Author Topic: engine sprocket  (Read 859 times)

Offline baz

  • A's Best Friend
  • ***
  • Join Date: Apr 2012
  • Posts: 56
  • Karma: 2
engine sprocket
« on: 06.09. 2018 18:28 »
does anyone know where to buy a decent quality 23 0r 24 tooth two lobe engine sprocket? preferably in the UK
i recently bought a wassel 23 tooth sprocket  and it was so thick the cush drive would not work and it projected out too far to get the chain alignment to the clutch
so i ran a file over it and found the thrust face to be soft,so i put it in my lathe to machine some material from the back then i realised the centre of the sprocket was bored offset so i sent it back
i'd like to know where i could buy one that just fits cheers

Offline a

  • Valued Contributor
  • ****
  • Join Date: Feb 2011
  • Posts: 273
  • Karma: 4
Re: engine sprocket
« Reply #1 on: 07.09. 2018 01:19 »
Hi Baz,
We have them here in stock, 2 lobe 24 Tooth Genuine BSA NOS.
https://mikesclassiccyclespares.com/product/45-2775/

Offline baz

  • A's Best Friend
  • ***
  • Join Date: Apr 2012
  • Posts: 56
  • Karma: 2
Re: engine sprocket
« Reply #2 on: 10.09. 2018 17:29 »
ok thanks for that ,all i have to do now is decide if a 24 engine sprocket will over gear my bike too much?? regards baz

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3257
  • Karma: 47
Re: engine sprocket
« Reply #3 on: 11.09. 2018 01:10 »
Hi Baz,
That depends on the state of tune of the engine and rider weight
I have tried 23 and 24 tooth on my SR
24 was a bit high riding 2 up
I put in a 23 when I went touring in the Alps
and have stuck with that since

John
1961 Super Rocket
1963 RGS (ongoing)

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5454
  • Karma: 62
Re: engine sprocket
« Reply #4 on: 11.09. 2018 10:30 »
Quote
ok thanks for that ,all i have to do now is decide if a 24 engine sprocket will over gear my bike too much??


I went the other way, not looking for top sped but a bit more oomph of the mark but not wanting to go to sidecar ratio.

I got what I wanted by changing engine sprocket and gearbox sprocket to get something in between
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online BigJim

  • Valued Contributor
  • ****
  • Join Date: Aug 2018
  • Posts: 303
  • Karma: 1
  • Bristol. UK
Re: engine sprocket
« Reply #5 on: 11.09. 2018 11:27 »
I got what I wanted by changing engine sprocket and gearbox sprocket to get something in between

Hi Bill, What are you running and where did you get the bits?
Jamie,  Supporter of Distinguished Gentleman's Ride

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5454
  • Karma: 62
Re: engine sprocket
« Reply #6 on: 11.09. 2018 11:50 »
Quote
Hi Bill, What are you running and where did you get the bits?


the bits were for my RGF ( Rocket Gold Flash) Flash engine with alloy head and 375 cam and rocket carb, was a good ides that didn't quite turm out as I'd hoped, goes well enough and turns good but looks looks heavy and a bit ugly if I'm honest, was a lot of fun to do.

I' m in the shed today so I'll see if I can find receipts, would be the usual sources I'd imagine
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online BigJim

  • Valued Contributor
  • ****
  • Join Date: Aug 2018
  • Posts: 303
  • Karma: 1
  • Bristol. UK
Re: engine sprocket
« Reply #7 on: 11.09. 2018 14:03 »
Sorry for my inept questioning Bill. What i meant to ask was what nr teeth on engine and gearbox runs well for you?
Jamie,  Supporter of Distinguished Gentleman's Ride

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5454
  • Karma: 62
Re: engine sprocket
« Reply #8 on: 11.09. 2018 14:58 »
oh I see - now cant go to memory so it's rummage in the shed again
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5454
  • Karma: 62
Re: engine sprocket
« Reply #9 on: 11.09. 2018 17:04 »
Quote
Hi Bill, What are you running and where did you get the bits?


right after looking through a box of receipts I'm heart broken ( burn the damn things ) and even more confused as I found in my engine spares drawer an engine sprocket and two gearbox sprockets also had two receipts from C&D Autos .

