1975 Mk. III Handlebar shake-speed wobble.

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concours said:
Here's my hat in the ring... brand new iso's, set at .005", new Avon's 100/90-19 36PSIF & 42PSIR, fresh swing arm bushes and clamp mod. High speed wobble from 80 on up to 110. Head bearings are good.

1. Tire pressure at or around 26psi? 36/42 WAY too high. If concerned, bring them down 4 psi at a time. My Avon Roadriders are at 26 front and read and 105mph was oh so fine on mine. I have done 90 steadily lately with NO issues.

2. Wheel alignment, straight edge along the front to rear wheel? It 2 different size tires, then another procedure will be needed. Adjust at rear wheel adjusters.

3. Pull tank and loosen head stready bolt at the head. Sit on the bike off the stands and re-tighten with your weight on it.
 
pvisseriii said:
concours said:
Here's my hat in the ring... brand new iso's, set at .005", new Avon's 100/90-19 36PSIF & 42PSIR, fresh swing arm bushes and clamp mod. High speed wobble from 80 on up to 110. Head bearings are good.

1. Tire pressure at or around 26psi? 36/42 WAY too high. If concerned, bring them down 4 psi at a time. My Avon Roadriders are at 26 front and read and 105mph was oh so fine on mine. I have done 90 steadily lately with NO issues.

2. Wheel alignment, straight edge along the front to rear wheel? It 2 different size tires, then another procedure will be needed. Adjust at rear wheel adjusters.

3. Pull tank and loosen head stready bolt at the head. Sit on the bike off the stands and re-tighten with your weight on it.

Rider weight?
 
concours said:
Rider weight?

Yes. It makes a difference on how that headsteady settles in with the riders weight on it. With the fasteners loose, move around and watch to see it settle. Feel it comfortably sitting and snug them up.

I am not saying that this will fix your issue, but it will get things better balanced with in the mounting system. That is to say that it sure can't hurt.

How is the offset on the front rim?
 
pvisseriii said:
Yes. It make sa difference on how that headsteady settles in with the riders weight on it. With the fasteners loose, move around and watch to see it settle. Feel it comfortably sitting and snug them up.
I'm going to disagree here. I've thought about it in my feeble old brain, and I tried this sitting procedure also. I didn't notice any difference in how the headsteady reacts nor how the iso units sit. If you think about it, all you are doing is putting weight on the frame when you sit on the seat, even if you get your feet off the ground and on the pegs. It doesn't change anything with the way the engine still sits with respect to the headsteady nor in the iso's (the frame), it's the same engine weight in the frame whether you have weight on the frame or not.

What will make a difference is if you jack the engine up with a floor jack and center the isos in their bushings and then tighten the head steady, but I actually think it made it worse on mine. I was trying to reproduce the MKIII spring effect.

I'm sure I'll get heat about this, I wave my right to further consecutive interpretation.

Dave
69S
 
Can't tell a thing about isolastic handling until two fresh tires on and aired to best effect, ie: least effort to work forks. I like 2 PSI less in front about no matter the baseline. 26 PSI rear gets a bit distorted squirrelkly to me if pressing traction leans, but feels wonderful short of stupid level loads. There should be no need of steering damper and no high speed wobble worry.

If ya look at the head steady rubbers you see if they are in a bit of skewed bind pre-load, so bash bend drill grind and spacer the plates and cushions till neutral. I can see not difference with me on or off bike to set this up. If in a bit of a bind it tends to transmit buzzing intermittently on leans or wind gust side load. For a bit more smooth I waist-ed Trixie's like I do the muffler mounts. Only want the compression of rubber not its skew resistance.

BTW the harder the tires aired the more solid stable base the iso's can work against so smooths out nicer but does make rough roads jarring. HIghest I went so far on tri-linked Peel was 58 rear 56 front and just felt better and better like an ice skater not clunky locomotive stuck on its loose fastened rails. Bob Patton stuffs 6 big doughnuts in his rear iso, i only put in 4 so far. With rod links can open gaps up to factory or even a bit looser but can get too loose so sloppy handling felt again. If you ever jump a Cdo the annoying vibes
hit until tires land on terra firma again. I've had enough blow outs now to realize instantly whats happened when vibes suddenly felt as bike unspported drops onto rim to get smoother again. No squirely sense if going straight ahead though, so can catch ya out if next move is a fling over or just a lane change, whooweeeepooopoooo.

