Improved swingarm

[fredintoon]

This comment by Peanut showed up in my "rant" string:-
I guess a decent swingarm would be a lightweight one with integral strengthening and taper metal bearings rather than the plastic oem ones

and I thought a reply to it would be more appropriate here.
While building a high strength lightweight XS650 swingarm may be beyond the average shade tree mechanic's skill set, improving the OEM plastic bushing set up is not.
Peanut's proposed Timkens will work but they ain't cheap to buy or easy to install.
Plain bushings are the simplest way to pivot a swingarm so long as it's done right.
This concept materialized in another string a while back.
Problem with the OEM pivot is only partially that the plastic bushings wear out.
T'other part is that the swingarm throughbolt don't always keep the bearing sleeve locked into the frame.
The bearing sleeve then starts to turn with the swingarm so that the actual bearing is between the bearing sleeve's bore and the throughbolt's outer diameter.
This is a steel on steel bearing and a slack fit besides. Not a good thing.
The fix that evolved was this:-
Replace the bearing sleeve with a same size solid bar bored each end 16mm diameter x 20mm deep and tapped M16 x 25mm deep at the end of the plain bore.
Install bronze swingarm bushings and fit a grease fitting in the swingarm cross tube.
Grind off the frame's swingarm throughbolt anti-rotation block.
Assemble the swingarm in the frame using M16 bolts long enough that their plain shanks fit into the bearing shaft's plain bores but short enough that their threads don't bottom out before they tighten the bearing shaft into the frame. (this may need some hacksaw work on the bolts.)
Reef the bolts up tight. Tabwashers, lockwashers, Loctite, you choose.

 

[joebgd]

What wud the m16 bolts thread 2. I dont follow the thing 100% . Mayb a scetch will help.

 

[racerdave]

What wud the m16 bolts thread 2. I dont follow the thing 100% . Mayb a scetch will help.

From the first post " solid bar bored each end 16mm diameter x 20mm deep and tapped M16 x 25mm deep at the end of the plain bore. "

 

[5twins]

The only part I don't get is how you can tap 25mm deep into a hole that's only 20mm deep. Must be some of that "machinist's magic" I'm not familiar with, lol.

 

[racerdave]

I thought the solid bar goes side to side?

 

[fredintoon]

Gawdelpus.
what you think you understood was not what I meant to say
OK then:-
Mount the solid pin in a lathe and drill it 45mm deep with an M16 tapping drill (that's about a 9/16" drill size, but you go look it up.)
Then open the hole out to 16mm but only go 20mm deep with that.
Finally, tap the smaller, deeper hole M16 as far down as the tap will go.
Then do the same to t'other end.
The design's plain counterbore and longer bolt is so the shear forces are taken by the bolt's plain shank rather than by it's threaded portion.

 

[Uncle Bryan]

I think even with that little bit of material and machine work that you have already exceded the cost of a needle bearing kit

 

[Fings369]

This is gonna sound stupid, but here goes....

Assuming these plastic bushings fail, or are faulty, how fun and/or what happens when they do. Just warping of the inners and metal on metal such, or is this something I should consider being proactive about and get the brass ones for now??

Thanks!

 

[joebgd]

I would say for regular transportation riding the original bushings are fine. I did get the brass ones but I think the originals were fine and I've heard people have them with no problems. It def didn't hurt my bike tho The only thing I wish I didn't do was change the steering bearings. little off topic but if your asking ab swing arm bushings steering might also b on the mind. If the swing arm bushings start to go you will more than likely feel the rear wobble.

 

[fredintoon]

Uncle Bryan, depends if you have a "Bro with lathe" or not.
Fings, the handling gets imprecise as the bearings wear. It's not so much the plastic bushings crapping out as it is that the frame's grip on the bearing sleeve lets go and the sleeve starts turning with the swingarm.
joebgd, the bronze bushings are an upgrade but only if the bearing sleeve is properly locked into the frame.
And the serious hazard is the stock throughbolt's M14 threaded end breaking off.
This lets the throughbolt fall out on the street which in turn can lock up the rear wheel.
Happened twice on my Heritage.
First failure was at highway speed. Lucky my son was riding and all that dirt bike experience let him ride the bike to a standstill, locked rear wheel and all.
Installed a spare pivot bolt and that one failed too. Lucky I spotted it half way out as I was rolling the bike down the driveway because I'd most likely have crashed the thing.

 

[weekendrider]

If the "pop" of the bolt breaking doesn't get your attention the bikes reaction to the right side separation of the frame and swingarm should. The bike seems to raise and lower like you got another 40hp of torque all of a sudden. And this is long before the bolt comes all the way out. I did a "can you guess" thread in the lounge a couple of years ago on this.

Fings369 put the bike on the center stand or blocks to get the back wheel off the ground. Grab the wheel at the at the 3 o'clock (looking at it from the left side) and wiggle the tire back and forth to check the bushings. There is a tolerance but you'll have to look it up yourself.
Back on the rider site Yamaman brought up the fact that the originals lasted 20-25 years and what is wrong with that? Considering the cost difference between OEM and the brass nothing is wrong with OEM. Keep the swingarm greased and you won't need anything more than channel locks to get them out the next time. . . if you live long enough and ride enough miles to wear them out.