Anybody ever try this?

azman857

'80 XS 650SG Rider
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I've wondered this for a while. The stepped swingarm bolt we have(or had for those who upgraded). Instead of enlarging the hole for the unstepped bolt from a Suzi, Why not bore and thread the original bolt after the stepped, threaded portion is removed(sawed or machined) off? Use a bolt of same diameter and fine pitch and lock threaded.Gets rid of the stress point and no need to enlarge the hole in the frame. If there is a way to get that hole off centered while drilling, I would probably find that way. Maybe others have done that action and end up with the swingarm being un-centered.
 
I don't know...Wouldn't have to be too long. 20mm would be more than enough. Your replacing the nut with a bolt basicly. Lock washer would be a good idea too. Not much grip area (unthreaded portion)would be needed. Just enough for the lockwasher, frame and thread length. 20-30 mm?
 
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Someone on here had a similar idea. I can't find the thread.
But honestly, I'd spend the $29 and buy an unstepped one from 650 central and call it a day.
 
The frame is the same size all the way through, no mods needed to use a larger thread pivot bolt. The drilled hole might weaken the bolt at the shear stress point, bushing, frame junction. A broken thread does not cause immediate failure, it allows the pivot bolt to slide out to the left eventually letting one side of the swing arm frame joint drop. At that point the rider probably starts to notice unusual handling. If the frame is too wide at the pivot, shim the gap, don't go all gorilla sucking the frame together with the nut, which creates alignment problems also. As just mentioned in another thread more than 40 bikes through here I have yet to see a broken thread, it happens, but it ain't common!
 
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At that point the rider probably starts to notice unusual handling.
Yes, yes it does. My experience was it was like you had gained 200 hp of torque as it would raise and lower accordingly with acceleration/deceleration.
I didn't find it all that difficult to hold it in place with my left heel till I reached my destination.
 
There is not supposed to be a lot of torque on that bolt. After this many years, what are the chances nobody ever grunted on it?
 
I think over-tightening is probably the main reason they fail. I've been into quite a few of these assemblies as well and like Gary, never found a bad bolt. It took some searching but I was finally able to locate a torque spec for this given as a range instead of just a single value. It is 36.2-58 ft/lbs.
Tighten the nut just enough, and in that range, so that the bare arm barely drops by it's own weight and I think you'll be fine.
 
I think over-tightening is probably the main reason they fail. I've been into quite a few of these assemblies as well and like Gary, never found a bad bolt. It took some searching but I was finally able to locate a torque spec for this given as a range instead of just a single value. It is 36.2-58 ft/lbs.
Tighten the nut just enough, and in that range, so that the bare arm barely drops by it's own weight and I think you'll be fine.

Hi 5Twins,
I can't agree with that. Yes, that's what Yamaha recommends but it's wrong, just like their pathetic swingarm pivot design.
If you don't tighten the throughbolt until your eyes cross and you break wind the swingarm bearing sleeve won't stay locked in place.
Instead it will start turning with the swingarm so that the bearing ain't between the stock plastic or the replacement bronze bushings
and the swingarm bearing sleeve as the design intended. The new loose steel on steel bearing will be between the unpolished bore
of the bearing sleeve and the O.D. of the throughbolt.
Dropping under it's own weight is a function of setting up the correct swingarm side clearance. If you can control the free drop by reefing
the throughbolt tighter, the swingarm has been set up with insufficient sideplay.
The quick fix for this is an M16-ended throughbolt that can be done up enough to lock the bearing sleeve from turning without it's end fatiguing off.
 
When I got my 82 a PO tried to fix the broken pivot bolt by drilling and threading the bolt. A bad Idea. It wouldn't tighten enough to hold the pivot tube.
Even a properly shimmed pivot tube needs proper torque to squeeze the frame enough to hold position as 5twins mentioned. I found the swing arm on the ones I have done need about 50 Ft/lbs. of torque to hold position. This is with just the swing arm installed. It may vary a bit.
Leo
 