Oh yeah the first lesion in how to barrel roll a cycle is to have rear tire come off rim at hyw speed.
 
pvisseriii said:
concours said:
Rider weight?

Yes. It makes a difference on how that headsteady settles in with the riders weight on it. With the fasteners loose, move around and watch to see it settle. Feel it comfortably sitting and snug them up.

I am not saying that this will fix your issue, but it will get things better balanced with in the mounting system. That is to say that it sure can't hurt.

How is the offset on the front rim?

Front rim offset is as she came from the factory. I observed it when changing tires, but didn't attempt to measure it.
 
DogT said:
I'm going to disagree here. I've thought about it in my feeble old brain, and I tried this sitting procedure also. I didn't notice any difference in how the headsteady reacts nor how the iso units sit. If you think about it, all you are doing is putting weight on the frame when you sit on the seat, even if you get your feet off the ground and on the pegs. It doesn't change anything with the way the engine still sits with respect to the headsteady nor in the iso's (the frame), it's the same engine weight in the frame whether you have weight on the frame or not.
This may make some sence but your not saying that it's a bad thing , are you? I will not disagree with you that it may not make any difference but these headsteady mounts are slotted for a reason. For me, I like it setup as if I am actually ride it.

What will make a difference is if you jack the engine up with a floor jack and center the isos in their bushings and then tighten the head steady, but I actually think it made it worse on mine. I was trying to reproduce the MKIII spring effect.
Well, you said it didn't work for you but I do not see how this would replicate an actual riding condition. A good state for adjustment, yes. Going down the road, they just don't ride in the center.

I'm sure I'll get heat about this, I wave my right to further consecutive interpretation.
No heat, just a good discussion.
Just to be clear here, I am only talking about the three bolt into the head.

Ya know, were just trying to get this guy going down the road safely at a high rate of speed.
 
Just stick fingers on either side of tire and swing arm and diddle to same-ness and all set to go w/o offset blocks to compensate straight edges for the rim widths or marks on floor or strings and other laughable devices that aren't carried with you for flats away from home and hearth.
I bet no one can even feel the misalignment if tire was skewed almost to touch the swing arm. I've tested this, but what do I know. Some rear rims are off set to one side 3/8", undetectable but trying to line up fender tire and rear loop all at once. Not saying don't aim for prefect but don't sweat it either. Tire wear is the most important issue here, next to sprocket chain wear alignment that is.
 
Oh my oh my oh my. After Bob Patton rear, Bryan Tyree front and my top link, combined, with fork mods, the world is now dived into all the bikes that can and will weave and wobble and those one in a row that simply can not, will not miss behave. I do not speculate One Iota on this so only feel so sorry for what you all are missing out on. Any and all the stuff in the aritcle and video apply to all other bikes but one.

I've a good gone through Trixie Combat that I've kept as factory issued with minor mods to correct factory over sights. I had every issue discussed with her last year but after the new tires she has none of the common Commando traits now, no left drift tendency on level path or any road crown slope climbing or dropping. Can let roll down to 20's hands off with only some automatic self correcting fork oscillation that is vital part of what keeps a bike upright on its own. Does not self magnify dramatically as did on old hard tires even at 50 hands off, yIKES!
Does not matter a whit what size wind sail I stick on the forks or sticking out in camping luggage in windy Texas trip, steady as she goes. Prior I've had all these wind catchers and un-equal loads in bags or loose parts to flappy jacket or chains tug my Cdo into hinge zone.


BUTT its still a freaking rubber baby buggy that is un-safe to take chances on.

I Live with THE Hinge each time I hit THE Gravel. I got miles of freeway like paths and often a bit late to get somewhere, so I do not doddle but only takes 40-50's in sweepers for THE Hinge to start. Its my long time drunken friend to tolerate, control or flat avoid. I can ride into it from below by speeding or from above by letting up. I get to explore each facet of THE Hinge onsets and recovery and even better can stay in THE HInge to various degrees of speeds, accelerations and leans. None of this should apply to you all as it took me seasons of knowing I had to crash again so fast I didn't know what went wrong or just quit. Guess what its exactly what happens to all other bikes if pressed over their limits.

