The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: melvyn on 10.05. 2010 18:11

Title: Engine sprocket 23t
Post by: melvyn on 10.05. 2010 18:11
Hi Chaps can you help. I found out that my 59 A10 was fitted with a sidecar sprocket ,so ordered a 21t solo sprocket & new primary chain-reassembled etc, to find the primary chain was to short. After further investigation (Thanks Ted) that I had been sent a 23t sprocket.Any thoughts on gearing etc.! Should I lengthen the primery chain or replace the engine sprocket with the correct 21t.Thanks Melv
Title: Re: Engine sprocket 23t
Post by: Beezageezauk on 10.05. 2010 19:08
Hi Melvyn,

You will probably find the 23 tooth engine sprocket too high for your bike.  I believe that this size was only used on the Rocket Gold Star models and they had the extra power to accommodate it.

On a personal note I've found the standard 21 tooth sprocket makes the A10 quite revvy but ideal for riding round the country lanes.  If this is how you use your bike go for your original idea of using 21 teeth.  However, if you often use the dual carriageways and/or motorways I would suggest that you try a 22 tooth sprocket.  This would give you a higher cruising speed but at the expense of swift acceleration.  This is the sprocket that I use.  It gives me both options and my A10GF copes with it ok.

Title: Re: Engine sprocket 23t
Post by: melvyn on 10.05. 2010 19:43
Thanks for the info much appricated Regards Melv
Title: Re: Engine sprocket 23t
Post by: RichardL on 10.05. 2010 20:28

I just changed from a 21 to a 22 and have found the results as Beezageezauk describe. With the 21 it was uncomfortable staying in the high 30's in 3rd gear for typical driving on surface streets. It made for a lot of shifting to 4th when trying to get just a bit faster and then soon needing to downshift on the slightest speed reduction (many of the surface streets where I live are posted 40 MPH). Actually, when I was looking for a new sprocket, I was looking for a 23, but a 22 popped up on eBay, so I decided to try that. Considering what B'g'uk has said, and my increased riding comfort, I guess I made the correct choice, but I only have about 65 miles on the 22, so far.  

Richard L.


I looked at your band website and watched parts of the videos. The band seems like a lot of fun and, by the way, I live in the Chicago area. Also, once-upon-a-time, I played bass (not that well).  
Title: Re: Engine sprocket 23t
Post by: melvyn on 10.05. 2010 23:56
Thanks Manosound did you have to lengthen the primary chain to accomodate the larger sprocket?-- As far as the band is concerned,yes a lot of fun.I need to get to Chicago and have a fix of Blues Cheers Melv. ps your never to old to pick up that bass again!!!
Title: Re: Engine sprocket 23t
Post by: RichardL on 11.05. 2010 12:05
Melvyn (and Beezageezauk),

In my previous comments, I forgot to factor in the fact that my gearbox is an "Sc" scrambles. At 2.344:1 in first, versus an "Std" at 2.581:1, the 23 would have been an bit luggy off the line. On the other hand, it seems to me that the higher ratio of the the "Sc" versus the "Std" would have made the 23 better in 3rd, but not enough so to offset the situation in 1st. If that explanation seems like I'm on the edge of knowing what I'm talking about, it's because I haven't really given the whole question much thought before, and this is the only bike I own.

Richard L. 
Title: Re: Engine sprocket 23t
Post by: chaterlea25 on 15.05. 2010 22:00
Hi All,
I have been running a 23 tooth engine sprocket (as discussed on the forum before, do a search!!)
I have had no issues with it and a std box, but then again I have a SR!!
John O R