So looks like I went for a slight reduction gearwise a 22 tooth on the engine and 18 (sidecar) or 19 on the gearbox, but why are they in the drawer, well I think due to the problems I had starting the beast I decided to revert to standard gearing ( I know silly thinking but I was getting pretty desperate for explanations).

Remember that this was to slightly reduce overall gearing where as you want to go in the other direction, I remember using a gear ratio page from this forum I think, try a search here for Gear ratio and you might get it
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Online berger

  • Wise & Enlightened
  • *
  • Join Date: Nov 2017
  • Posts: 1142
  • Karma: 7
  • keith.chesterfield uk 500sscafe.norbsa project
Re: engine sprocket
« Reply #10 on: 11.09. 2018 21:37 »
baz I've got two 24 tooth , one used one nos- I will find them tomorrow and measure some measurements and post on here sometime in the afternoon. I might still have a 23 I tried on my 500 but it was too tall so I took it off many years ago carn't remember what happened to that one so I will have a butchers tmow . I had a problem with a gearbox sprocket I bought in the 80s that was all over the shop when put in the lathe--- no wonder I couldn't adjust the chain -  *bash* *rant*

Offline worntorn

  • Valued Contributor
  • ****
  • Join Date: Jun 2015
  • Posts: 376
  • Karma: 2
Re: engine sprocket
« Reply #11 on: 12.09. 2018 04:11 »
I suspect a 24 tooth will be too tall.
The higher horsepower rating of the higher tuned models is of little help here as that extra power is all above 5000 where these old beauties rarely go.
Power up to 5 k is about the same for all versions of the A10, give or take a couple of horsepower.
The lower tuned bikes might even have a slight advantage in grunt up to 5 k , which would help in dealing with overgearing.
I have a 23 tooth on my 63 SR and it is OK, however if I  reduce the vibes via dynamic crank balance this winter, the stock 21 tooth is going back on. It definitely pulled better in every gear with the 21 tooth on there.
Basic Physics tells us that there is  9.5 % more torque at the rear wheel in each gear with the stock 21 tooth engine  sprocket vs. the 23 tooth. The 21 gives 14.6 % more torque than the 24 tooth.

Glen

Online berger

  • Wise & Enlightened
  • *
  • Join Date: Nov 2017
  • Posts: 1142
  • Karma: 7
  • keith.chesterfield uk 500sscafe.norbsa project
Re: engine sprocket
« Reply #12 on: 12.09. 2018 11:16 »
 I agree about the 24 tooth worntorn its a big gear more suited to the RGS and tuned variants, I have now found my slightly tuned shooting star engine is happy with a 22 engine and 19 gearbox without over working the clutch and she sits nicely at 50mph at 2500 revs. before I played about with this set up she was running 21 engine and 20 gearbox and knew she wouldn't like 22 engine and 20 gearbox so luckily the swap turned out nicely

Offline worntorn

  • Valued Contributor
  • ****
  • Join Date: Jun 2015
  • Posts: 376
  • Karma: 2
Re: engine sprocket
« Reply #13 on: 12.09. 2018 14:20 »
I'm pretty sure the RGS has exactly the same engine as my 63 SR, 9 to one CR and 357 cam.
 I don't see it doing any better with a 24 tooth than this SR would.
From Orabanda's dyno results, the lower tuned bikes actually showed a teensy bit more grunt 3k to 5 k than the HHC motor. I think the higher tuned bikes like mine are, if anything, less suited to overgearing. They need to rev to get that extra power and the overgearing goes against that.
Now I'm just going by my own results with this single bike and by the numbers, but I think the idea of a much more powerful version on the A10 engine in the RGS is a bit of a myth.

Berger, with your Shooting Star, what is your new overall ratio vs old?

Glen

Online JulianS

  • 1962 A10
  • Wise & Enlightened
  • *
  • Join Date: Mar 2017
  • Posts: 1006
  • Karma: 20
Re: engine sprocket
« Reply #14 on: 12.09. 2018 14:35 »
Remember that although the RGS ran a larger engine sprocket (23 teeth) than the SR (21 teeth), as standard, it also had lower gearing gearbox to rear wheel. SR and RGS both had 19 tooth gearbox sprocket as standard, SR had 42 teeth rear sprocket and the RGS 46 teeth.