This last few outings on Trixie I've taken her into THE Hinge on better than race track sections. Rather faster than the sport guys are willing to do there, though of course not what these moderns can do with good rider. Everything is Factory perfect on Trixie so realtes directly to everyone else's un-tammed Cdo's. All's ya have to do is get over 80's in sweeper leaning 40 degrees or more and keep on the power. Then the counter steering of front to outside and the rear lean pulling to inside - tire conflicts twist frame/iso's up. This starts oscillation when the rear begins to over power the fronts pull outward, forks release some counter steering angle - for two reasons, one tire want to follow the curve direction that rear is dictating & 2nd the rear patch levers through the rear iso pivot to slap the front iso clearance to one side, felt in the fork twitch. If pilot keeps the loads increasing then this can build up by twisting the forks into frame then swing arm and iso rubbers and front mount tabs twist down tubes too, till magnify into full flopping fish off the deck. I practice this on purpose at way slower speed by zig zags in my lane till chassis snap back tends to hop tires off the surface. That scares me so bad imprinted I can't force Trixie into turns my subconscious senses might just do that, but bet I get closer to it on un-tammed Cdo than those w/o THE Hinge launching routine sense. I do zig zags on my SV650, I did it on Ninja 900 and a Harley 88cid cafe- ugh. There is no mystery to me no more on my old drunken friend-foe THE Hinge. So talking handling limits is scary serious and fear is not fun.


Wivel/wobbles occurs in all other motorcycles but one, just the modern or solid mounts raise oscillation freg so delays THE Hinge till it onsets at such hi frequency and force humans can't react fast or furious enough to catch it like you can a Cdo that onsets way more gently slowly - weakly - ugh till full fish flop off deck.

I can slap Trixie's handle bar on one side and she will wobble fork one.5 oscillation w/o bothering the chassis. IF I do a push pull combo on fork jerk the fork wobbles several cycles and onsets the chassis into a weave iike a dog shaking off water. I have sense if I did this in 2 push-pull smacks I'd crash in fish flop off the deck. So I do not risk that. This is exactly what I feel happen on sweepers I've laid into and get a bit lumpy - so I never ever risk THE HInge play into un-known surfaces, EVER! There is narrow zone of recovering or not.
This is exactly what the moderns I've pressed will do too, fork damper or not. Damper just
slight extrends the loads/speed before UN-controlable, witness the TT antic's with best suspension and damper available. They suffer to point they are un-predicable and so kills many a good rider.

I have hit Ms Peel bars so hard it chirped tire but self centered immediately with instant return to neutral in .5 cycle. I push/pull double to cause a snake like wave through chassis but its like a flag in the wind just passes through w/o effect on tires or aim, Really really confident building I tell you, as this is same as striking a fist size rock while leaned and bouncing out a wash board on THE Gravel On Trixie I have to lock body to hold forks in white knuckle grip or stones would trip her right out when going with a bit of spirit. Very wearing and worrying, like hi wire walker, routine skill but any blink of attention or lapse of effort, SPLAT> Peel is much less effort to control, hehe to point i love to jet ski her some, which is not at all like lazy dazy flat trackers wide slides, no sir ree bob. If they'd just turn their front into direction they want to go, boy howdy would they have to hang on like a drag racer on vectored thrust. Any less than that just goes off path at a tangent - ugh.


None of wonder bikes interests me in the least any more, I have no more respect for moderns beyond their bee line power to wt ability. I have had Ms Peel and have not been able to upset her in any way shape or form. So neutral its un-believable so can take on turns w/o any fear of crashing or surprise let goes or slip outs and no bike sensation either but the thrust and sound w/o any athletics but breath and grip holding against the G's draining brain blood to butt.

Those seeking fast handling Cdo often tell me all about THE Hinge limits my friend-F'n foe.
I know how to avoid it going rather fast - do you? Realize the better you get your Cdo to handle the closer to UN-tamed UN recoverable state you can fly into more comfortably.
 
