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Discussion Starter · #1 ·
I was not sure where to post this. I am figuring it may be mechanical, or mental.

I will try my best to explain. One caveat. I am a fairly new rider for just a few months. It could just be my inexperience.

This issue does not happen often, but it has happened in the same part of several roads- but not always. It seems to occur when going through a fairly slow sweeping left hand curve. I sense a shimmy or almost as if the back wheel has lost traction. I have noticed a similar sensation when driving along a crack in the road where two sections of asphalt have been joined. The feeling is that a quick correction is needed and then it is gone before I have had a chance to do anything.

My first thought was the swing arm bushing. I checked it several times up on the center stand. There is no give whatsoever to the left or right. Same with the front and rear wheel bearings.

Any insight is appreciated. Am I just overreacting to a normal situation?

jon
 

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Maybe it's possible your rear wheel chain adjusters are out of true - we generally like to have both wheels pointing in the same direction.

What about your tires, how old??
 

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Discussion Starter · #3 ·
Tires are good. I will check the chain adjusters, although I was careful to set them back properly when I had the chain and front sprocket off to change some oil seals a few weeks ago.
 

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As I was reading your description of the problem, it sounded exactly the issue I had with my KZ. Turned out it was the swingarm bearings as well as the rear wheel bearings. However, you have already ruled them out. Check to make sure the wheel is true like Bill mentioned. Could also be the 30 year old rear suspension, maybe time to swap them out. I know on my '78 KZ they were not the best in the corners. I got used to them, but still should have been replaced.
 

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I get the same sort of sensation on my Yamaha and its always when the tyres have lost their profile and are developing a flat around the centre. Problem caused by lots of main road driving. New tyres always cures it.
 

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Also check that the swing arm bolt is tight.
 

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Discussion Starter · #7 ·
Thank you all for the responses. At least I know I am not nuts. At least not in this regard. I just checked and the right chain adjuster was about 1/2 to 3/4 turn off from the left. Also the back tire does have a bit of a flatness around the middle. Otherwise the treads are good. I can see how that can cause an issue. I will start checking the tire threads for recommendations.

I can check the swingarm bolt later.
I am wondering if I it only happened on left turns because they are not as tight a turn.
 

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Well, the "uneasiness" when on a lapover of asphalt is actually pretty normal - the twitching in a left hand sweeper is not.

Many times the little chain adjuster marks on the swingarm are NOT that accurate. On my 450, one side is almost a whole mark off, relative to the other side.
I found that out by using a long, straight 2x4 (are there even straight 2x4's anymore??).
 

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Grab hold of the back end and see if you can detect any movement in it when pushing from side to side. (make sure that the bike can't fall)
It never hurts to check if there is no mechanical movement or maladjustment of the rear end.
If all else fails have the shocks been checked over?
I still wonder about the tyres though even if they look ok, if they have been in the sun, the UV will degrade the compound to the exent that it will exhibit those charectistics.
 

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To be SURE your rear wheel is "true", MEASURE from center of swingarm pivot to center of axle on both sides.... They MUST be identical....
 

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So far, great suggestions, check them all out.

Also, do your tires have an aggressive tread? Or are they at all under-inflated? I've had my rear tire get "squirrely" on me for either reason in turns, and, for some reason, I am a lot more comfortable making left-hand turns so I tend to lean over more and hammer the throttle a bit more coming out of them, so it is more prominent then. Just a thought.
 

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Got money on the swing arm bushing, just grab your tire and push it side to side and you wil notice right away if its good. My brass bushings should arrive today or the next to fix the same feeling on mine.
 

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Discussion Starter · #13 ·
Actually the bike is down to the frame right now for a good cleaning and paint. When I removed the swingarm, the collar seems to have a tight fit in the bushings. Very little, if any movement at all. I did not have any lateral movement when the bike was assemble when trying to move the rear wheel left to right.

Can the collar to bushing clearance be measured and what would be the tolerances? I have a friend that is a mechanic for a Nascar team so he has access to all kinds of good equipment and tools.

As far as the tires go, as stated earlier, there is a slight flattening across the middle of the tire. I think that may be the culprit as I turn, I may be rolling on the 'edges'. If that makes any sense.
 

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You never said how old your tires actually are, you just said they were "good".
If they're over 6 years old or so, I wouldn't even ride on them personally.
 

