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Motor Sprocket (Tapered) Question

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rozemab
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Motor Sprocket (Tapered) Question

#1

Post by rozemab » Fri Oct 26, 2012 1:25 am

Switched out my 22t for a 23t motor sprocket and replaced the chain. The problem is I don't remember if the threads from the crank shaft extended beyond the sprocket nut. Visual inspection shows the sprocket is fully seated on the taper, with ~ 1/8in of the key protruding from the back of the sprocket.

1) Should the crank threads protude from the nut?

Visually, the sprocket runs true with the shaft when kicking the bike. (no 'wobble', or canted on the taper)

I do notice there is a slight offset of the primary chain at the sprocket ( half a link distance out, or port size of the bike). In other words, it does not appear like the primary chain is parallel to the mating surface of the tin primary. At the clutch, the links are fully under the tin; at the sprocket, it ~ 1/2 link width protruding out.

It does look like the chain at both sprockets is in the same vertical plane.

Is there something wrong with my assembly? I want it right, and I will fix it if it is not!
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Re: Motor Sprocket (Tapered) Question

#2

Post by UPSROD » Fri Oct 26, 2012 2:08 am

I have never seen a 58 with a tapered sprocket shaft.

rozemab
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Re: Motor Sprocket (Tapered) Question

#3

Post by rozemab » Fri Oct 26, 2012 2:23 am

'51 engine

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Re: Motor Sprocket (Tapered) Question

#4

Post by Hog54 » Fri Oct 26, 2012 2:42 am

You might have the key cocked.You should see the key on the front side before you put the nut on.

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Re: Motor Sprocket (Tapered) Question

#5

Post by john HD » Fri Oct 26, 2012 3:54 am

what are you using for a key?

john

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Re: Motor Sprocket (Tapered) Question

#6

Post by RUBONE » Fri Oct 26, 2012 4:33 am

There should not be any key visible on the backside when the sprocket is seated properly. if the sprocket is aftermarket the center hole may be suspect. And the key should look like the one on the top right in the attached picture. The threads normally begin about flush with the sprocket outer face and fill the entire nut when properly assembled. And that nut is on backwards!
Robbie
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Re: Motor Sprocket (Tapered) Question

#7

Post by 58flh » Fri Oct 26, 2012 11:46 am

Robbie Is DEAD-ON!--The key should not show & the chain running off-center tells you its wrong!--,Take it apart & check the key & keyway for burrs--file if needed!--Then put it back togeter & you should get real close without tightening the nut!,Once the nut is Tourqued on she will be good to go!---This happens alot when a sprokets been on that shaft a long time!--Check the keyways to!--Richie 8)

rozemab
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Re: Motor Sprocket (Tapered) Question

#8

Post by rozemab » Fri Oct 26, 2012 3:39 pm

58flh wrote:Robbie Is DEAD-ON!--The key should not show & the chain running off-center tells you its wrong!--,Take it apart & check the key & keyway for burrs--file if needed!--Then put it back togeter & you should get real close without tightening the nut!,Once the nut is Tourqued on she will be good to go!---This happens alot when a sprokets been on that shaft a long time!--Check the keyways to!--Richie 8)
Excellent Guys, I will pull it apart and inspect! When things were not looking right, I knew I needed to ask the expects.

Will post my findings, so some other dumb schmuck learns from it!

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Re: Motor Sprocket (Tapered) Question

#9

Post by George Greer » Fri Oct 26, 2012 4:01 pm

That would be me. :D

George

Robbie,

The two small keys in the middle of the photo is Oil Pump shaft keys (correct?).

What is the ID of the other ones?

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Re: Motor Sprocket (Tapered) Question

#10

Post by RUBONE » Fri Oct 26, 2012 4:29 pm

George,
The top key is for the pinion and oil pump drive gears from '54 up. The square one on the left is kicker gear for BT. As you mentioned, the middle ones are oil pump with the short one for feed gears and the long one for scavenge. The right side is for the sprocket on a taper shaft but also for the shafts themselves to the flywheel. The bottom one is for the sprocket shaft to flywheel on splined drive shafts. Not shown is the crankpin key which is very like the top one but thicker, and the clutch hub key which resembles the sprocket one but is physically larger.
Robbie

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Re: Motor Sprocket (Tapered) Question

#11

Post by Panacea » Fri Oct 26, 2012 4:40 pm

It's always a pain when you loose your keys :lol:

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Re: Motor Sprocket (Tapered) Question

#12

Post by RUBONE » Fri Oct 26, 2012 7:24 pm

But using the right one is the key to success! :wink:

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Re: Motor Sprocket (Tapered) Question

#13

Post by rozemab » Sat Oct 27, 2012 12:54 am

The sprocket was not fully seated on the taper. It looks like a piece of crud got wedged between the shaft and gear, near the key.

Key is in fine shape, slot on the gear survived too. (Key was on the bottom of the shaft thus I could not see the crud, I was thinking it was just the key, feeling with my finger. )

Cleaned up both surfaces with brake cleaner, and the sprocket fit deeper on the shaft.

What I learned:

- Make better notes on the fit and position of parts.
- Test fit parts before final assembly, I simply began to assemble the sprocket and clutch, chain, as a unit, my first step in the wrong direction.
- tranny all the way forward? Are you sure? It wasn't for me and it caused me to install sprocket partially on the shaft.


Rubone, why is the motor nut installed with the small shoulder against the sprocket?

Brian

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Re: Motor Sprocket (Tapered) Question

#14

Post by RUBONE » Sat Oct 27, 2012 1:20 am

Rubone, why is the motor nut installed with the small shoulder against the sprocket?
The one thing that holds the sprocket on is the taper. Not the nut, not the key they are merely top get it lined up and together. Once it is on they are redundent. The nut is designed to tighten with extreme pressure at the inner part of the sprocket and force the taper together. The taper also needs to be absolutely clean, no oil or residue of any kind on it. If seated correctly and tight, it could stay in place with no nut or key! Installing the nut the other way around defeats the designed in feature! And never try to put Loctite or anything else on a taper, it works by metal on metal only!
Robbie

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Re: Motor Sprocket (Tapered) Question

#15

Post by rozemab » Sun Oct 28, 2012 12:24 pm

Been thinking about this some more.

The key ID by Rubone is rounded. It is meant to rotate in the groove found on the shaft...?

If the key is seized in the groove, or simply has a 'set', it is possible the key not to rotate, aligning itself within the key way in the gear?

(I'm assuming the gear's key way is cut parallel to the taper, ie., it follows the taper.)

I inspected the key for damage but never took it out of the shaft. I doubt it has any free movement to rotate to allow it to align itself squarely in the key way.

If this is the case, what is the safest way to remove the key without damaging the shaft! Didn't occur to me to replace the key with a new one with replacing the gear.

Thanks, Brian

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