DogT said:
I'm going to disagree here. I've thought about it in my feeble old brain, and I tried this sitting procedure also. I didn't notice any difference in how the headsteady reacts nor how the iso units sit. If you think about it, all you are doing is putting weight on the frame when you sit on the seat, even if you get your feet off the ground and on the pegs. It doesn't change anything with the way the engine still sits with respect to the headsteady nor in the iso's (the frame), it's the same engine weight in the frame whether you have weight on the frame or not.
Dave,
When you have the bike sitting on it's wheels and then add your weight in the seat it does load the iso's/headsteady by pulling the engine/cradle backward. It's because the shocks are not vertical, and the degree that the engine/cradle is pulled backward is a function of how far from vertical the shocks are. The more the shocks are laid down, the more the rearward pull you get for a given load. That rearward force will pull the iso's off center.

DogT said:
What will make a difference is if you jack the engine up with a floor jack and center the isos in their bushings and then tighten the head steady, but I actually think it made it worse on mine. I was trying to reproduce the MKIII spring effect.

You proved that it happens when you did this. Which is exactly what one would get if one sets the headsteady with the bike on it's centerstand, BTW. That is, on a bike that has the centerstand attached to the cradle. I did the same experiment when I was using a PR headsteady. I wanted the iso in the headstedy to carry some load, to function as the MkIII spring would. It was not an improvement.

In the end, it doesn't really matter. The iso's are going to be loaded by the rearward function of the shocks. The only question is whether the headsteady is fighting against the iso's or not. I like the idea that they are not, by setting them up with the loads as they are when you're riding down the road. I don't think anyone could tell the difference if you switched it on them one way or the other when they weren't looking. :)
 
I didn't notice any difference in my head stead mounting whether I'm on or off the bike, that's with the nuts on the rubbers loose. I can see that there may be a slight difference because of the shock compression, and maybe even the front forks. Then I started looking at the MKIII setup with the spring, which I think ludwig has incorporated with his head steady and also some of the other commercially made ones. I came to thinking about this after I put on my Hemmings adjusters without any boots and saw how much the isos were sagging in the mount, especially the front. I sort of reasoned, right or wrong, that it seemed to me that if the iso bolts were centred in the iso mount, it would give the isos more slop to move without starting in an already compressed state, and thus perhaps less vibration. That's what put me on to jacking up the engine and pre-loading the head steady to effect the MKIII spring since I don't have one, although I have some of the parts, I'm working on that and the rose joint there. The effect may have been a bit worse vibration to my sensations. I did try tightening the head steady nuts while I put weight on the bike and that seemed to me of no difference, visually, mechanically or vibratory. I suppose pre-loading the head steady probably put more engine vibration onto the frame there.

My feeling is the best option is the rose joint head steady, and the MKIII spring to center the front isos, I plan on trying that route.

I also note that the rear isos are not centered in their mounts either, but taking the weight of the engine off the isos didn't seem to affect that much at all. My rear ones are actually skewed towards the front. I'm still playing with my iso clearance and right now have the front at 0.015 and the rear at 0.010, and am thinking about releasing the head steady so the weight of the engine again sits on the isos.

Now whether all this affects the tank slap, I don't know, but it's at least worth talking about.

My centre stand is on the frame, so that's a bit different on my bike. Going down the road I don't think it matters a whit.

I guess it all comes down to what works in any individual situation, and that seems to be what we are all striving for. It's nice to hear what works for others and worth giving it a try.

Dave
69S
 
This thread could go on & on but for me it's become clear that tires are key. When I first got this bike it had the typical low speed wobble. After rebuilding both hubs with new bearings & Alloy rims/stainless spokes from Buchanons with a set of new Avon tires, a hiem joit headsteady from Jim Comstock ala Colorado Norton Works, new steering head bearings etc I had no more wobble. BUT as soon as the rear tire started to show a good amount of wear the slow speed wobble slowly started to come back! I'm convinced tire pad has a lot to do with it.
 
gtsun said:
This thread could go on & on but for me it's become clear that tires are key. When I first got this bike it had the typical low speed wobble. After rebuilding both hubs with new bearings & Alloy rims/stainless spokes from Buchanons with a set of new Avon tires, a hiem joit headsteady from Jim Comstock ala Colorado Norton Works, new steering head bearings etc I had no more wobble. BUT as soon as the rear tire started to show a good amount of wear the slow speed wobble slowly started to come back! I'm convinced tire pad has a lot to do with it.

