Help needed with BA gearbox rebuild

[T.J.Falloon]

Hey again all,

I was hoping that the brains trust here would be able to help me to either confirm my suspicions or point me in the right direction with a BA gearbox rebuild.
I am presently in the process of rebuilding a BA gearbox for a mate of mine, I believe it may be eventually going into a 600 SQ4, not 100% sure.
Anyway when I received the gearbox , it came to me in pieces and with a number of various gears , shafts, gear clusters, etc.
I have managed to sort what I think are the appropriate gears ( using Draganflys parts list etc ) and selectors. There are no identifying numbers on the cases other than what are in the photos (see attached ).

My problem is that the clutch shaft ( output shaft ) does not appear to be the right shaft, to me when I check the Draganfly parts lists, it looks like the output shaft for a GB gearbox and not a BA.

Is anyone out there able to confirm or point me in the right direction.

Thanks once again for your help.

Cheers.

T.J

[Vincent.vanGinneke]

A GB shaft, as can be seen in Drags list, has a removable clutch spline bit 3766-52 (or whats the name)
The CP and BA shafts have this fixed to the shaft.
I will have to look in my parts bin before I can tell you if the shaft you have is a CP or BA.
It could be a CP shaft.....

[T.J.Falloon]

Thanks Vincent, appreciate your assistance.

[Pete.Silson]

The picture looks to me like a post 1948 mainshaft (longer clutch centre splines). The SQ4 BA mainshaft is longer (303mm) than for BA singles (294mm). I can't really make out the length from your picture but it looks to be less than 300mm so you may have a mainshaft from a single. Using a shorter mainshaft on a SQ4 causes misalignment of the primary drive/clutch.

I believe the 600 SQ4 used a CP box and (being prewar) had the shorter clutch splines. Using a later BA gearbox works but it must have the correct shaft length and will need a later long spline clutch centre to go with the mainshaft.

Pete

[john.whiting]

A BA shaft id is 23.7mm dia approx directly behind the clutch mounting (ie Inside the sleeve gear)....a CP shaft is considerably smaller diameter.......The shaft shown with the tape measure is an Ariel shaft.......the one in the diagram is not,rather it is the Matchless/Panther ,etc type......The Ariel 38 on clutch is unique in having a wide needle roller bearing support ,instead of a 1/4x1/4 roller bearing and thrust bearings that is typical Burman.

[Vincent.vanGinneke]

Top one is a CP shaft.
Bottom a BA shaft

[paul.jameson]

Your gearbox case is for a Square Four. The mountings are offset for the Square in comparison to those of the single.

[T.J.Falloon]

Thank you everyone for your help. I appreciate it.

[Alan G]

Top one is a CP shaft.
Bottom a BA shaft

IMG_7324.JPG

Can anyone tell me the thread size on the right hand (kick start) end of these shafts? My VH has damaged threads I need to clean up to get the nut on. They are not terrible, but are damaged by the wrong nut being forced on, so the correct nut will not go on square.

[Roger Gwynn]

Copy of post earlier this morning on 'VH Clutch'

Virtually all fine threads on 4 strokes are Whitworth Fine almost always 26 tpi up to and including 7/16 and 20 above. There are a few BSF threads and a few finer threads on larger sizes. This includes Burman parts but not Lucas or Amal. CEI is usually quoted but most works drawings do not specify, only giving diameter and pitch, when a thread is stated it is usually Whitworth, occasionally CEI so I think they were a little confused.