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Gearbox bearing ...

  • 11 Jul 2015 12:55 PM
    Message # 3430361
    Anonymous

    I'm rebuilding my gearbox and cant find any information on which way round the radial/thrust 7207 bearing should be fitted ... can anyone advise ??


  • 12 Jul 2015 2:00 AM
    Reply # 3430774 on 3430361

    Hi.

    There is a cross section of the gearbox on page 10G in the RO.

    As I see it in the drawing, it has to resist the thrust from the chain sprocket side of the gearbox.

    In addition, the large nut inside the box would lock the bearing in place, bearing on the thrust side of the inner race of the bearing in question.

    Mike.

     

  • 12 Jul 2015 2:15 AM
    Reply # 3430776 on 3430361

    If you really are using a radial/thrust bearing, the clutch is pulling very hard on the bearing when you press down the pedal so the bearing must be turned the way it can take that. Open side of the outer race facing toward the inside of the transmission.

    I advice against a thrust bearing in favour of a common deep groove ball bearing because with a thrust bearing there is a relation between both sprocket and clutch side bearing. In order for a thrust bearing to function properly, it has to be kept within a precise pre-load or side play (.005-010" side play in the Indian gearbox). Too much side play and the up-and-down play in the thrust bearing becomes too large.

    The thin sprocket bearing is rather too weak for the tear and jerk the chain is producing and is not keeping its specified side play for any length of time. It'll work fine for a while but the sideplay becomes larger and larger. And when that happens the mainshaft sideplay doesn't stay within specs and the clutch bearing gets too much sideplay.

    With an excessive up-and-down play the clutch basket might, or likely, start to wobble or shudder with added noice and wear. A common deep groove ball bearing is not depending on the thin sprocket bearing as it has support in it self in both directions, thus maintains both lateral and axial play better. A deep groove bearing is not really engineered to take very high side thrust but experience has prooved it will endure the sidethrust that the clutch will produce, for a long time.

    Add to that there is a difference between the thrust bearing found original in the Indian and a new produced thrust bearing. The Indian original bearing can accept more side play than a new bearing before having too much up-down play because the race angle in relation to the balls are smaller, just maybe 15 degrees, than new bearings with 40 deg. slope. So don't be fooled when you find a new bearing with the same stock number 7207 or equivalent they really are constructed to be in pairs facing each other or/and have a set pre load.

    101 transm. can use a 6207 bearing without modification and I strongly recommend 6207 2Z that is double side rubber sealed. The bearing is lubed for life, far longer and harder life than in a Indian gearbox, and the sealings will shield from dirty gearbox oil soiled with metal flakes from the cogs and clutch debris.

    I haven't worked with the older gearboxes where the thrust bearing is mounted from the outside so I don't know what bearing will fit. I belive the dimension might be different than the 72x35x17 for a 6207, so it could require some modification to take a std bearing. Maybe just require to grind the bearing seat deeper in the clutch hub, plus a thicker thrust washer, but I don't know.



    Last modified: 13 Jul 2015 2:25 AM | Carl-Erik Renquist
  • 12 Jul 2015 5:51 AM
    Reply # 3430837 on 3430361
    Anonymous

    Thanks Charlie and Mike .... I looked at the cross section Mike and it shows the clutch side bearing being fitted from the outside of the box , my box requires the bearing to be fitted from the inside ... Charlie, I can understand what you are describing ... the 7207 bearing is pretty floppy and loose without a preload and I can imagine that if the geartrain settles in enough to allow a loss of this pressure on the inner race then the bearing is liable to chatter through its speed range ... I'm still not clear about which way round the 7207 should be fitted .... The Tech tip

    http://www.101scout.org/resources/Documents/101Association_TechTip01.pdf#zoom=100

    says to have the open face of the race to the inside of the box ... Is this correct ???  Thanks again for the knowledgable advice ....

  • 12 Jul 2015 6:06 AM
    Reply # 3430840 on 3430361
    Anonymous

    Sorry ... I just noticed you confirmed that the thrust must be on the outside of the box to take the clutch load ... thanks Charlie ....

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