Author Topic: Primary drive Engine sprocket  (Read 1644 times)

Offline zitman

  • A's Best Friend
  • ***
  • Join Date: Feb 2009
  • Posts: 59
  • Karma: 0
Primary drive Engine sprocket
« on: 21.04. 2010 22:17 »
Hi all,

1959 A7SS.

I had my primary chain snap a few weeks ago, luckily just as I was moving off so no damage to anything else!

When I replaced the chain I upped the sprocket on the end of the crank to a 21 tooth from the standard 18 tooth.  The bike pulls it fine and revs much lower now.  I was just wondering if anyone else had done this?

Z

Offline LJ.

  • Peterborough UK.
  • Wise & Enlightened
  • *
  • Join Date: Jun 2006
  • Posts: 1403
  • Karma: 15
  • The Red A10!
    • LJ's Website!
Re: Primary drive Engine sprocket
« Reply #1 on: 21.04. 2010 23:27 »
Not very nice when a primary chain snaps! Mine went while travelling at 40 mph, happens so quick, huge bang then high revs, clutch in and brake to a halt.





Photos via Photobucket...
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline wilko

  • Resident Legend
  • *****
  • Join Date: Mar 2010
  • Posts: 681
  • Karma: 4
Re: Primary drive Engine sprocket
« Reply #2 on: 22.04. 2010 10:39 »
Thank the lord for pre-unit. Imagine if that happened to unit cases!!

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8237
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Primary drive Engine sprocket
« Reply #3 on: 22.04. 2010 13:06 »
Ouch, looks like the cush nut had come off once as well.
cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline zitman

  • A's Best Friend
  • ***
  • Join Date: Feb 2009
  • Posts: 59
  • Karma: 0
Re: Primary drive Engine sprocket
« Reply #4 on: 22.04. 2010 22:39 »
Looking at that I was lucky my went just as I was moving off.  Still embarassing though as it was the third weekend on the trot  I had failed to get where I was going!

Z

Offline BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 2004
  • Karma: 32
    • BSA National
Re: Primary drive Engine sprocket
« Reply #5 on: 26.04. 2010 10:17 »
As Musky noted, it looks like the cush drive nut has come loose.
This will allow the sprocket to move and can cause the chain to collapse due to too much side force on the side plates.
Did you fit a new lock washer under the cush drive nut ?
Bike Beesa
Trevor

Offline MikeN

  • A's Best Friend
  • ***
  • Join Date: Mar 2009
  • Posts: 220
  • Karma: 0
Re: Primary drive Engine sprocket
« Reply #6 on: 26.04. 2010 12:11 »
Thank the lord for pre-unit. Imagine if that happened to unit cases!!
I never new he designed it???

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8237
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Primary drive Engine sprocket
« Reply #7 on: 26.04. 2010 20:09 »
On the 8th day he created A7/10's.  *smile*
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Brian

  • Wise & Enlightened
  • *
  • Join Date: May 2007
  • Posts: 1706
  • Karma: 40
  • Mt Gambier, South Australia.
Re: Primary drive Engine sprocket
« Reply #8 on: 27.04. 2010 09:50 »
I reckon he created the A's on the first day Muskrat, then he went on to make all that other mundane unnecessary stuff. *smile* *smile* *smile*