Author Topic: A10 timing gears A7 Longstroke timing gears mixup (solved)  (Read 707 times)

Offline beezermacc

  • Resident Legend
  • *****
  • Join Date: Dec 2011
  • Posts: 994
  • Karma: 39
  • Not for the purist!
    • Priory Magnetos Ltd.
I was round at a mate's house at the weekend. He'd just rebuilt his A10 engine. Whilst doing so he'd changed a couple of the timing gears for ones in better condition. Mistake! In spite of everybody's best efforts the bike wouldn't start. A few pops in the exhaust was the best result. After a bit of head scratching we decided to put the original gears back as this was the only significant change made during the rebuild. Hey presto! the bike strted second kick and sounded fine. Having some knowledge of A7 longstrokes I was aware that the gears are different but didn't think my mate had any A7LS bits in his collection. I though it worthwhile to do some pictures. If I'm building an engine I always check the timing gears. Here's the pics, they're on the Tech tips page of our club website http://www.cheshirebsa.co.uk/
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline bikerjohndavies

  • John Davies, Bath, UK
  • A's Best Friend
  • ***
  • Join Date: Jun 2010
  • Posts: 229
  • Karma: 3
  • 1953 BSA A10 Super Flash Project
Yep, the timing marks are a different number of teeth apart. The long stroke A7 is 16 teeth between the crank shaft pinion mark and the cam shaft one whilst the later short stroke A7 and A10 one is 20.
1937 Panther M100 Rigid, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10SF (WIP), 1954 Ariel VH, 1961 Triumph T120R

Offline beezermacc

  • Resident Legend
  • *****
  • Join Date: Dec 2011
  • Posts: 994
  • Karma: 39
  • Not for the purist!
    • Priory Magnetos Ltd.
Yep, the timing marks are a different number of teeth apart. The long stroke A7 is 16 teeth between the crank shaft pinion mark and the cam shaft one whilst the later short stroke A7 and A10 one is 20.
....all the gears are different actually!
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk