Wobble Wobble Wobble

Ok, so last night after finally getting the Mikuni sorted on the '70 (went from 35 primary to a 30), re-adjusted valves to factory specs, reset timing to 28 degrees (was at 19 for whatever reason), adjusted the clutch, checked oil flow, tightened exhaust nuts to within an inch of their lives, etc and took her for a good ride after a satisfying 1 kick start. Wow does she run great now other than being obnoxiously loud because of the open pipes.

I am new to Norton's (but not to bikes after 40 years of owning/riding/breaking/fixing them) and this is the first good ride I have taken on her, so this may sound silly... Maybe not.

First, for whatever reason, the handlebars are not square when riding straight. It does not appear that the bars are bent, but I will take them off and put on a pair of Euro bars that I have as I want them on there anyway. If they're not bent, I guess I will need to check to see that something in the front end isn't tweaked. It has a '73 front end on it with the disk brake, but that shouldn't affect anything. Can you guys think of anything in particular I should check if the bars are not bent?

Second, and more concerning... The bike feels really "loose" above 30 mph or so. There is a distinct wobble in the front and rear ends above 30. It doesn't feel like full-on head shake, but it does feel like it could become that. It is just a very unsettled feeling. Other Commando's that I have ridden did not feel like this. When I got home from the ride, I checked both axles for tightness, checked that the wheels weren't loose in terms of bad wheel bearings, and checked tire pressure again. All good. I guess I could've re-torqued the steering head, and I will when I take the bars off for problem #1 above. Any ideas on anything else to check?

These 2 issues may be related, but I honestly don't know. Again, I am new to Norton's and am just looking for some good advice as to what to check next. I love this bike and really just want to get it right and not make mistake after mistake getting it there.

Thanks again for helping out a nOOb.

Cheers!

Mark

Here are a couple of things I've run into with handlebars you couldn't get straight. I had a '73 T140 Tiger that defied all attempts at using the easy methods to straighten them. Turned out the fork tube on the disk side was slightly tweaked. One way you can check this without tearing the front end down: mark the front of the fork tube with a Sharpie, piece of tape, etc. Loosen the tube in the triple clamp, and rotate it 180 degrees and see if that changes anything. On the Norton, you'll have to break the taper on the top clamp, so at the least, I think you'll have to pull the front wheel.

Another episode was with my current '72 750. It had new tubes, and no amount of adjusting the relationship of the fork tubes with the triple clamps would get the bars on straight. Turned out to be the triple clamps did not appear to have the handlebar mounting points machined straight. They were off just enough, that it made the handlebars always turn to the right slightly. I could try and loosen everything, and try and tweak it to the left, but it never was enough. I thought I was crazy, but a new set of clamps that I scrounged up plainly showed the defect.

As far as wobbles and looseness, don't overlook the quality of the swingarm bushes & spindle, and the rear shocks.

Ah... I did not even think about the swing arm bushes. Great suggestion. I had a similar issue on an old T110 that I had back in the day and that turned out to be a tweaked left fork leg. I will definitely check that. As far as the wobble and unsettledness, could worn isolastics cause it? I sure as hell hope not as I don't know if I'm up to replacing the rears right now.

I was just beginning to think that I have become too spoiled after riding the '08 Thruxton for so long.

Thanks for the suggestions. I take these things to heart.

Check head steady brackets for cracking. Also look for pulled apart or squishy rubbers up there.

Yes I think you probably got spoiled by riding modern machinery.

Yes, worn or damaged (softened) iso's can cause a wobble. The alignment between front and rear wheels will change dynamically with iso problems. On the prototypes we got wobbles when the old style spacer tubes started to flare out at the end under load, but I think they all got service bulletin retrofits and the design was changed after about 100 bikes were built.

