Swing Arm Play

I have a MkIII Commando that only has 5,000 recorded miles.....corrosion has pretty much destroyed the finish, but everything comes undone despite appearances, all fasteners appear to be untouched and everything seems to be barely worn....I last had a Commando 20 years back, and apart from a couple of rotaries it's all been old Japs, so I'm a little out of touch.

The rear swinging arm had a small amount of free play at the rear wheel, which came as a surprise.....probably less than 1/8" but more than I want to see, the play is not in the isolastic cradle and the cotter pins were tight.

I removed the spindle, it came out very easily....possibly too easily, and it is bright, rust free and there is very little wear marking on the hard chrome finish, it looks almost as good as new.

I concluded the wear (even though I was convinced there shouldn't really be any given the lack of use) must be in the bushes, so I removed them and sure enough when offered to the spindle they are a sliding fit with a tiny bit of slop......despite the fact there was hardly a mark on them either.

I ordered new bushes from Andover, offered them up to the spindle....and they are exactly the same as the ones I just removed! a sliding fit with a tiny amount of slop.

I dont want to invest in a new spindle only to find it's no better, and this bike is already a horrific money pit anyway....has anyone had the same experience? am I trying to get rid of play that is regarded as perfectly normal?

Mick..................kettle738

I saw the same thing, build tolerances of the day. The swing arm weldment has variation in the alignment of the two sleeves, so, (relatively) loose bushes assured it would all bolt together. Custom machining of new bushes if you want better. :mrgreen:

CNW has a mod for this. Bushes are replaced with needle bearings.

kettle738 said:

I ordered new bushes from Andover, offered them up to the spindle....and they are exactly the same as the ones I just removed! a sliding fit with a tiny amount of slop.

Click to expand...

But did you try it with the new bushes fitted to the swinging arm?

As concours said, the S/A bush sleeves are often slightly out of alignment :roll: which may effectively remove the play.

I found the same thing during the rebuild of a 71 Commando this year. Play at the rear wheel traced back to the swing arm assembly. I replaced the bushings (no wear visible on the spindle) yet the safety mechanic claimed there was still too much play. These machines will never be as tight as new Japanese bikes so the solution becomes easy: replace the mechanic.

BC
Toronto
TR6P
71 Commando

Assuming the spindle/bushings are in good shape, that rear wheel play will be eliminated with swing arm collars. Mine was the same way with new bushings/spindle; adding SA collars eliminated all play at the rear wheel Here's an example of the collars: http://www.inoanorton.com/docs/swingarm.pdf

IMO, they are one of the "must do" mods for a Commando.

mike996 said:

Assuming the spindle/bushings are in good shape, that rear wheel play will be eliminated with swing arm collars. Mine was the same way with new bushings/spindle; adding SA collars eliminated all play at the rear wheel .

Click to expand...

Mike, in Mick's case, the collars will not remove the play associated with loose bushings.

As LAB said, try them after pressing them in the swing arm. It maybe be part of the manufacturing process and in the design to keep the machined dimension a little loose for fitting purposes.

These bushings are soft, very soft and will constrict.

Be cautious when installing for the dish will surely crack if you are rough with it.

Soak in oil over night.

I have had the split ring mod for years but after servicing my spindle last week, just a check, I question its necessity. When things are fitting proper, there is no play to take up. Anyway, the holes are drilled and I keep them plugged up with the mod. :lol:

Remember, the spindle does not move and is held in place by the weak 1/4-28 center bolt (Get a new spec 8 bolt when assembling - 30 cents buys a good amount of security in this regard.) and unless previously damaged, there is nothing to wearout here in the middle.

I do not know if mod works but I believe it can't hurt but I'm not sure why. It is a last resort to mend a needed repair and/or to avoid making a parts purchase.

What the mod will do is keep the spindle from spinning if the weak s.o.b. center bolt is broken and you cannot get it apart. Not uncommon.

Upon assembly I find these tip useful. Tighten the long central screw through the spindle while have the new spec 8 center bolt located in the spindle but not tightened yet. Then tighten the new spec 8 center bolt, THEN the apply the split collor mod. This procedure keep the spindle central for best oil flow. Nothing but 140w will do.

pvisseriii said:

Remember, the spindle does not move and is held in place by the weak 1/4-28 center bolt (Get a new spec 8 bolt when assembling - 30 cents buys a good amount of security in this regard.) and unless previously damaged, there is nothing to wearout here in the middle.

