Swing Arm Bushes

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Dukepaul

Dukepaul

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Hi,
This is my first post so be gentle with me.

Inspired by the Covid lockdown am building a café racer utilising a bitsa commando I have had lying in the back of my garage for 30 years, its a 1971 750 commando but bits of other stuff as well.

The engine, gearbox, forks and wheels have all been stripped and rebuilt, I am just waiting for the tank and seat I have ordered from Tab II Classics to be delivered so as I can finish any frame mods before sending it for powder coating and this is where I need help (I have already searched the forum but couldn't find an answer)

The swing arm is off a later model (I think an 850) because it has the shorter spindle and is recessed to take the Welsh plugs and the shorter 30mm bushes and this is where I need help, the current spindle has to be replaced and when I measured it up it is an 0.005" oversize one which is no problem because I see these are readily available, but what I cant find are any bushes that are also 0.005" oversize to match the oversize spindle, or am I missing something here?

Thanks in advance for any guidance.

Cheers
Paul
 
Welcome @Dukepaul,

Typically it is not the bushes that are worn, but the root tube welded in the transmission cradle that gets wallowed out. Make sure to check that fit, and deal with a proper fixing (dual clamps or pins, etc.). www.OldBritts.com should have undersize bushings, not sure who has them in the UK, but would assume Andover Norton does...

-GrandPaul

(is there an echo in here?)
 
I was told that the bushes are very hard wearing and normally don't need to be changed. I had a badly corroded central pin which I had to hammer out. I bought a new pin and bushes and tried the new pin for size without removing the original bushes it was a tight sliding fit. The bike is assembled and there is no play.
 
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Hi
Check and fix the area on the g'box craddle where the o ring outside the bush wears this surface and causes another point for oil to leak from the swingarm. Also a good idea is to also shim the bushes to take out the end to end play that exists between the swingarm bushes and the gearbox craddle this requires a bit of fiddling to get adjusted. Consider using the newer bushes made of materials such as Ertalyte TX ( polyethylene terephthallate )that do not require lubrication , there are a couple of sellers on this forum .
 
gortnipper said:
If you have to replace the spindle and bushes, why not just get standard replacements?

Also, do the Kegler mod.
Click to expand...

He can't really use standard parts unless he renews the gearbox cradle because the pin is plus 5 thou
Hence the tube in the cradle will be 5 thou too large
 
I have replaced just the pin before when it was worn
The bushes were perfect
 
There have been comments about powder coating on this forum. I did powder coat mine but when I put the tank on , I didn't add enough padding under the rear so it rubbed to powder coat off. The comments were along the way that if you wear your coating off, and don't fix it, water will get under it and cause rusting. Two pot paint is just as hard but easier to re apply. The old rattle gun job is quicker and easier and also far easier to patch up. Your Call.

As for the swing arm pin, it was never designed to be tight. [ just another build f/up included in the build ]. The manual specified an easy push fit. That's bullshit. It should be a tight fit or it will flog out like they all do. The tube it goes through, is only a spacer and not made of thick enough material to be strong enough, hence the Kegler clamp mod. As for that locating 1/4 UNF bolt. That's a laugh.

Dereck
 
Well then, you may as well do the Kenny Dreer "Big Bearing" swingarm spindle fix that I modified ever so slightly by using Commando sealed steering neck bearings... (I still have materials to do 1 or 2 more)

CdoBigBrg.JPG


(don't worry I trimmed down the left side pinch bolt to clear the transmission case)

Never lube again!
 
baz said:
He can't really use standard parts unless he renews the gearbox cradle because the pin is plus 5 thou
Hence the tube in the cradle will be 5 thou too large
Click to expand...

Yes this is exactly the case, it seems I will just have to get some standard bore bushes and get them machined to suit the oversize shaft.
 
Dukepaul said:
I will just have to get some standard bore bushes and get them machined to suit the oversize shaft.
Click to expand...

The bushes are sintered ie oilite, they are designed so the pockets or pores between the bronze particles fill with oil and act as a lubrication reservoir. Who ever you ask to machine them must use a very sharp cutter, a dull edged cutter will smear the surface and close off the pores from the oil.
 
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kommando said:
The bushes are sintered ie oilite, they are designed so the pockets or pores between the bronze particles fill with oil and act as a lubrication reservoir. Who ever you ask to machine them must use a very sharp cutter, a dull edged cutter will smear the surface and close off the pores from the oil.
Click to expand...

Yes good point, thanks....
 
why not just try a new 5 thou oversized pin in your existing bushes first?
 
Thanks to everyone who has commented, I think my final solution will be to use a +5 thou oversize spindle and get it machined down on each end to suit standard bushes, that way I don't affect the oilite material, and also fit a kegler kit and hopefully that will fix it all.....
 
Dukepaul said:
Thanks to everyone who has commented, I think my final solution will be to use a +5 thou oversize spindle and get it machined down on each end to suit standard bushes, that way I don't affect the oilite material, and also fit a kegler kit and hopefully that will fix it all.....
Click to expand...
You can't do that
You won't be able to put the pin in !
 
Maybe look for another cradle
Or buy the 5thou oversized pin and std bushes
And get a machine shop to machine the bushes for you
 
Obtain a new tube from AN and get this welded in....it doesn't require any reaming, just cutting out/welding in & filing flush
 
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