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Dan

Bevel gear setup

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Hello Pete Roper,

  I have a few questions about rebuilding a rear drive. Can you help? Or Would you be willing to give some advice I should have said!

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What do you need to do? Replace a seal? A bearing? Or the whole CW&P assembly?

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Hello Pete! or maybe G'day mate?

Well I am a racer (big deal I know) and it is a 1975 850T based machine. I have replaced the 8/37 bevel gears with 7/33

as they are more readily available and reasonably priced from Stein Deinse. Anyway this whole shootin match is going into

a drum brake case, and the physical dimensions of the crown and pinion are literally smaller. Having said that, I and am reasonably aware of all of

the "tasks" that must be adhered to during the building process. i.e. backlash settings, pinion bearing preload, pinion crown gear mating position (to begin) and the optimum

POC on the pinion or crown. Having said that, do you realize that your technique for shimming is the opposite of the works manuals? Or maybe I am

reading that incorrectly? I am having a @#!#$# of time getting this fucking meshing growl out of the driving direction! Spin the wheel backwards, silent. But

not the "other "way! And that is after I have .0045 to.0059 backlash and a pretty good POC! Any advice from you would a treat! I am stumped or just plain dumb!

Regards, Dan Coyle #459 USCRA

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12 hours ago, Dan said:

Hello Pete! or maybe G'day mate?

Well I am a racer (big deal I know) and it is a 1975 850T based machine. I have replaced the 8/37 bevel gears with 7/33

as they are more readily available and reasonably priced from Stein Deinse. Anyway this whole shootin match is going into

a drum brake case, and the physical dimensions of the crown and pinion are literally smaller. Having said that, I and am reasonably aware of all of

the "tasks" that must be adhered to during the building process. i.e. backlash settings, pinion bearing preload, pinion crown gear mating position (to begin) and the optimum

POC on the pinion or crown. Having said that, do you realize that your technique for shimming is the opposite of the works manuals? Or maybe I am

reading that incorrectly? I am having a @#!#$# of time getting this fucking meshing growl out of the driving direction! Spin the wheel backwards, silent. But

not the "other "way! And that is after I have .0045 to.0059 backlash and a pretty good POC! Any advice from you would a treat! I am stumped or just plain dumb!

Regards, Dan Coyle #459 USCRA

If you are spinning the crown wheel in a backwards or what would be a reverse direction (not via the pinion shaft but by driving the crown wheel or back wheel itself) you are in fact loading the driving faces of the gears. If you spin the crown wheel in a forward direction you are loading up the back face or overrun side of the gears. So in fact the driving direction of the gear set when driven by the engine/transmission in your case will be silent.

Is this how you are driving the gear set or do you mean fwd and reverse via the input shaft.

Hopefully Pete Roper will chime in and I haven't confused the issue.

Ciao 

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Hello, Well now I am confused even more! After mounting the rear wheel, I am simply spinning said wheel in a forward 

i.e. driving direction. There is where the whirring sound will begin. The reverse direction is silent. Why? Backlash is nearly perfect 

and the POC is spot on!

 

 

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Are you sure it's the bevelbox and not the UJ support bearing or gearbox output shaft bearing?

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1 hour ago, Dan said:

Hello, Well now I am confused even more! After mounting the rear wheel, I am simply spinning said wheel in a forward 

i.e. driving direction. There is where the whirring sound will begin. The reverse direction is silent. Why? Backlash is nearly perfect 

and the POC is spot on!

 

 

Ok so spinning the back wheel in a forward direction isn't the same for the bevel gears as under throttle in the forward direction. Its not loading the gears in the direction that is normal for transmitting engine power, its operating the gears on the back faces in the overrun condition. I dont know if this whirring is normal in that overrun condition and my bike is in pieces and I cant check it but it seems to me that its more important to have the smooth operation under power than on the overrun as you have.

Ciao

  

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26 minutes ago, pete roper said:

Are you sure it's the bevelbox and not the UJ support bearing or gearbox output shaft bearing?

Do they normally operate smoothly in both directions Pete or is this a case of doing something thats not normally done and highlighted a normal condition that isn't normally noticed?

Wouldnt surprise me if Guzzi concentrated the grinding and lapping precision on the drive side of the gears only and the overrun faces are just what they are.

Ciao 

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Hello Pete,

 Thank you for the response. I am reasonably sure that both of those bearings are functioning as normal. Having said that,

removing the swinging arm assembly to have quick peek might be the prudent thing to do. But just for "shits and giggles" sake

if everything is kosher,  what gives man?

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On 3/5/2020 at 10:12 AM, Dan said:

Hello Pete,

 Thank you for the response. I am reasonably sure that both of those bearings are functioning as normal. Having said that,

removing the swinging arm assembly to have quick peek might be the prudent thing to do. But just for "shits and giggles" sake

if everything is kosher,  what gives man?

Any outcome here? For the sake of adding to the general knowledge base?

Ciao 

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