Swinging Arm Bush appears to be a non standard size, why?

[leadnavel]

I’m a good way through my 750 K7 rebuild and thought that I would replace the bushes for the swinging arm as the end of one of the existing units are a bit knarled (image attached), here’s the problem, the replacement bushes from CMS (part number:52108-457-300) measure up different from my existing bushes! The inside diameter of the new bushes measure 21.80mm, the inside diameter of the old bushes measure between 21.39-21.40mm. In short the new bushes have a larger inside diameter than the old ones, so it’s defo not a ware issue!

I have questioned the part with CMS and they assure me that the correct part has been sent for the K7. I have also measured my existing Center Collar which measures between 21.34-21.38mm at the bush ends. I’ve had the bike since 1983 with very few modifications to it and she’s been off the road since 1986 (27’000 miles on the clock) so very few parts are worn. Does anyone know what’s going on here? Luckily I haven't taken out the old bushes as I would've been right up dump dyke!

[Nurse Julie]

Are the ones you received from CMS the original plastic type or the bronze bush replacement type?

[Nurse Julie]

Just measured the ID of the bronze Bushes I sell for the 750/4's and its 21.40mm.

[leadnavel]

Are the ones you received from CMS the original plastic type or the bronze bush replacement type?

Thank you for your reply Nurse Julie, the parts that I got from CMS are of the plastic type. Can you shed any light as to why my bushes differ from the parts that CMS say are the correct replacements for my K7?

[Nurse Julie]

Are the ones you received from CMS the original plastic type or the bronze bush replacement type?

Thank you for your reply Nurse Julie, the parts that I got from CMS are of the plastic type. Can you shed any light as to why my bushes differ from the parts that CMS say are the correct replacements for my K7?

Absolutely no idea. What I do know is that the bronze bushes I sell fit the complete CB SOHC/4 range of bikes, including all the 750's K0-K8 and F1/ F2.
Looking at what I can see in your photo, is yours a standard swing arm?

[Nurse Julie]

One other thing, I've just measure the ID of a set of the OEM plastic bushes and they also measure 21.40 ID.

[Tomb]

The OEM type being plastic, and presumably a tight fit in the swing arm, would they not have a much bigger outside diameter, and crush somewhat when fitted? this may bring the ID down in size when fitted. Julies bronze bushes will not do this much therefore need to be "size" before being fitted.

Just a thought.

[Trigger]

Nope, still 21.40 when oem plastic bushes are fitted 

[leadnavel]

Are the ones you received from CMS the original plastic type or the bronze bush replacement type?

Thank you for your reply Nurse Julie, the parts that I got from CMS are of the plastic type. Can you shed any light as to why my bushes differ from the parts that CMS say are the correct replacements for my K7?

Absolutely no idea. What I do know is that the bronze bushes I sell fit the complete CB SOHC/4 range of bikes, including all the 750's K0-K8 and F1/ F2.
Looking at what I can see in your photo, is yours a standard swing arm?

As far as i'm aware my swinging arm is of the standard variety, what do think, is it? (image attached)

[Nurse Julie]

Yes, it looks to be, it was all the chrome that threw me of track.
So really, even though CMS insist the bushes they have sent you are correct, they are obviously not. I'm wondering if they are using a superseded part and although the OD may be correct, the ID is incorrect.

[leadnavel]

The OEM type being plastic, and presumably a tight fit in the swing arm, would they not have a much bigger outside diameter, and crush somewhat when fitted? this may bring the ID down in size when fitted. Julies bronze bushes will not do this much therefore need to be "size" before being fitted.

Just a thought.

The plastic material that the bushes are made from seems too stiff/brittle to be crushed down at all Tomb.

[leadnavel]

Thanks for your help guys. I have asked CMS for a refund on the parts but I have had no response, it seems to have fallen on deaf ears!

[Nurse Julie]

Thanks for your help guys. I have asked CMS for a refund on the parts but I have had no response, it seems to have fallen on deaf ears!

Oh dear 😕😕😕 I would be good to have an explanation from CMS how they sell them for that model but they don't fit 🤔🤔🤔

[leadnavel]

Just an update for you chaps... I contacted Dave Silver Spares who were very helpful and removed a bush from a sealed Honda factory package (52108457300 bush) and checked the I/D, they also say that the I/D is 21.80mm?! After reading some other posts on here, and the other place, I remeasured my Coller using a micrometer rather than a vernier gauge, the measurements come back pretty sound (no ovality) on both bush ends. Between 21.40-21.43mm. There's definitely something strange going on here!

[Bryanj]

Being as its plastic it may close up enough but you would have to fit it to check, have you measured the od of the bush and id of the arm?