I do not know if mod works but I believe it can't hurt but I'm not sure why. It is a last resort to mend a needed repair and/or to make a parts purchase.

Click to expand...

However, Mick(kettle738)'s Commando is an 850 MkIII which already has a positively-located double cotter pinned spindle (no central 1/4" bolt) therefore the Kegler conversion is unnecessary (I'm not exactly sure there would even be enough space to fit the Kegler clamps to the MkIII cradle tube?). Any apparent play in the MkIII S/A assembly should (at least, theoretically) occur between bushes and spindle.

http://www.oldbritts.com/1975_g16.html

L.A.B. said:

pvisseriii said:

Remember, the spindle does not move and is held in place by the weak 1/4-28 center bolt (Get a new spec 8 bolt when assembling - 30 cents buys a good amount of security in this regard.) and unless previously damaged, there is nothing to wearout here in the middle.

I do not know if mod works but I believe it can't hurt but I'm not sure why. It is a last resort to mend a needed repair and/or to make a parts purchase.

Click to expand...

However, Mick(kettle738)'s Commando is an 850 MkIII which already has a positively-located double cotter pinned spindle (no central 1/4" bolt) therefore the Kegler conversion is unnecessary (I'm not exactly sure there would even be enough space to fit the Kegler clamps to the MkIII cradle tube?). Any apparent play in the MkIII S/A assembly should (at least, theoretically) occur between bushes and spindle.

http://www.oldbritts.com/1975_g16.html

Click to expand...

Darn, that MKIII stuff gets me everytime. Well, the info should apply the the other Commando owners.

it is a a necessary mod. you are one of the lucky ones IF your spindle was tight in the cradle. the only REAL support to the pin is at the sides of the cradle NOT the tube as it is a thin wall piece and BOTH parts are SOFT. the forces put on the pin hole are way more than the material can cope with as it is made and it stretches the bore egg shaped.

pvisseriii said:

I have had the split ring mod for years but after servicing my spindle last week, just a check, I question its necessity. When things are fitting proper, there is no play to take up.

Click to expand...

bill said:

it is a a necessary mod. you are one of the lucky ones IF your spindle was tight in the cradle. the only REAL support to the pin is at the sides of the cradle NOT the tube as it is a thin wall piece and BOTH parts are SOFT. the forces put on the pin hole are way more than the material can cope with as it is made and it stretches the bore egg shaped.

Click to expand...

+1 The tube is just too thin to try to anchor anything to it by itself. I cut the tube out and made a one piece part with thick sections for the bolts that are welded to the sides of the cradle. I think Steve did the same thing on his alloy swingarm. The load is distributed over a broad area of the cradle. It might be just as good to put together a set of collars with bolts to lock the spindle and braze or weld them to the inside of the cradle if one didn't want to cut the old tube out. Also just laying a bead over the original welds where the tube is attached to the cradle would shrink down the size of the hole some. It would buy some time anyway. The underlying problem is that the points carrying the load are so close together.

There is probably some considerable crush on the bushings when they are pressed into the swingarm. One can check the fit in the mounted bushings without running the spindle through all the way through, just check one side at a time. If they bind when when the spindle is run through all the way then the swingarm might be bent. It's not uncommon.

Usually the spindle is tipping inside cradle tube more the inside the bushes. As stated it may end up almost interference fit once fully assembled and nothing quite true/square. Collars spread loads over enough thin tube don't need back up to trap spindle from rocking or twisting. Takes a real close observation to see how much rear patch side motion is d/t swing arm vs the isolastic system pivoting on rear mount while moving side/side at front mount needed slack gap settings. If you grab top/bottom of rear tire and can't twist out of vertical line then most the side/side slack ain't in swing arm area. Btw there is over size OD spindle available but not over size bushes in case that gives any clue what next to spend on beside collars.

Thank you for the detailed replies, much appreciated......I think my best hope lies either in a 'crush' element to reduce clearance when the new bushes are fitted to the swing arm or that they may be less than perfectly aligned and hence remove their own free play, but to be honest I'm not holding my breath as they seem identical in all respects to the ones I removed.

