REAR SPROCKET

[panman]

Hi , Is there a selection of rear sprocket sizes available for 1963 A65 Star, 4 bolt fitting type 

[limeyrob]

I'm only aware of 4206331 (42T) and 68-6034 (43T)
The usual changes to drive ratio are on the engine sprocket or the gearbox sprocket.

[panman]

I have a 42T rear sprocket but feel it could be geared up I'll have to check the engine and gearbox ones then see what's available

[limeyrob]

I raised the gearing on my A65, made it much nicer to ride and moved the vibration out of the normal range.  I fitted the biggest gearbox sprocket I could get, I think its 22T, this is the easiest way to up the gearing.  Mine was a late model and the case was cut behind the clutch so the 22T would fit. I don't know if this was standard on all A65s, someone will know or call SRM as they sell the 22T sprocket.

[panman]

Ive checked mine 20t gearbox and 43t rear sprocket, was there a standard fitment when leaving the factory?

[limeyrob]

I think standard is 20 / 42. Depending on where you ride you may find the standard gearing a bit low. Fine in town and in hilly / country lanes but on A roads and motorways you will want a higher gear.
When your bike was sold in 63 only about half of the M1 was open and there was no other motorway. A roads (trunk roads) were often 3 lane not dual carriageway so there was a lot less need for a high cruising gear.
US export models were geared for a fast 1/4 mile so even lower gearing.

[DAVE BRADY]

Hi,

I went up one tooth on the gearbox on a '51 Flash and an A65. It was enough to reduce the business of the engines at cruising speeds but did not compromise lower speed riding.  Many miles and a great variety of terrain ridden covered and very suitable for both bikes.

Dave.

[panman]

Thanks guys i'll leave it for the summer and change it in the winter time