+1

I live I Eureka and ride a section of 101 along the bay. There are mills on the windward side of the road that create a mixture of fierce side winds with intermittent dead air. Riding that road when the winds are up would scare the s**t out of me. I replaced a wornout square cross-section rear tire and it transformed the bike's behavior. Gordon Jennings mentioned this problem somewhere, as does the inscrutable Mr. Fleischer:
Quote
You may be surprised to find out that a well-worn, flatted area rear tire was a HUGE cause for instability.....and high speed scary results are possible. Yes, even in just about a straight line, or very slow curves. This was exactly what Gorden Jennings found out....and I duplicated his testing and TOTALLY AGREE.
 
Hello,
u did not mention if this bike was new to u or u have been riding the bike and this problem developed. In which case would narrow the list of potential gremlins related to your issue. Good rubber goes without saying. If u lost balance weight {s} off the front tire u could have similar symptoms. Just a thought.
Dox
 
gtsun said:
This thread could go on & on but for me it's become clear that tires are key. When I first got this bike it had the typical low speed wobble. After rebuilding both hubs with new bearings & Alloy rims/stainless spokes from Buchanons with a set of new Avon tires, a hiem joit headsteady from Jim Comstock ala Colorado Norton Works, new steering head bearings etc I had no more wobble. BUT as soon as the rear tire started to show a good amount of wear the slow speed wobble slowly started to come back! I'm convinced tire pad has a lot to do with it.

I think that's what I found out when I changed rear tires and the wobble disappeared. I probably mistakenly thought the original tire was defective or was improperly mounted. Although, I can't say I noticed the same wobble when the replacement wore down. All things considered, rear tires can definitely be a contributor to high speed wobble.
 
I too discovered ya can't really tell a thing about handling or isolastic function w/o nice condition tires on both ends AND slightly lower air in the front. I did all last year on old hard tires and couldn't keep up with my buddy Wes on his clapped out '71, with good tires on, nor even have much thrill w/o BAD Scares going into lumpy turns, hardly over the posted speed for the semi's in tights. Really really depressing but a non issue if I just flowed a bit over legal traffic or yellow posted corner warning speeds. The tires act like springs along with the iso rubbers and the chassis tiwist un-twist. Main thing I discovered with a slightly binding Norton headsteady was constant intermittent buzz sense, more on side loads from leans or wind pressure. I did not get the strong engine vibes of too tight iso gaps or something jammed, like mere pebble in between engine and frame as can happen with those using a skid plate. Felt worse than thrown rod which only vibes a cycle or so before dead smooth : ( Did I mention how educational it is to ride some sans top steady to see when and how it comes in to play to keep the severe excitement of THE Hinge at bay.
NOthing noticed till ya forget about it and then swing a bit harder or happen to cross a double paint line just being a bit lazy easy in wide open places, WOWHOO, never ever forget about it the rest of your riding w/o a top steady.

This last month on long down hills I've shut off in N to feel things w/o the engine on top. Also can test in N with engine at various rpm for sense of the iso function w/o the drive train iso loading. My Trixie is now on good tires and smooth as factory can get but not as smooth or secure as fully rod linked set up with essentially factory gaps set. I love my little old Combat and now working up to its fast limits now and then but after full linkage I don't have much respect for un-tamed Commando handling or secure smoothness compared.
There are surprises lurking on just a top link and less so with a front link added, ups the turning loads quite nicely to lull ya - till THE HInge onsets at rather harder rates to recover. With Patton's rear link involved, even by itself - handling security exceeds the top-front link combo, With all 3 I have not for the life of me been able to upset the Cdo or even feel a thing but the urge to go at it even harsher. Then the real advantage of ballarina ice skates shows up over the balloon tires.

Try this test on your Cdo's at 50 above, slap on grip and see what happens, then slap both grips one after the other fast as ya can, [within reason of force ok], then feel what happens.
I've stopped that stuff on my un-linked Cdo as too nerve wracking once tasted a few times.
 
Replaced the rear Avon with one slightly narrower and POOF! PRESTO CHANGO! ABRACASABRA!

my high speed weave went away! :P

Some on here are entilted to say "told ya so."
 
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