Topic: Bronze bushing Interference Clearance

[Guzziman]

Hi all,

Working on my 76 CB750F1

Bought some US made flared bronze bushings from Kibblewhite on EBay
OD on thes is 1.044” read after taking out of freezer
ID on my swingarm is reading around 1.033”

I don’t want to bugger anything. Is this too large a gap? Was going to do all thread to install

Thanks and any pointers appreciated.  I do intend to get my collar cleaned up and then get these honed for a .0008 collar to bushing clearance.

Thanks

[bryanj]

Never seen bushes that need honing and also never seen a collar that will clean and reuse sucessfully. Do youself a favour and do it right the first time with a new collar then grease the assembly frequently ( weekly or every 500 miles)

[Guzziman]

Thanks for the input.

The difference between 1.033 swingarm ID and the bushings outside diameter of 1.044 is .01” not .001”. Which is 10 times greater.  So I think I need to take this to a machine shop and not even attempt to install these. The vendor says in his ad that the inner diameter is purposely small so that they can be honed to preferred clearance by the owner.

Guzziman

[MauiK3]

0.010" is not a press fit, it won't fit.
One good way to really chill the bushing is to get some dry ice and isopropyl alcohol or denatured alcohol, put the dry ice in it and submerge the bushing. The alcohol will turn almost honey like and be really, really cold. Use tongs or pliers to handle the bushing, it will be so cold it would burn you.

[Guzziman]

I rechecked my swingarm in multiple places. It’s slightly oval shaped and clearance up to 1.040 which is much closer to bushing 1.043. I think I’ll try to run some wet dry on a close fitting deep socket/drill inside the swingarm.

Guzziman

[bryanj]

I am surprised a vendor sells things needing finishing with equipement the average motorcycle owner wont have

[754]

I am not. They sell prceision parts.
 Best way to get a prcise fit ix to hone to fit.
 Using bushings pre sized tbat do not need machining, has to in some case end up with mire ckearance tban desired.

 Keep in mind 2 things. Bushing will shrink with pressfit, and loe that uou are putting bushing in may stretch abd or change shape with a press fit.
 So really.. fitted AFTER Install ,  is the best it can be... if you have the right tools.

[bryanj]

That was my point IF you have the right tools

[Guzziman]

So I am going to clean up the swingarm. Do a kind of gentle home using drill with 17mm deep socket wearing 400 wet/dry

bushings in freezer

2 foot allthread is greased and ready

After I get these installed, what is the best tool to use?
A break master cylinder hone?  Use light motor oil?

Thanks

[MauiK3]

I would choose to not alter the swing arm since the bushing is a consumable. Perhaps chuck the bushings in a drill press and reduce the outside diameter.

[754]

 The point was , yes they sell high performance parts, not easy, one size fits all..
 A bit of out of round on the swingarm, a bit of wear on the sleeve, yeah everything FALLS  into place.
 And then 800 miles laterm you notice that it has play already..

 So choose easy with compromises.. or go through the pain of getting done the better way.
 Having to ream out a few thou means you can polish up and reuse your center  sleeve..

[Guzziman]

Valid point. Tonight I gently cleaned up the light marks from getting the original bushes out of the swingarm!  Checked the original collar. Very straight and only one thou difference.
14000 original miles and someone already installed the larger std grease nipple.

I previously changed out the steering bearings with all balls racing.
Looking forward to riding this thing when she’s all done.

[HondaMan]

Bronze bushings must be a press fit between 0.0004"-0.0008" (that is NOT a typo, it is less than 0.001" inch press fit).
If it is more than that, the bushing will either compress or collapse upon insertion. I have done hundreds of these arms by now...but I make the bushings to fit the arms, because very few of the arms are still round inside, but are oval. They will be longer toward the front on the left side and toward the back on the right side, due to riding stresses. Sometimes I have to straighten them by honing or even pressing before installing the new bushings - which I make to fit.

[flybackwards]

I used the Kibblewhite bronze swingarm bushings in my K7 rebuild. They were a tight press fit in the swingarm - few taps with the plastic mallet - I did have to remove the rust and assorted crap from the swingarm seats. I also replaced the collar and pivot bolt. I had the same finding that the bushing id was too small for the collar od - called Kibblewhite and he said that I needed to ream the id to fit the collar. You need a good quality adjustable reamer and a bit of patience and set up. I used a reamer from a delightful company called Chadwick and Trefethen in NH. Unfortunately I did not write down in my log the clearance I set up. The reamer is long and will self centre in one side of the swingarm while reaming the other - apparently reaming is more accurate and leaves a better surface finish than simply honing. Seems to work just fine.

[flybackwards]

Yes, I guess I should mention that the reamer is not cheap but it is a precision lifetime tool - around $150 as I recall - it got lost in the overall rebuild budget!

[754]

There is  lower price ones available like around  50 bux or maybe less.

[flybackwards]

Ah but its a lovely tool and they were so good to deal with...

[low-side]

If you can't afford the tool (or just don't want to spend the money on a tool you'll use once) that sizing operation wouldn't cost too much at your local machine shop.