Balancer Shaft

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knackeredMk1
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Balancer Shaft

Post by knackeredMk1 » 22 Feb 2010, 14:11

Balancer shafts and bearings do wear out. Particularly the needle roller bearing under the generator cover. If there is a squealing/whining noise or constant grumbling then this might be the balancer shaft.

You can test if the balancer shaft is making the noise by removing the balancer shaft drive gear and then running the engine.

Easy to get the shaft out - (Words by Reevo)

Remove the clutch case and the clutch, take the nut off the balance shaft and it will just push out through the generator side.
It is unlikely that the bearing on the clutch side will need changing ( mine was fine even though the needle bearing was goosed and making a right racket). If your going to change it any way you need to undo the 2 lock tabs that hold it in place, unfortunatly one of them is behind the gear selector gizmo. To get this out, remove the gear lever, undo the 10mm bolts on the gizmo and pull towards you (be careful not to loose any of the bits that sit in the end of the selector drum). The gear selector shaft does not need to come all the way out, just enough to get to the locking tab that holds the bearing in place.
The needle bearing outer case will most probably cause you some trouble, mine did. I read on here that you can use a dremel with cutting disk to assist with removal but I couldn't get mine in. I had to ream out behind the bearing case so i could get a bar in behind it and smash it to bits.


Alternatively you can make a balancer shaft needle bearing remover tool.
Image

Parts needed:

The clutch side bearing is pn. 91002KAE003 size - 17x37x12

The needle roller bearing is pn. 91005KAE741 size - 25x34x14

The seal you will need is pn. 91201KAE003 size - 25x37x6

All balancer shafts are basically the same across Mks,

Be careful when you do the work & watch which way the 'blue' washer is round and make certain everything goes back as it came out.

You may need to replace the balancer shaft or have a new surface applied by an engineering firm. Some have done this and used a brass collar to replace the worn surface.

There is quite a lot of evidence that when you replace the balancer shaft or needle roller bearing you need to replace both at the same time. It seems that if you replace one without the other you get very accelerated wear of the new part.

When reinstalling the balancer shaft this is the setup - (The photo is from a Mk1 which needs another punch mark on the crank drive gear (in line with the Woodruff key) to line up the (underneath) cush drive system that is not present on the other models).

Image

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New Balancer Shaft

Post by knackeredMk1 » 28 Feb 2010, 14:10

New balancer shaft (02/10) ~ £88.

(12/12) ~ £100.

(01/14) - £118.15.

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Re: Balancer Shaft

Post by knackeredMk1 » 30 Dec 2010, 10:28

The balance shaft can be isolated without removing it by replacing the drive gear on the main shaft with a spacer. This, as with removing the balnce shaft, apparently improves throttle response but makes the bike a bit vibey when used on road. I suspect it also removes some of the 'tractor like' ability the bike has in really muddy conditions.

In Japan racers tend to remove the balance shaft and associated bearings completely but you have to put a cap over the space left in the LHS crank case.

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Re: Balancer Shaft

Post by knackeredMk1 » 04 Jun 2012, 01:44

Balancer shafts can be ground and sleeved by:
Service Exchange Parts
39 sideley rd
kegworth
derbyshire
DE74 2FJ
01509 673295
info@sep-kegworth.co.uk

Cost ~ £45


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