Note that certain engines will be
 found to have the left-hand connecting rod drilled to improve lubrication
 ......
 

BSA service sheet No. 207, October 1948, revised January 1958.
 
As above, but also data for the large journal crankshaft;
 1.677/1.6765 with 0.120/0.115 face radius; 1.667/1.6665; and 1.657/1.6565
 (10, 20 & 30 thou undersizes).
 
 
Title: Re: Big journal conrod
Post by: duTch on 09.09. 2015 12:48

 I don't think that's correct, going on those engine numbers for starters, and unless I'm reading it wrong they're small journal regrind sizes anyway...I'm fairly sure I have that noted somewhere, give me ten minutes or so...
   
Quote
I mean the bore without the shells.


 edit- Ten minutes or so later...can't find the exact info just now, but measured a couple of old rods and they're in the vicinity of 1.8425"...notebook'll be in the last place I left it.

 I bought new rods and have the specs on them somewhere too.