Author Topic: Zero end float on A7SS crank, a problem?  (Read 198 times)

Offline Peter Gee

  • Valued Contributor
  • ****
  • Join Date: Apr 2015
  • Posts: 268
  • Karma: 1
Zero end float on A7SS crank, a problem?
« on: 12.09. 2018 20:29 »
Just about ( under extreme pressure of time for an international  show) to bolt up the cases of my 59 A7SS. I know this matter has been often gone over.

The engine as I got it had never been taken apart or was at least standard in all bearings and had three shims fitted...but  giving end float with a  noticeable ( buy hand) CLUNK.  Was hard to measure on the equipment I have.

I've tried a dozen  shim combos on rebuild  and got either CLUNKS or crank stiffness or binding  with the drive spring and etc fully assembled. Sometimes I got no stiffness when the engine was vertical or laid on DRIVE side, but stiffness to some degree if laid on TIMING side..even with the drive nut done up.. I figured that was no good.

Finally I found a single shim  0.014" from a pack I have gives no discernable end float or one I can measure without going to a machine shop, and  no hint of a clunk..but it gives free rotation of the crank with the drive fully done up to 65 ft lbs..EVEN if I  lay the engine  on the timing side. However if I put in a 0.016" shim, CLUNK!

Am I good to go with 0.014" "zero discernible float"  shim ? After all there must be some clearance I can't measure with my equipment, otherwise the crank would bind or stiffen as previously.  It's confusing. Nicholson recommends up to .0008 end float ,   Haynes  no more than  0.003" and the factory 0.001~0.003".

I did follow Muskrat's procedure he kindly sent. Why on earth BSA did not change to to ball from a roller, as Triumph did, is beyond me. Help welcome.

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 7979
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Zero end float on A7SS crank, a problem?
« Reply #1 on: 12.09. 2018 21:10 »
G'day Peter.
A couple of thou is hard to feel. Did you try 12 and 13? If the crank turns freely with the 14 with no feeling of end float I'd go with it. End float increases as the motor gets hot.
A rough way to measure the end float is with feeler gauges between the crank and case web through the top.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Peter Gee

  • Valued Contributor
  • ****
  • Join Date: Apr 2015
  • Posts: 268
  • Karma: 1
Re: Zero end float on A7SS crank, a problem?
« Reply #2 on: 12.09. 2018 21:18 »
Dear Muskrat, you are so always helpful. Yes I think it's good to go because (a) I will be pootling  not flogging the engine until at least 500 plus miles (b) I thought of the fact the alloy cases will surely expand more than the iron crank.

People could argue about this forever. I tried 0.0012" and got..CLUNK! Obviously the head and blockwas not on so sound travels..still I have  read enough posts on hear about the dreaded CLUNK to be delighted I heard none yet got free spin.

Is there a ball conversion for the DS?  Triumph did it!

Online trevinoz

  • Newcastle, N.S.W. Australia.
  • Wise & Enlightened
  • *
  • Join Date: Jul 2006
  • Posts: 2839
  • Karma: 66
Re: Zero end float on A7SS crank, a problem?
« Reply #3 on: 12.09. 2018 22:24 »
All of the modern Triumph engines that I have seen have a roller on the drive side.
The long stroke A7 has a ball bearing on the drive side so it should be quite possible to do the same to your bike.