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-   -   Seized rear F4 Hub- advice please (https://www.mvagusta.net/forum/20-maintenance-tech-issues-all-4-cyl-models/241345-seized-rear-f4-hub-advice-please.html)

mitchy 03-14-2019 10:06 PM

Quote:

Originally Posted by Chilblane (Post 2563777)
Yes I will do that anyway (document pictures) but in the worst case scenario a swing arm bored off 90 degrees, thats an expensive lump. I rather doubt that is the case as the hub definitely does not look straight or measure so relative to the swinging arm, so hopefully just a new hub and drive!

Can you beg,steal or borrow a 1 metre long straight edge,then check the alignment yourself by sitting it against the rear sprocket,then along to the front sprocket.
I would doubt very much if the swing arm has been machined out of alignment.
Have you checked for any movement in the hub with the rear wheel on yet?
That is the first thing I would do.
Next check your sprocket carrier/cush drive rubbers and spacer for any wear.

theknurl 03-15-2019 04:00 AM

?
 
My vote?
The POS 2nd Gen cush drive is wrong or there is an extra washer on top of the hat shaped spacer......
a that would give you the wear on the inside of the countershaft sprocket :wink2:

Chilblane 03-15-2019 05:45 AM

Quote:

Originally Posted by mitchy (Post 2563955)
Can you beg,steal or borrow a 1 metre long straight edge,then check the alignment yourself by sitting it against the rear sprocket,then along to the front sprocket.
I would doubt very much if the swing arm has been machined out of alignment.
Have you checked for any movement in the hub with the rear wheel on yet?
That is the first thing I would do.
Next check your sprocket carrier/cush drive rubbers and spacer for any wear.

As most members have said the hub is abnormally stiff and needs investigation so I will try and remove it over the weekend and verify the condition of the swing arm bore and hub surface.

There is no movement in the hub with the wheel in situ. I can carry out an alignment check as well, and inspect the Cush drive when I get the bike's rear end off the ground.

Chilblane 03-17-2019 08:24 AM

4 Attachment(s)
The hub was successfully extracted after the Cush drive removed. Now with better access the gap measured between the hub and face of the swing arm was at its worst 3mm varying axially as previously mentioned. Attached is an out of focus picture but you can just about see the gap. The hub surface condition is excellent. Swing arm bore surface generally the same save for some minor marks confined to approx 35mm long x 10mm wide at about 7 o'clock position (not easy to photo) Hub returned to swing arm after a couple of burrs were filed off the teeth, presumably caused by the force of the C wrench. Hub now hard up against the swing arm OK. Trial torque the hub bolts at 25Nm has now returned the slot in the swing arm to a parallel slot/gap. Finally pinch bolts then slackened and C wrench allows easy hub movement.

After cleaning up surfaces of the shaft and and hub there are signs of scorching on the sprocket side bearing. The sleeve of that bearing removed and its I/d varies by 0.08mm. Is that within tolerance?

The rear sprocket was cleaned up and the wear on the inner side is clearly variable, and is not flat when laid on a glass surface!

Chain alignment chain checks were not taken, as I think most would agree that the hub not sitting square in the swing arm bore is the cause of the problem.

If the tension bolts have been over torqued is it possible this could have damaged the hub body? I do not have a vernier large enough to check for any ovality.

If advice would be to replace bearings and seals in the existing hub, where are quality components available?

Of course the other question is how did the hub manage to be out of alignment in the bore of the swing arm (although now superfluous) interesting and maybe the distorted rear sprocket provides a clue?

Many thanks to everyone that helped me out of this jam (no pun intended):smile2:

silentservice703 03-17-2019 08:55 AM

Contact @theknurl for bearings and seals

Chilblane 03-17-2019 09:26 AM

Quote:

Originally Posted by silentservice703 (Post 2564337)
Contact @theknurl for bearings and seals

silentservice703

Thank you I will. Forgot to ask in my previous post is 0.08mm out of spec for a bearing of this type?

Chilblane 03-18-2019 04:28 AM

Quote:

Originally Posted by theknurl (Post 2563971)
My vote?
The POS 2nd Gen cush drive is wrong or there is an extra washer on top of the hat shaped spacer......
a that would give you the wear on the inside of the countershaft sprocket :wink2:

PM sent Sunday:smile2:

theknurl 03-18-2019 06:36 PM

?
 
2 Attachment(s)
Chilblane;
Got your message......
Please post pictures of the inner races of the needle bearings
So far only one person has had a needle bearing failure......the inner seal was cut and all the grease went into the
center of the hub
Deburr the spacer that goes between the inner races of the needle bearings
It appears that there has been some water intrusion......was the sprocket nut tight?
If the 6810-2RS bearing is smooth when turned with your fingers use it again
DO NOT TORQUE THE PINCH BOLTS TO MORE THAN 15LBFT/20Nm

Here's what Factory torque numbers can do to a 1st Gen hub.....this is a double row bearing, only one row failed
the one inside the hub....the other one is inside the caliper bracket >:)

Chilblane 03-19-2019 07:02 AM

4 Attachment(s)
Quote:

Originally Posted by theknurl (Post 2564521)
Chilblane;
Got your message......
Please post pictures of the inner races of the needle bearings
So far only one person has had a needle bearing failure......the inner seal was cut and all the grease went into the
center of the hub
Deburr the spacer that goes between the inner races of the needle bearings
It appears that there has been some water intrusion......was the sprocket nut tight?
If the 6810-2RS bearing is smooth when turned with your fingers use it again
DO NOT TORQUE THE PINCH BOLTS TO MORE THAN 15LBFT/20Nm

Here's what Factory torque numbers can do to a 1st Gen hub.....this is a double row bearing, only one row failed
the one inside the hub....the other one is inside the caliper bracket >:)

theknurl,

Thank you, you have reminded me of what I forgot to mention at the weekend. The sprocket side nut was certainly not as tight as when I have slackened the wheel side (as a comparison) set at 200Nm by me, I have never slackened the sprocket side before.

Pictures attached of the inner races, confirm little or no burrs on the spacer. The 6810-RS is very smooth, and there is no grease leakage in the centre of the hub.

With the camera out have I taken a picture of the calliper support flange...is the position of the ABS/TC sensor correct? the manual shows it in a horizontal position but photo there does not have the same type of flange with a position option.

Many thanks for all your advice:smile2:

Chilblane 03-27-2019 07:37 PM

1 Attachment(s)
All back together now, I hope troublesome hubs will be a thing of the past!


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