Author Topic: Loose Sprocket  (Read 665 times)

Online cyclobutch

  • Wise & Enlightened
  • *
  • Join Date: Aug 2010
  • Posts: 1510
  • Karma: 14
Loose Sprocket
« on: 03.03. 2014 09:58 »
Rolling my Bitza in and out of the garage at the weekend - it's the only mileage it's been doing since around October time; I noticed a dragging noise off the back some where. Investigation revealed the chain rubbing at the front of the rear mudguard ... intermittently. Further investigation showed the rear sprocket holding bolts to be loose. I have a QD wheel fitted.

Eek, and out with the spanners. BSW/BSF, no decent fit. AF same. Metric? No, but this is the nearest. What spanners should I require for these bolt heads? 
Various, including ...
'58 Iron Head Flash Bitza


Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Loose Sprocket
« Reply #1 on: 03.03. 2014 11:11 »

 Do you mean a chainwheel with a replaceable sprocket band, with about 10 or 12 short  bolts?
   Sounds like a A65/50 one, I have one with socket cap screws so can't help with spanner size-  could be UNF threads from memory, bsf at a stretch, have you measured them across flats....? possibly factory specials
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online cyclobutch

  • Wise & Enlightened
  • *
  • Join Date: Aug 2010
  • Posts: 1510
  • Karma: 14
Re: Loose Sprocket
« Reply #2 on: 03.03. 2014 12:39 »
Nah. Its a dished type sprocket - not stamped out; forged maybe? Just four retaining bolts. Measuring up I'm getting somewhere around 13.65 - 13.80 mm AF. Switching that to an imperial AF size would somewhere around 17/32" (13.49) to 35/64" (13.89 mm). I'm unsure what the AF sizes actually are on BSF/BSW spanners?

I just about got enough grip with a 14mm, but it clearly ain't right. 
Various, including ...
'58 Iron Head Flash Bitza


Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Loose Sprocket
« Reply #3 on: 03.03. 2014 13:06 »

1/4 ww is smaller, I'd say most likely then, but that sprocket is not in my league, sorry
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline trevinoz

  • Newcastle, N.S.W. Australia.
  • Wise & Enlightened
  • *
  • Join Date: Jul 2006
  • Posts: 2903
  • Karma: 67
Re: Loose Sprocket
« Reply #4 on: 03.03. 2014 21:52 »
I think that a 5/16" BS hex is 0.520" which sounds awfully close to what you have.

Trev.