The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: bikerjohndavies on 14.07. 2015 08:46

Title: Difference between early and later timed breather
Post by: bikerjohndavies on 14.07. 2015 08:46
I was wondering if somebody could tell me the difference between the early timed breather part number 67-130 and the later one 67-987?
Title: Re: Difference between early and later timed breather
Post by: bikerjohndavies on 23.07. 2015 08:07
Somebody must know what the difference is between the 2 different part numbers, if any.
Title: Re: Difference between early and later timed breather
Post by: bsa-bill on 23.07. 2015 08:17
think I read some where the peg is not in the same place  (relative to the keyway) but I've no personal knowledge
Title: Re: Difference between early and later timed breather
Post by: bikerjohndavies on 23.07. 2015 08:30
Thanks Bill, Yes the peg on the early long stroke cam pinion is at the 12 o'clock position compared to the keyway while on the later short stroke motors its at 1 o'clock. That made me think that the timed breather must also be different otherwise the breather hole would be open at a different part of the stroke. Cheers, John
Title: Re: Difference between early and later timed breather
Post by: duTch on 23.07. 2015 08:57

 All I know is I think my Plunger one is a different shape/profile on the top/outer end of what I remember my R.Rocket had... *dunno2*..... other than that  *dunno*
Title: Re: Difference between early and later timed breather
Post by: trevinoz on 25.07. 2015 02:20
BikerJohn,
                        The difference in the breathers is the early 67-130 is waisted on the outer end and the 67-987 is tapered.
67-130 was fitted to both long stroke and short stroke engines.
I think that the change of form was for 1953 when quite a few mods were made.
I can't see why they couldn't be interchanged with each other if the correct one for the year wasn't available.
The holes appear to be in the same position on both types.
Title: Re: Difference between early and later timed breather
Post by: bikerjohndavies on 25.07. 2015 07:55
Hi trevinoz, thanks for the reply. That explains it but as you say the holes are in the same place on both versions whilst the long stroke cam pinion has the peg at 12 o'clock while the short stroke is a 1 o'clock so the breathing timing on the long stroke must be slightly different. That is unless the keyway on the cam shaft is in a different position. The joys of classic bikes.