Author Topic: A7 conrod on A10 shaft  (Read 500 times)

Online Peter in Aus

  • Valued Contributor
  • ****
  • Join Date: Feb 2014
  • Posts: 327
  • Karma: 1
  • South West, West Australia
A7 conrod on A10 shaft
« on: 25.05. 2018 07:43 »
I have just scored a A10 crankcase (ZA10 129**) and shaft that had been sitting in a shed for many years, on pulling it apart the conrons where for a A7 (6in BC) the shaft is A10 (84mm stroke)
Has any one come across this before?*conf2*
I didn't get the barrel or pistons with it so am at a bit of a loss as to what is going on?
It was pretty obvious that it had been working like this, the shaft is in good condition the conrods where a bit of a problem, the PO that did them up had used lock-tight and when I tried to undo them the bolt turned in the conrod and stuffed it.
 Peter

Busselton West Australia
49 A7 longstroke
58 A10  SA

Offline BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 1985
  • Karma: 32
    • BSA National
Re: A7 conrod on A10 shaft
« Reply #1 on: 25.05. 2018 10:00 »
There was a "hot rod" set up, which I thought was a factory competition modification, but I am not quite so sure now.
It involves lopping one fin off the barrels and fitting a shorter ( 6" rod ).
The landlorg got a stack of A 10 spitfire engines and there was a short barrel amongst the pile.
Dug up a couple of articles about the short rod engines.
Bike Beesa
Trevor

Offline muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8180
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: A7 conrod on A10 shaft
« Reply #2 on: 25.05. 2018 10:53 »
I think Rocker Racer has done that to one of his rig (sidecar) motors.
I went the other way and used A10 rods (shortened by 2.5mm) in my A7SS racer to run T160 pistons.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: A7 conrod on A10 shaft
« Reply #3 on: 25.05. 2018 13:34 »

 When i was keeping my original Road Rocket alive in the '70's, I was told speedway guys used A10 cranks in Triumph engines in TQ race cars, so maybe they used short rods too.
  I wasted a lot of time chasing up stuff in that realm.

   That's what i was *told*...
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 Peter in Aus

  • Valued Contributor
  • ****
  • Join Date: Feb 2014
  • Posts: 327
  • Karma: 1
  • South West, West Australia
Re: A7 conrod on A10 shaft
« Reply #4 on: 26.05. 2018 01:33 »
Thanks all for the replies, looks like it is not that uncommon.
 *beer*
Peter

Busselton West Australia
49 A7 longstroke
58 A10  SA

Online JulianS

  • 1962 A10
  • Resident Legend
  • *****
  • Join Date: Mar 2017
  • Posts: 971
  • Karma: 20
Re: A7 conrod on A10 shaft
« Reply #5 on: 10.06. 2018 18:53 »
There was a US bulletin for fitting 6 inch A65 rods into a large journal A10, using A7 cylinder.

Also an article in "Motorcyclist" magazine in 1958.

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 5001
  • Karma: 48
Re: A7 conrod on A10 shaft
« Reply #6 on: 10.06. 2018 19:10 »
That is very intrresting, and one of the interesting points to notice is that they are serious about having the oil hole in the left con rod.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8180
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: A7 conrod on A10 shaft
« Reply #7 on: 10.06. 2018 21:35 »
G'dayJulian.
Thanks for that. The barrels would have been like the ones in another topic with thick flange and 1 less fin.
At those prices I'll have 10 please.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Peter in Aus

  • Valued Contributor
  • ****
  • Join Date: Feb 2014
  • Posts: 327
  • Karma: 1
  • South West, West Australia
Re: A7 conrod on A10 shaft
« Reply #8 on: 10.06. 2018 23:33 »
Thanks Julian, very interesting

At those prices I'll have 10 please.


And put me down for 2! *smiley4*

Busselton West Australia
49 A7 longstroke
58 A10  SA

Offline Klaus

  • Valued Contributor
  • ****
  • Join Date: Jun 2015
  • Posts: 367
  • Karma: 10
Re: A7 conrod on A10 shaft
« Reply #9 on: 11.06. 2018 05:53 »
Hi Guys,
this conversion is my current projekt.
But using A65 crank and shortend A10 thickflange barrel.
The driveside shaft can be easy cut   for the cushdrive.
Stroke is 74mm in compare with the 72,6 for the A7. With a std bore of 70mm give around 600 ccm.

cheers Klaus


If you think, everything is under control, you are not fast enought.