Author Topic: Plunger rear end  (Read 162 times)

Offline Degsy

  • A's Best Friend
  • ***
  • Join Date: Feb 2021
  • Posts: 36
  • Karma: 1
Plunger rear end
« on: 04.05. 2021 11:33 »
Putting the rear end back together (see photos below) can you spot which photo is wrong and no it is not the rear spindle missing.

Intuitively I thought well the slightly stronger spring must be on the bottom because the bottom spring will take all the weight. 

But the spring covers only go on one way and when I looked at them I thought they will fill up with water when it rains, that can’t be right. The penny dropped when I noticed I only had a maximum about 5mm travel before the tyre hits the mudguard and I realised the way the plunger works the load is taken by the top spring, so that is where the heavier spring goes.

It did not help that the old springs look wrong there is very little difference between the load bearing spring and rebound spring (see photo).  So decided to replace the springs.

New and old top spring (see photo) big difference, the new spring is longer and heavier.  Now they are in the correct position (left photo) with new springs I have enough suspension travel.

With these old springs on this bike the tyre must have been hitting the mudguard going over bumps.  Just another little surprise this bike rebuild has thrown up.

Degsy

Offline muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8761
  • Karma: 113
  • Lithgow NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Plunger rear end
« Reply #1 on: 04.05. 2021 12:53 »
Your lernin mate. LOL
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1467
  • Karma: 25
Re: Plunger rear end
« Reply #2 on: 04.05. 2021 18:14 »
 Degs.   Hard to tell if the originals are actually two correct pairs, all the same  or even the ones from this model.  There should be circular spring seats in the ensemble, adding extra length to the springs and making re-assembly a nail biting exercise without a homespun spring compressor. Hope yours weren't missing, you made it sound too easy. As we know now this bike is full of surprises reflecting the care and attention to detail of the previous owner.........

 Swarfy.

Offline Degsy

  • A's Best Friend
  • ***
  • Join Date: Feb 2021
  • Posts: 36
  • Karma: 1
Re: Plunger rear end
« Reply #3 on: 05.05. 2021 14:07 »
Swarfy - Yes it was not too difficult once I had home made a plunger column extraction and spring compression tool (see photo) out of some M10 studing and some big washers. 

Stripping the bike down the plunger columns were rusted in so I used two long impact driver sockets as drifts to push the plunger columns out.   

Compression and replacing the Springs does not need the sockets, once the springs are in place I can remove the studing and tap the trapped large washers out using another large washer and taping it out just far enough to get some pliers on the washer to pull it out, all the time being very careful not to displace the spring which could fly out and hit you in the face! (nail biting yes) because the plunger column is not in place at this stage to retain the spring.

Yes I did have the spring seats, although typically for this bike one seemed slightly different from the others and needed some filing down to fit on the end of the new spring.

Degsy