Topic: Swing Arm Bushing replacement

[bryanj]

From experience of replacing these many times to get bikes through the UK mot test (US annual inspection) The pin is Always more worn than the bushes and in several cases a new pin on old bushes would have suficed--But didnt do that as customer was paying!-- 500, 550 and 750 are all the same parts with later bushes being "top hat" type so that you dont need the steel end caps and felt seals found on the early bikes. I have had one set that i just could not get out and had to have milled out, or would have if the customer didnt come up with a cheaper solution of a S/hand swing arm!

FINALLY Re-Grease EVERY OIL CHANGE or at least twice a year!!!!!!!!!!

[HondaMan]

 congrats and what kind of lathe did you get?
 
  I had a couple big monarchs, and a 12x32 hendy toolmaker lathe, but when I moved I got rid of them, the big monarch is what I made the wheels for my triumph on, (triumph hubs, comstar rims, custom 'spokes' made of 3/8 aluminum. all I kept were a 6x18 atlas and 6x12 craftsman AA type. went with a 9x20 as it was the biggest I can set up here.

once you get everything figured out and a few jigs set up you can fly through construction.

 I'm told online metals is a good source for bearing bronze. haven't used them, have some friends who work in toolrooms at local factories, and I get most material at cost from them.
 
  the shaft on mine was hard, but realy didn't feel like it was hardened

ken.
 

Mine is a "modelmaker" lathe, 7x10.
Those shafts are hardened, but Japanese style, which usually means case-hardening only. They cut slight grooves in the midsection (between the bearings) on the CB750 ones to make them stronger. These usually fit the other bikes, but they don't need the extra strength. I suspect that for most riders, the "lesser" 500 parts would suffice in a 750.

But then, I never was one of those... 

Update 8/2006: we've been through several swingarms now, and we're finding the K4 and later pivot shafts are NOT HARDENED. Apparently, Honda thought this was not needed (or too expensive to do) after the K3. None of the "F" units are hard. I have found hardened K1 and K2 units, but that's all. Since the bushings are softer, anyway, this makes sense.

[Terry in Australia]

But then, I never was one of those hetrosexuals... 

Fair enough mate, tell it like it is!

[mrbreeze]

Man,this has been one hell of a good post!!!! Gonna run it through the printer right now!!! Everyone in this post rules!!!!!!!!

[Orcinus]

Those shafts are hardened, but Japanese style, which usually means case-hardening only. They cut slight grooves in the midsection (between the bearings) on the CB750 ones to make them stronger.

I'm not sure that I understand how cutting grooves between the bearings makes a shaft stronger???

[Roach Carver]

I would much rather send the entire swing arm and pivot bolt and just have it done. Are there any diffs. in the k model swing arms?

[HondaMan]

Those shafts are hardened, but Japanese style, which usually means case-hardening only. They cut slight grooves in the midsection (between the bearings) on the CB750 ones to make them stronger.

I'm not sure that I understand how cutting grooves between the bearings makes a shaft stronger???

This increases the surface area of the shaft, relative to its diameter. Often done on racing parts and aircraft parts, to make them stronger. Strength of a shaft is highly dependent on the surface area: adding surface area to any given shaft, if done without sharp edges, increases it's rotational stiffness.

[HondaMan]

I would much rather send the entire swing arm and pivot bolt and just have it done. Are there any diffs. in the k model swing arms?

Well, "71", I just got the lathe set up: gonna take it to my machinist's house this weekend. He has a nice, big garage where we're gonna set up shop to make all sorts of CB750/500/550/... parts, like swingarm rebuild stuff, steering head washers for use with good Timken bearings, maybe even Timken complete sets. (I just installed a Japanese steering head set, for lack of having anything else, and I am REAL disappointed with its performance, so it's back to Timkens for me!)

Right now, I'm guessing about $80 to have someone send me their swingarm and shaft, and I'll send it back, rebuilt to .0008"-.0012" clearance. If we can find a good deal on the oilite brass, it will be a little less, because we'll build a bunch of "blanks" of the right O.D., then cut the I.D. to fit the pivot shaft and ellipse of the swingarm's tube after we get it.

I think all the K swingarms are the same (K0-K5).  Maybe one of the "F" guys could jump in here to tell me if they are also the same as the "K" series? I don't know from straight up about the K7-K8 swingarm, so you owners will have to chime in here, too.   

[HondaMan]

But then, I never was one of those hetrosexuals... 

Fair enough mate, tell it like it is!

Puttin' words in my mouth?
Gosh, don't tell my wife!

[Jerry Rxman Griffin aka MuthaF'er]

I think all the K swingarms are the same (K0-K5).  Maybe one of the "F" guys could jump in here to tell me if they are also the same as the "K" series? I don't know from straight up about the K7-K8 swingarm, so you owners will have to chime in here, too.   

The swingarm for the 75/76 750F has a different part number than the 77/78 F. The 75/76 F is a -392- designation which is 75/76 specific. Being a -392- eliminates most of the K's unless the 77/78 K uses a -392- like they do with the engines and some other parts.

[Orcinus]

The 77/78 F uses a -410- swingarm, so (as usual) it's probably unique... 

[Terry in Australia]

The swingarm bush diameters are the same for the later "F" and "K" models from memory Mark, but they wore "hats" so sit proud of the arm a couple of mm instead of flush. Sorry about the "ribbing" mate, but you were getting a little carried away with yourself, ha ha! Cheers, Terry.

