A7750 rotor replacement

[doncroce]

Hi RWI

I am trying to replace the rotor of my A7750. I bought the following parts from cousinsuk:

VAL77501491 - Valjoux 7750 1491 Oscillating Weight Bolt
P38796 - 7750 Key for Oscillating Weight Bolt
P19255 - Horotec Multi Functional Tool Hand Piece

Oscillating Weight Nickel Plated (Without Ball Bearing 1497) ( 1143 ), Valjoux 7750 (VAL77501143)

Screw For Oscillating Weight ( 51143 ), Valjoux 7750 (VAL775051143)

Ball Bearing ( 1497 ), Valjoux 7750 (VAL77501497)

See picture for the parts and tool (screw is not pictured): http://i.imgur.com/9Lzl6Vn.jpg

cost me around £120...

Now the issue is that I can't attach the ball bearing to the oscillating weight. I am following a tutorial on youtube: https://www.youtube.com/watch?v=z8-f0hyIqxE

He even has the same tool (!) and it goes so smoothly.

However, I can't attach the ball bearing using the bolt ... it simply wont hold - I am turning the tool clockwise around 45 percent, but when I remove the tool all parts fall apart again.

When I used a lot of force pressing down the tool, I even scratched the rotor surface a little

How is this supposed to work? I thought replacing the rotor would be a trivial task, however after dozens of tries I gave up. What am I doing wrong?

Thanks for any help, I'm really desperate.

 

[KBH]

Does your rotor oscillating weight have the four tabs that the bolt slides under? If you're accidentally trying to put it onto the original Asian oscillating weight, it won't work.

 

[KBH]

Or, are the tabs on the bearing? I can't tell from the pictures but that would obviously be the key to getting it together.

The Asian rotor bearings seem to be just pressed in.

 

[doncroce]

Or, are the tabs on the bearing? I can't tell from the pictures but that would obviously be the key to getting it together.

The Asian rotor bearings seem to be just pressed in.

Thanks for your reply.

I am of course trying to attach the bearing to the gen rotor weight - the bearing has the correct tabs that fit the bolt, but I can't twist the bolt to "lock" the bearing to the rotor weight, it simply doesn't work

 

[KBH]

I wish I could help. As you say, it sure looks easy in the video.

 

[idinwo01]

So the bearing, rotor, and bolt are all gen?

If so, you should check that the bolt can lock onto the bearing without the rotor. If this can't happen, you already have a problem independent of the rotor.

 

[doncroce]

So the bearing, rotor, and bolt are all gen?

If so, you should check that the bolt can lock onto the bearing without the rotor. If this can't happen, you already have a problem independent of the rotor.

Yes all parts are gen. And yes, the bolt can lock onto the bearing without the rotor - I honestly do not know what I'm doing wrong...

 

[idinwo01]

Alright, well I need more to work with to help you trouble shoot. Can you take some pictures of the parts (if you don't have a nice camera, just hold a loupe to your camera for macro shots) or even a video of you attempting the install.

 

[doncroce]

Alright, well I need more to work with to help you trouble shoot. Can you take some pictures of the parts (if you don't have a nice camera, just hold a loupe to your camera for macro shots) or even a video of you attempting the install.

Hope this helps, let me know if you need more close up photos...

https://imgur.com/a/BVsh5

Honestly it looks more scratched than it is, this is my desperation that shows

As for the process, I'm assembling everything like in the pictures, then using the tool to rotate the bolt.

One thing I noticed that my tool looks slightly different than the one in the video tutorial I posted, but the bolt alone fits very nicely on top of the tool (there are appropriate slits for the tool to hold on to). The round protruding part has a spring so when I press down the tool on the bolt, it holds the bearing in place.

After rotating the bolt with the tool, the bearing seems still to spin, it never attaches it to the bolt and after removing the tool all falls apart.

Thanks a lot for your help dude!

 

[idinwo01]

[MENTION=105037]doncroce[/MENTION], wonderful job with the pictures my man.

You said "the bearing seems to still spin" when rotating the bolt, and this is what I guessed. It seems the bolt is rotating the bearing instead of sliding into the groves.

In the video, the guy is placing the rotor on a staking block to elevate the bearing. While a staking block isn't necessary, the elevation is. Are you elevating this so that the bearing is touching something solid while the rotor hangs freely?

 

[doncroce]

I've got good news and bad news.

I managed to correctly assemble everything - you recommended to use a staking block or some sort of elevation. I've used wood and metal pieces, but it didn't work. Then I added some adhesive double sided tape (really strong one) to a credit card (perfect elevation), added the bearing and rotor. Now the bearing couldn't move at all anymore, and I was able to attach the bolt - with a lot of force, to say the least.

The bad news is that the gen rotor does not properly replace the rep rotor, at least with my movement - the gen rotor has an additional thin ring on the bottom, while the rep doesn't have this ring. The result is the gen rotor / the ring under the gen rotor scratching some small parts in the movement while rotating..

Well I think it's been fun to play with this, even though it was a bit expensive.

Maybe I'll sell the rotor including bearing on the m2m forums.

Regardless, thanks to [MENTION=37538]idinwo01[/MENTION] and [MENTION=9883]KBH[/MENTION] for holding my hand...

 

[idinwo01]

No problem [MENTION=105037]doncroce[/MENTION], glad I could help. Sorry I didn't have any first hand experience with the 7750 movements. So the take away here is that a gen rotor swap isnt possible in asian 7750s? Did you see this consensus elsewhere in the forum?

 

[doncroce]

[MENTION=37538]idinwo01[/MENTION] at least not with my movement version (I posted a link). But honestly I didn't specifically search if the rotor is swappable with gen, but I definitely read somewhere that in general it's possible to swap a good chunk of the parts with gen and it will fit properly.

 

[idinwo01]

[MENTION=37538]idinwo01[/MENTION] at least not with my movement version (I posted a link). But honestly I didn't specifically search if the rotor is swappable with gen, but I definitely read somewhere that in general it's possible to swap a good chunk of the parts with gen and it will fit properly.

Seems like there is mixed success, but this will be a nice thread for the next person to encounter your issue.

 

[pippo]

I know the thread is very old, however...is it possible to complete the task without the proper tool?