Magnum 2 swingarm bearing code

[Dezza]

Does anyone know the code for the bearings in a stock Magnum 2 swingarm, the ones that combine 2 different needle rollers together? The last lot I bought were from Harris about 20 years ago but I didn't write the code down

[Toecutter]

Oooh, i did some recently. I'll have a look back at paperwork for the bearing part number. I'm popping into work Saturday afternoon so will let you know. 

[Dezza]

2 hours ago, Toecutter said:

Oooh, i did some recently. I'll have a look back at paperwork for the bearing part number. I'm popping into work Saturday afternoon so will let you know. 

Smashing. Many thanks

[clivegto]

If @Toecutterfails to find the part number I have a standard arm laying around with the bearings in I could pop out the arm for a look see. 

[Dezza]

2 hours ago, clivegto said:

If @Toecutterfails to find the part number I have a standard arm laying around with the bearings in I could pop out the arm for a look see. 

Thanks, that may be useful. I now have a standard arm that needs refurbishing but the bearing codes aren't on the outer faces . Yours may be different though.

[clivegto]

I have measuring stick

[Dezza]

They are a strange sort of bearing, a needle roller combination of a thrust bearing and normal cage rolller in the same unit. I think they can only be measured accurately after removal. I need to fit a new front and back end before having the frame and swingarm recoated so I can't remove the old bearings first as if I did I'd have a 10mm gap between the swingarm pivot and the frame.

This type of bearing seems to be available from specialist suppliers but they aren't cheap. i think they were aboiut 45 quid each 20 years ago and they pose a considerable challenge in fitting: you can't wack them in as such as otherwise this will destroy the thrust part of the bearing.

Edited December 13, 2025 by Dezza

[imago]

If anyone's got a picture and/or measurements I can have a word with the bloke at Central who sorts out all the oddball bearing stuff for me. He has access to a ridiculous number of manufacturers and they can sort pretty much anything.

It was him who got those GSX crank ball bearings sorted with an annular groove. They weren't available off the shelf anywhere as the stock stuff had a 1.5mm groove and the Suzuki locating rings are 2mm.

[clivegto]

It is indeed a thrust and roller bearing so 2 bearings in 1. My F1 swinging arm bearings look to be the same as the Magnum 2 as well. 

        

[Dezza]

That's very helpful. Thanks. What is the o/d of the bit that goes into the swingarm?

Also, what is left of Harris have come up with zilch, even though they offer to help 'repair' genuine Harris frame kits (who will do this I wonder?). They now can't even supply the bearing code for their most popular frame

[imago]

If you can get the OD I'll ask him to price them up on Monday. They're pretty widely available here for example so it's just a question of price really.

[Toecutter]

Unfortunately I didn't have time to pop in today. Apologies. I can grab the part no. Monday if still required?

Cheers,

T.

[clivegto]

Hear you go 

 

[imago]

So just to confirm, is it a 20mm ID/spindle? Giving 30mm overall length with a 10mm thrust, needle roller OD 37mm and ID 20mm.

I'll ask him for a price and a past number.

[imago]

2 hours ago, Toecutter said:

Unfortunately I didn't have time to pop in today. Apologies. I can grab the part no. Monday if still required?

Cheers,

T.

I'd say yes it's worth having, and then those that need them can order from wherever they want. 

[Dezza]

3 hours ago, Toecutter said:

Unfortunately I didn't have time to pop in today. Apologies. I can grab the part no. Monday if still required?

Cheers,

T.

Number would be most useful

[Dezza]

Update: Mark from 'Harris' (Royal Oilfield) was helpful in the end and got back to me with some numbers. He must have spent some time and effort searching through old records so well done him .

Apparently the bearing code is: NKX25Z, with an inner race also needed: IR20-25-30. A basic interweb search brings up bearings that look correct.

Toecutter, does this concur with the parts you recently obtained?

[Toecutter]

10 hours ago, Dezza said:

Update: Mark from 'Harris' (Royal Oilfield) was helpful in the end and got back to me with some numbers. He must have spent some time and effort searching through old records so well done him .

Apparently the bearing code is: NKX25Z, with an inner race also needed: IR20-25-30. A basic interweb search brings up bearings that look correct.

Toecutter, does this concur with the parts you recently obtained?

The part no I have is NAX2530Z bearing assembly 25x43x30mm which are £37.91 each plus VAT from simply bearings. Maybe cheaper from elsewhere. As mentioned an inner race is also required. The part number above looks correct too.

[Dezza]

3 hours ago, Toecutter said:

The part no I have is NAX2530Z bearing assembly 25x43x30mm which are £37.91 each plus VAT from simply bearings. Maybe cheaper from elsewhere. As mentioned an inner race is also required. The part number above looks correct too.

Thanks, that's a big help. How did you fit the new bearings? I am guessing they have to be very carefully pressed in after cooling the bearings first in a freezer. I think that's how I did my last lot but I can't remember exactly. Obviously, the swingarm can't be heated as that will bugger up the paint.

[gray711]

Can’t you heat it with a freshly boiled kettle- done that before on wheel bearings that have been in the freezer department, slipped in a treat  

[Dezza]

1 hour ago, gray711 said:

Can’t you heat it with a freshly boiled kettle- done that before on wheel bearings that have been in the freezer department, slipped in a treat  

Dunno. It's possible I suppose. I am puzzled as to how they go in fully without the use of force, which will obviously potentially risk buggering up the thrust part of the bearing.

https://simplybearings.co.uk/shop/p556652/NKX25Z-Budget-Needle-/-Ball-Thrust-Bearing-with-Closure-Ring/Cover-25x37x30mm/product_info.html

 

Edited December 15, 2025 by Dezza

[Toecutter]

They are a bit of a bugger to get in. I used a sash clamp to press them in with a piece of material turned down to seat on the outer edge to protect the bearing.

They are v tight and a bit fiddly. You could start them off square, carefully then press them in on a normal press. Just have to ensure everything nice and clear of powdercoat to allow them to pop in square.

Good luck.

[Dezza]

They're v expensive too as well as being tight and fiddly. On my Spondon it uses on each side two seperate bearings: a needle roller thrust bearing and a cage needle roller pressed into the swingarm. This seems a better thought out design than that used by Harris.

[imago]

As @Toecuttersays, they can be pressed/pulled in without issue, it's smacking them in that causes the damage.

You can use clamps, a press, a length of threaded bar through the centres, a puller from the other side etc. Basically anything which applies an even pressure as that's what they're designed to take even when they're not rotating. 

[bluedog59]

I use the boiling water/freezer method on bearings and it always works a treat. Bearing in a sealed bag with maybe a squirt of WD40, couple of hours in the freezer and boiling water over whatever it's going into.