[HondaMan]

The swingarm bush diameters are the same for the later "F" and "K" models from memory Mark, but they wore "hats" so sit proud of the arm a couple of mm instead of flush. Sorry about the "ribbing" mate, but you were getting a little carried away with yourself, ha ha! Cheers, Terry.

Yeah, me & my Honda - we be mates! Longer than my wife, by 8 years. 

Do you know if the "top hat" style will fit OK in the earlier "K" bikes? The main advantage of the "K"-style setup was the phenolic cap, fiber washer pair under the cupped washer, which helped keep the hi-PSI washers out of it. Trouble was, the felt washer usually dissolves itself and disappears...

[Terry in Australia]

I think they probably will fit Mark, but you really need to measure the gap betwixt arm and frame.

[HondaMan]

I think they probably will fit Mark, but you really need to measure the gap betwixt arm and frame.

While we're talking about this...I might recommend to others who want to work on swingarms: loosen the bottom engine mount bolt (holds footpegs on) when removing and reinstalling the swingarm. It helps keep the cuss words in. 

[pelicanwheel]

I had expected to complete my total and complete restoration on my '76 750 "K6", but got lazy most of the summer here in Phoenix.  constant 100 degree plus temps will do that to you.  So now I'm trying to get back to it so that I can have it done just in time for decent weather.  I have a couple questions for you guys:

1)  Regarding swingarms...I recall reading earlier this year about bushings...even bought something new off ebay (bronze) but have no idea what as I type this.  I'll have to look at it when I get home.  What I do remember is that when I look at my swing arm, it looks like the bushings are permanantly installed...or that they are of the hat type and it seem like they may have been welded!!!???  I'm sure I'm remembering wrong, because I'm the second owner of this bike, and the first owner died after buying the bike 3 months earlier.  The big problem, though, is that I had the swing arm powder coated with the bushings in!!  Yikes.  Any ideas on how to get them out without screwing up the paint?

2)  Off topic, but is there a consensus on EXACTLY what parts to use for the steering bearing conversion? Or is this still in debate/

3)  And lastly, it seems that when you guys list bike models..you always list k0 - k5, then skip to the F models...did the K6's convert to communism and move to China...therefore we don't talk about them?  I know I jave a K6 and often that model is omitted.  Why?

Thanks!

Pelican

[pelicanwheel]

Ok..I'm home now and took pics of my swing arm.  its hard to tell with the real thing in front of me (let alone from the pics here) how the bushing is attached.  Perhaps it's pressed.  But what is really interesting is that the inside tube appears to run all the way across.  Is this the tube you guys referrence in this thread?  Am I suppose to tap it out with a drift first?  Does the tube suppose to pivot on the rod that goes all the way through?

Any help would be appreciated.

Pelican

[Terry in Australia]

Yeah mate, K6's are the last of the "real" K's, and I reckon they're great! Now with your swingarm, what you've got is the steel sleeve that pivots inside the bushes, you need to drive it out with a soft brass drift is it's real tight, then you need to remove the bushes by inserting your hacksaw bladethru the swingarm and cut thru (reattach your hacksaw frame) your old bushes and push them out and insert the new ones, and make sure you feed plenty of grease in there! Cheers, Terry.

[bryanj]

I'm 98% certain the top hat bushes will fit as long as you leave out the phenolis thrust, felt seal and galvanised cup washer, Not OK for Nit-Pickers and super purists but well OK for general use

[brian]

Just a quick question , how do you determine when the rear bushings need replacing ? How do you test , what is the allowable movement of the rear tire side to side if any ? It's always something

[Terry in Australia]

Any side to side movement indicates that you need new ones mate, otherwise don't go fast around corners................

[brian]

Thanks Terry , I do seem to have a little movement at the back tire . Time to check out bushings

[HondaMan]

Honda's "Service limit" was .0023" slop. This translates to .0414" looseness at the rear axle (about 1/32").

Replacing the stock "K" style bushings with "F" style presents no real problems, so long as you grease often. The "K" style had cups with fitted phenolic "top hat" retainers for a felt washer in each side. This contained the grease and held out water. The "F" style has a cup with a seal inside that rides on the edge of the "top hat" style of bushing. This seal will be missing if you substitute "top hat" bushings into a "K" setup.

Most of the time, the shaft that goes through the bushings has worn itself oval and is smaller than stock. I offer a service where we take the shaft and turn it round again, then make custom-fit bushings that are set for .0008" (Honda minimum) clearance AFTER installation, guaranteeing that it comes out round in the end. If the swingarm itself is oval (common), then we undersize the ID bushing holes and hone to fit round after installation. This installation will live longer than the bike. See my "Lathe Services" post under "Services" in the HOME area of this forum.

[HondaMan]

I would much rather send the entire swing arm and pivot bolt and just have it done. Are there any diffs. in the k model swing arms?

Sorry, been gone fixing Fords for a while... 

The "K" swingarms were all the same from K0-K6. The "F" is different, and I think the last K7-K8 ones were different again, but more like the "F" units.

[HondaMan]

The swingarm bush diameters are the same for the later "F" and "K" models from memory Mark, but they wore "hats" so sit proud of the arm a couple of mm instead of flush. Sorry about the "ribbing" mate, but you were getting a little carried away with yourself, ha ha! Cheers, Terry.

Terry;

In case you're interested, I have a dimension now on that "shoulder": it is 1.25" OD and it is .077" to .079" on the ones we have seen from Honda. If you go to .084" on the shoulder, the shaft is too short and the assembly won't stack up right on reassembly, making a very stiff pivot. So, we're making them match the ones we remove from the swingarm being rebuilt at the time, just to guarantee fits.