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Discussion Starter · #1 ·
What causes it?

My '74 CB200 seemed to have a mild case of it when I got it. But, it also had worn tires and stiff steering head bearings. It would get a mild shake as it decelerated down thru 40mph. With both hands on the bars, it was barely there. Slightly worse if only one-handed. Never developed (nor even threatened to) into a tank-slapper.

Meanwhile, I've done a lot of work that I felt SHOULD have eliminated it, but doesn't seem to have. New front and rear tires; rebuilt fork legs with 1/2" spring spacers and new 15-wt fork oil; disassembled, cleaned, regreased and reset steering stem bearings; checked for swingarm bushing play and found no side-to-side play at all that I could detect.

I'm thinking that the steering head is too loose. It was pretty snug when I took it apart (stiff, hardened original grease). It was not as tight when I went back with it, but there was no play that I could detect by moving the fork tubes back and forth.

I've always thought that this was caused by too loose steering bearings, and that too tight bearings led to a kind of weave as the front end was too tight to respond quickly to those microscopic changes one makes to keep balanced as you drive down the road.

The head shake is still there. Just mild as I decel thru ~40mph. Doesn't happen any other time, and only discernible if I have a light grip on the bars.

Thoughts?

Kirk
 

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Tire balance?????

Wheel alignment??? (front/rear in the same plane) Do not trust the chain-alignment marks on the swingarm - they're off on my CB200, by nearly half a mark.......
 

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Discussion Starter · #3 ·
Well, now, out of balance is an interesting idea. I never thought of that.

No, I don't trust the chain alignment marks, either. I measure from swingarm pivot bolt to axle bolt (centerline-to-centerline) on either side, and sanity-check that with rough eyeballing the bottom run of the chain viewed from the rear sprocket looking forwards towards the front sprocket.

The shake is a side-to-side oscillation of the handlebars, like an imminent tank-slapper. This is what made me think about steering bearings, etc. rather than the up-and-down shake I associate with an out-of-balance tire.

That being said, I did not balance these tires at all when I put them on. I meant to have it done, but completely forgot! :oops: :oops:




If that turns out to be it, I wan't a Homer donut! :oops:
 

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Sensei
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Kirk...I'm sure you've already checked all this, but for the benefit of others who may experience a similar symptom/problem...
The 200 has a top bridge that would allow the tubes to project up through, correct? (pinch bolt type) ... Besides the bearings possibly being a smidge loose, please look for different height of legs in trees, OR a slight rotational twist between upper and lower trees, AND/OR a bent or "sprung" lower tree or tube, OR a gap under the top bridge (between it and the stem nut) .... It only takes 0.5 mm of height or alignment between trees difference to cause a sympathetic vibrational harmonic (that apparently shows at 40MPH on your bike)... It is likely also there on accel, but the engine "pull" unloading the forks disguises it.... This is quite common after forks have been completely disassembled.... Set the bike level and plumb, and loosen, adjust and re-tighten in the correct order (ask Bill about the 360 top trees and the importance of doing this in order), all the appropriate clamps/bolts/nuts/pinch points... Should fix it ...
("dented" races or "square" balls can also cause similar effects, but I assume you would have discovered that on cleaning/lubing)
 

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66Sprint said:
Set the bike level and plumb, and loosen, adjust and re-tighten in the correct order (ask Bill about the 360 top trees and the importance of doing this in order), all the appropriate clamps/bolts/nuts/pinch points... Should fix it ...

Absolutely Steve - first the bottom clamp, then the big stem nut(s) on top, then the top triple clamp last.
Probably the number one reason for all the cracked 360 top triple clamps, and why you can't hardly find one anymore.....same on most of these old critters, for the most part...
 

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Discussion Starter · #6 ·
Whew! You guys had me nervous there for a minute. That was the sequence I followed. :)

One thing I did notice that was a bit unusual, at least to me - when I snugged down on the large stem nut, the overall set would get too tight, even though the setting nut underneath did NOT move. I repeated it several times just to be sure. I had never had a bike do that before. So, I had to set it a bit looser than I'd like, and when I snugged up the stem nut on top, the final tightness was correct. I didn't really think about it, and I haven't really thought it thru here. I'm wondering what that symptom means... Something I did wrong? Something wrong mechanically?

Hmm.....
 

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Sensei
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Kirk... the stem "tightness" should not change when you tighten the top nut....only when you adjust the "setting nut"... Is it possible that some of the stem's threads are worn or stripped?.....(or cross threaded?)
 
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