This wobble solving has become a sideline hobby to me. Loose warn isolastics will not in and of themselves cause a wobble, But the more warn/loose the more they allow wobble and even magnify it dramatically. Fix them but don't expect to solve wobble fully if the rest of long list of things is not up to snuff. Part of the C'do mystery puzzle worth bragging about when it does work as intended. A crooked fork don't usually bother wobble as bike can crab and run true I've found, but if stem rotation stiff or the forks action restricted there is a magnifying effect of minor road bounce with enough delay in fork or pilot action to give sudden tossing opposite effects that can wobble onset on any lose/warn slacks. Swing arms once bushes renewed should get the spindle stabilizer collars fitted.

Tire condition - even the set of it long stored on side stand are too infamous for wobble onsets. My new restored Combat with mostly un-tweaked frame and top steady is a wobbler now but was not 3 rebuilds prior. I suspect the old K81 front since every thing else is renewed and adjusted close enough shouldn't wobble. No issue just riding hands on bars but better not let go below 50 or give em a tap or dramatic tank slapper I must grab back in under a second. Prior I could slap her
bars and self centered and dampered automatically. MIght try lowering/rising front PSI and see it helps/hurts for an easy clue to follow up on. I will put on newer tire before bothering with the long list reviewed above.

To check swing arm slack also need to grab rim-tire and twist as well
as side to side grabbing near axle level. Eye ball top steady rubbers not in a skewed set. I had one crazy making wobble that turned out to be combo of warn sleeve bushes being tugged by primary chain flop, that tugged on the warn swing arm bushes, only found playing in depression with my chain I felt same rhythm. Taking up some its slack dampened the out of the blue easy cruise wobble till I dealt with real causes. I fear a too tight primary way more than too loose so I creep up on best hot tension after a new rebuilt.

Btw I am uplifted to read your list of thing you did prior - as if they were just checking items off a list, ugh, were it so...

Yeah, I hear you on the list... I did leave out the part where I prayed to the Lord of Lights to offset the potential negative effects of the Prince of Darkness, or the Jester of Boyer for that matter. All that I did was correct the other issues I had noted on my first jaunts about the neighborhood when I first got it prior to actually getting to put some 40 miles on her. The good part is that I am getting great feedback from you guys and not needing to re-invent the wheel, per se, yet. Old bikes over the years have taught me patience in that often when you figure out one problem, you find 2 more. I'll keep you guys posted on my progress if you don't mind.

I had an ignition issue once on my '72 Bultaco that led to random bouts of insanity by the crap called Femsa. PVL saved my life. And we think Lucas stuff is flaky at times...

Again, I humbly thank you all for your input. This certainly makes life more enjoyable.

Mark

Jester of Boyer

Click to expand...

hehe I like that new boyer title. I only know when I've handled much on my C'do's, especially electrics, about half the time I distrubed something that conducts. Can never ever not suspect Boyer's trigger wires, must be upgrade on your terms sooner or its terms later, for certain and erratic starts to running is classic.

Mark the easiest way to test for worn /sloppy swingarm bushes is to put her up on the centerstand, grab the rear wheel at back and move it sideways back n' forth , observing the area. This is why the big guy created winter, to tear apart swingarms n' cradle subframes for the swingarm fix.

Re swingarm...as suggested above, put it on the center stand, grab the rear wheel and move it from side to side. The chain should not go loose and then tight. Modifying the swingarm with some of Windy's Kegler clamps or ala Ludwig is something you should look forward to regardless.

As for the bars not being square to the frame when riding. I have had two experiences. One the triple trees where out of alignment and it took a considerable amount of effort to break them free enough to align the fork tubes. The second I had one tube that was slightly bent, not enough so you would notice until I laid it on a bench and rolled it. At some point, when you have the front end down you should lay them along side each other and roll them on a flat surface.

Russ

As you have been riding and fixing bikes for 40 years I would imagine you have tried backing off the clamp bolts on the yokes, and then trying to move the bars into the straight ahead position, while the wheel is held securely? Very easy for the yokes to become twisted in a minor accident, or even after a rebuild.