Front fork jerking on acceleration and deceleration

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MichaelB said:
Did you ever get this sorted?
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Just started checking out the possibilities today. The axle is tight. The head steady is tight. How play is too much play in the swing arm? I was able to move it side to side less than 10 mm each way.
 
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Where is the play, just under 10mm sounds too much but is it the swing arm pin/bushes or too loose rear iso's. When you pull it back and forth look at those 2 areas and see where the play is.
 
I just read this reply from L.A.B on an older thread ...

"would improper isolastic adjustment allow me to manually rock the rear wheel slightly, side to side? I can physically feel the play when I do that.
Yes, it's possible, if the Isolastics are loose or the rubbers have deteriorated.
To check actual swingarm play you need to feel for movement between the swingarm and the cradle at the pivot."

I'm not certain the play is not from the rear iso's. I will check that next.
 
The difference between play in the swingarm-cradle vs iso's would be apparent, if you support the bike on the frame and lever the engine you'll be able to measure the iso clearance. A loose swingarm will show up as a "hinge" like feeling.
 
You can try holding Z plate with one hand and the tyre at the rear with the other and push and pull to the side repeatably. At the same time look at the swingarm next to the cradle and look for relative movement, then look at the cradle to rear iso end plates. Any relative movement should be evident to the eye and will show you where the wear is or a loose adjustment.
 
contours said:
I have it up on a jack now supported on the frame. When you say "lever" you mean bear down on it?
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I use a 1" dowel rod, find a suitable area where you can wedge it between the frame and cradle and use it as a lever. This is easier if the headsteady is disconnected as it will prevent a proper clearance check on cradle ISOs.

If your swingarm has 10mm play as you described that's a problem. I would remove the rear wheel and detach the lower shock bolts to verify this.
 
Thanks for the help guys. I won't ride it again until I know what's going on.

Gotta get back to work for now, but I'll report back the next chance I get. (I'm also dealing with a flat rear tire on my wife's Indian Scout so that's going take priority).
 
10mm is a LOT. MKIII with taper keyed swing arm shaft.....
Iso play or swing arm bushes.
 
So far it's hard to tell whether the play is really in the swingarm. But the side-to-side is accompanied by a creaking sound which makes me suspicious.
 
You know...This all sounds like the 'Commando Twitch' to me. Even prior to stowing mine years ago it had developed an anomaly where I thought it was suspension, then isolastics, & numerous other BS. After the rebirth I had replaced all of that and got to piddling after the twitch increased causing me great concern. Well, put it up on the center stand giving the rear wheel some side to side tugs noticing swingarm play. Really not all that much to the eye, but you could feel the movement.
Put the gauges to the rear isolastics and they were good, and then cleaned up everything well exposing noticeable movement at swingarm connection. Pulled apart & did visual of bushings. Found them badly worn & ordered new. Once installed & properly lubed anomaly has vanished. I guess what I'm trying to say is that the way our Commando's are made worn items may manifest themselves in many ways leading us a merry chase. At times I had believed the front wheel or steering head bearings were toast.
Everyday with my Norton is a new adventure, as a matter of fact it's the most interesting motorcycle I've ever owned.....or been owned by. Never figured out which.
 
jbruney said:
You know...This all sounds like the 'Commando Twitch' to me. Even prior to stowing mine years ago it had developed an anomaly where I thought it was suspension, then isolastics, & numerous other BS. After the rebirth I had replaced all of that and got to piddling after the twitch increased causing me great concern. Well, put it up on the center stand giving the rear wheel some side to side tugs noticing swingarm play. Really not all that much to the eye, but you could feel the movement.
Put the gauges to the rear isolastics and they were good, and then cleaned up everything well exposing noticeable movement at swingarm connection. Pulled apart & did visual of bushings. Found them badly worn & ordered new. Once installed & properly lubed anomaly has vanished. I guess what I'm trying to say is that the way our Commando's are made worn items may manifest themselves in many ways leading us a merry chase. At times I had believed the front wheel or steering head bearings were toast.
Everyday with my Norton is a new adventure, as a matter of fact it's the most interesting motorcycle I've ever owned.....or been owned by. Never figured out which.
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Did you also put some clamps on?
 
I take it you're referring to the split clamps everyone was using on the swing arm. If so the answer is ...Nope. Put it back as it came apart. I have a habit of doing that on jobs I don't particularly enjoy.
While I'm on that I believe there's another on the near horizon with an unusual noise which began coming from near my timing case intermittently this afternoon vexing me most dastardly. It's not Christmas or my birthday so I don't want to open unwanted presents.
 
Since the Iso's were fettled, I would suspect the front, if that's where the movement seems to be emanating from. It's half the width of the rear yet takes most of the stress.
 
jbruney said:
Everyday with my Norton is a new adventure, as a matter of fact it's the most interesting motorcycle I've ever owned.....or been owned by. Never figured out which.
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Well put! It's interesting that it took until now (nine years) for this problem to become so conspicuous. Since the first time I rode it I felt the steering was a bit loose. But never having ridden a Commando before I assumed it was innate.
 
contours said:
Well put! It's interesting that it took until now (nine years) for this problem to become so conspicuous. Since the first time I rode it I felt the steering was a bit loose. But never having ridden a Commando before I assumed it was innate.
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A proper Commando should feel tight and solid on the road. People think because of the isolastics it should feel rubbery but that not the truth.
 
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