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Discussion Starter · #15 ·
tbpmusic said:
You never said how old your tires actually are, you just said they were "good".
If they're over 6 years old or so, I wouldn't even ride on them personally.
The tires are 2 and 3 years old. Date codes are 2007 and 2008. And I will backpedal on the 'good' statement based on the flattening that I described.
 

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drones76 said:
tbpmusic said:
You never said how old your tires actually are, you just said they were "good".
If they're over 6 years old or so, I wouldn't even ride on them personally.
The tires are 2 and 3 years old. Date codes are 2007 and 2008. And I will backpedal on the 'good' statement based on the flattening that I described.

Maybe they were run under-inflated for a while......
 

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here are a few other things you can try.. how is your chain? over tight and or binding / kinking or worn sprockets can have profound effects on the suspension. I made the mistake once on my triumph, contributed to a low side in a greasy traffic circle, hit a bump and the tight chain loaded up the rear suspension and it lost it. thank you aerostitch!

look at your sprockets, the teeth should be very symmetrical. the chain should not have any tight links and when held out against the grain (pins perpendicular to the floor) it should not sag more than a few inches. Soaking in diesel will usually fix a few rusty links, chains are cheap though, and a failure will likely be catastrophic.

The other item that can give you a loose rear feeling is a front end issue. how are your steering head bearings? loose, lumpy, gritty? grab the forks by the bottoms and feel for any play, as with the swing arm there should be none. the forks should fall to one side or the other easily when unloaded and not feel rough or gritty. tapered roller bearings are a great upgrade for $40

your rims could have loose spokes or be out of round/ warped. Clamp a piece of wire on the frame/ fork near the rim and spin watching for any movement relative to your indicator.. not necessary to be perfect, but should be very minor like a couple millimeters with a little practice your eye can detect a couple thousands difference. The spokes should all make a similar tone when struck with a small wrench ding, ding, ding, thunk
 

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Discussion Starter · #18 ·
ihatespeed said:
here are a few other things you can try.. how is your chain? over tight and or binding / kinking or worn sprockets can have profound effects on the suspension. I made the mistake once on my triumph, contributed to a low side in a greasy traffic circle, hit a bump and the tight chain loaded up the rear suspension and it lost it. thank you aerostitch!

look at your sprockets, the teeth should be very symmetrical. the chain should not have any tight links and when held out against the grain (pins perpendicular to the floor) it should not sag more than a few inches. Soaking in diesel will usually fix a few rusty links, chains are cheap though, and a failure will likely be catastrophic. I have checked the sprockets and they are symmetrical. I have not checked the chain. It is off the bike and I can check tonight.

The other item that can give you a loose rear feeling is a front end issue. how are your steering head bearings? loose, lumpy, gritty? grab the forks by the bottoms and feel for any play, as with the swing arm there should be none. the forks should fall to one side or the other easily when unloaded and not feel rough or gritty. tapered roller bearings are a great upgrade for $40 I have a set of All Balls tapereds on the shelf waiting for reassembly. When I removed the old bearing races, there were detents in them from the ball bearings. Figured it was worth going with the tapered at this point.

your rims could have loose spokes or be out of round/ warped. Clamp a piece of wire on the frame/ fork near the rim and spin watching for any movement relative to your indicator.. not necessary to be perfect, but should be very minor like a couple millimeters with a little practice your eye can detect a couple thousands difference. The spokes should all make a similar tone when struck with a small wrench ding, ding, ding, thunk
I have done the tone check on the spokes. They seemed ok (although my wife thinks I am tone deaf). I will recheck tonight. I cannot check the spin because it is apart now.

Thank you all for the suggestions. I think new rubber, bearings and everything in adjustment and all should be well. I may also get the bronze bushings.
 

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Forgot one other thing, what are you used to riding? 40 year old bike with probably 40 year old shocks, bushings, bearings, spokes, tires;that cumulatively is about 6" of slop in the rear :lol: Maybe it's center stand trying to right you back up. Good luck, you seem like you got a good head for this stuff.
 

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Discussion Starter · #20 ·
Overdue followup. I put a new tire on the back last night. I took it to the two places in my neighborhood that I can usually create the odd feeling. Went through the turns several times. So far so good.
 
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