Hummmm on every other bike I've had the swing arm off You tighten it till it's snug Not over tighten it till the nut sheers off ! so who' right here ?
logic would say if the frame has to be squeezed that hard to Lock the bushings in place your doing something wrong ! perhaps it is time for shims on either side of the swing arm to make up that distance.
I am assuming the idea of the tight bolt is to hold the bushings in place.... then why did they put Plastic ones in at the factory ? plastic will mushroom
and bloom outward..... no tight bolt in the world will make plastic work like that..... so it has to be snug Not tight as an end results !
the rear swing arm has to move freely if your Ronching down on the bolt so hard you are bending the frame into the rear swing arm your defeeting the purpose of the swingarm ! .....
I have not ventured into the Bronze bushing ariena yet.... but hope to soon as I dislike the idea of plastic bushings and a bolt that has failed even once while riding needs to be replaced on every other bike in the world ! when I do change the bushings I will tighten the bolt to where the swing arm just barely falls under it's own weight and test for side to side movement there should be NONE
doesn't this sound like a sainer approach then tightening the bolt to 50 to 75ft lbs and hope it doesn't pop while riding ?
....
Bob....
 
Bob, the bushing doesn't get pinched, the pivot tube does. The tube and bolt do not move, the bushings turn around the locked pivot tube. That is why it is esential to have a very small amount of tube exposed on either side of the bushings and why so many are having trouble with after market tubes. Some are too short and the bushing or swingarm must have material removed to facilitate proper fitment.
 
Hi 5Twins,
I can't agree with that. Yes, that's what Yamaha recommends but it's wrong, just like their pathetic swingarm pivot design.
If you don't tighten the throughbolt until your eyes cross and you break wind the swingarm bearing sleeve won't stay locked in place.
Instead it will start turning with the swingarm so that the bearing ain't between the stock plastic or the replacement bronze bushings
and the swingarm bearing sleeve as the design intended. The new loose steel on steel bearing will be between the unpolished bore
of the bearing sleeve and the O.D. of the throughbolt.
Dropping under it's own weight is a function of setting up the correct swingarm side clearance. If you can control the free drop by reefing
the throughbolt tighter, the swingarm has been set up with insufficient sideplay.
The quick fix for this is an M16-ended throughbolt that can be done up enough to lock the bearing sleeve from turning without it's end fatiguing off.

Well Fred I gotta give you that the "quick fix" is using a bigger (hammer) thread to bend the effing frame into submission.
I'm pretty sure by design the swing arm assembly should be a push fit between the frame bushings, then moderate torque on the bolt and you're done. This bike is old school, swing arm pivot design has come a long away since 1969. The XS was not the flagship by the time the 447 frames were tooled, the jigging and tooling saw a lot of use. (wore out) Not always but often enough that I've seen a few, the frame bushings are too far apart to capture the swing arm without bending the sides together. If the factory did this, the bolt may have been overstressed from the get go. If they didn't, and the frame was wide, the bike may have had poor handling from the get go. The IMHO proper technique is to use (3/4" from the hardware store work fine) machine bushing(s) to take up any excess space, then tighten the bolt with MODERATE force. LOOK at this area of the frame when the swing arm is out. There is a welded cross brace just in front of the swing arm mounts. You force those mounts together you HAVE to bend them out of alignment. putting bending stress on the bolt which will wear the bushings oval in short time, plastic OR bronze.
Please note: this is a COMPLETELY separate deal from setting the swing arm sleeve, bushing end clearance, which also needs to be done, checked during reassembly. it is not unusual to find aftermarket bushings that have end shoulders that are too thick (or powdercoat on the swingarm) so that it is not possible to properly set the sleeve end clearance.
Go through this thread it lays out the typical swing arm problems and correct assembly. This is about where I got the proper shimming procedure hammered into my head. To this day good old pregrid did one of the best build threads I have ever seen! (the result was outstanding also)
 
Littlebill31 :
OK gotcha' I went through gggGary's link and had all my questions answered.....
one last thing ... you could always make a shim just for the inner tube if it's still not long enough rather than crush the frame together ....
as long as this little shim it's centered on the bolt it won't chew on the bushings.
the exploded view cures so many questions,..... we should have one for every technical question ! LOL
....
gggGary ! you used a 3/4" bolt from the hardware store in your swing arm ? how long was it ? and was it grade 8 ?
I suppose you cut your own bushings then ? or did you modify Hardware store bushings ? sounds like a really cheap way to do an expensive job to me ! LOL
Bob..........
 
NO! 3/4" machine shims, like washers but thinner and ground flat. Use these IF there is space between the properly shimmed and assembled swing arm and the frame.
 
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