The new bushes are currently marinading in SAE 90 and I've made a tool to press them home, hopefully incident free (the old ones came out easily and unmarked) ......if the new bushes are exactly the same I guess the next step will be an oversize spindle and getting them reamed......bit of a waste of a new set of bushes if it comes to that though...........but at least they seem cheap compared to typical Japanese parts.

Thanks for the input.............Mick........kettle738

With the MKIII, another place to check and could save time / money is the spindle cotter pins. It may be a case of the whole spindle assembly moving due to poorly located cotters. I have noticed on my spindle which is a modified system to accept taper bearings as per the photo.

http://farm8.staticflickr.com/7230/7304034482_243732bf11_z.jpg

I don't know that this story has any bearing (sure the pun is intended) but it has gotten me thinking. When I tore down my 850 the bushes were in very good condition but I removed them anyway because of preparing to paint the swingarm. The spindle was a nice tight fit until I drove the bushes out with a similar sized socket. The process compressed the end of the bush enough that it would no longer slide on to the spindle and would require honing if it were to be reused.

Doing this intentionally wouldn't be any worse than hoping misalignment might provide for any looseness. Both would be less than 100% contact for the bearing surface. It does make me wonder if figuring out a way to crimp, bash or mushroom out the bush in a more uniform fashion wouldn't be worth the time spent.

Russ

Only way to get a clean slip fit and nearly 100% even bush contact is line bore the swing arm with the bushes installed on the cradle. I"ve one 750 swing arm straightened and bored by Vernon of GT Enterprises frame fame and it passed the new spindle fine off cradle but never did once slipped around cradle so I gave up and trashed it. Got 850 swingarm and collars that allowed putting the over size spindle in then put on the collars and worked out stable and free swinging.

Well, I've just fitted the new bushes to the swinging arm, and to my total amazement the spindle is now a nice tight push fit, the slop has disappeared.

To be honest, I had zero faith in there being any tightening or reducing effect on the bushes simply by pressing them into the swing arm.....if they had been plastic then maybe, but you live and learn and the evidence is incontrovertible....the bushes were loose on the spindle before they were pressed in and now they are a tight sliding fit.

I feel I learned something new today, and I hope it may be of use to others......many thanks for the responses.

Mick.......kettle738.

"Usually the spindle is tipping inside cradle tube more the inside the bushes."

That was the case with my 850 so the collars completely eliminated the play. If the bushings are so loose on the spindle that there is actually "wobble" room then it would seem to me that either the spindle is worn due to no or improper lubricant being used or the new bushings are sized incorrectly. Both are possibilities.

As ya found out these bushes are not that sturdy and should be checked for ID roundness which can become distorted by processing, storage and handling. I've run into this on fork bushes that failed to slide over new stanchions, till I rounded them by light hammer rapping their OD while using the stanchion as the former. Didn't take much till they slipped sweetly as can be expected. This simple Commando sure teaches complexities of metal being an elastic malleable material. If ya want a bit deeper lesion on swing arm bush alignment and slack, ink the bushes ID and slip a dry spindle in there to see if the nice clearance fit is really only partial contact inside each of slightly tipped out of line bushes. The weakest stability area is the slop inside cradle tube and would be best if the spindle was part of the cradle, except for swing arm removal, but if kept lubed and mostly cradle stable, should not need another service in your life time.

I've come to believe the main reason for lube is to keep the spindle from rusting more than wearing. Them soft bushes don't stand a chance of bothering the extra hard spindle surface. I'd had two terrifically trapped spindles, one in constantly use up til I got it, pre-Peel and another that sat up in New Orleans coastal shop for over a decade, both got trapped by rust expansion, pre-Peel wore lips where rust ate up the hard layer, the other no wear lips just fused as one to the inside of the cradle tube, so that swing arm had to be cut off first before Bulldozer shop 30 ton press strained over 16 tons pressure to get it out. i gritted teeth on very well backed up cradle looking like a pie tin foldable, but sprung back square thankgoodness. Pre-Peel's swing arm got distorted by the severe pulling and pounding to get spindle out so even Vernon at GT Enterprises was not able to straighten to pass the spindle again, so had to trash it too.

Btw 140 grade gear lube = 40-50 grade engine oil. Thickest engine oil like for pre-war Harleys is 70 grade or weight, though the W means Winter grade not weight. Industrial cutting oil can be in this warm grease like thickness too.
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