SOHC.co.uk Forums > CB350/400

Front forks /wobbly steering

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ricardo:
Hello everyone.
I've removed my front wheel to investigate. Pads are good. bearings seem to be ok but how can I be sure? I noticed that with the wheel off the forks will rotate independent of each other . Is that correct. I always imagined that they would stay in the alignment they are in when the wheel is in place.

Ricardo

K2-K6:
The bottom of the fork legs are effectively "floating" with no rotational location,  that's correct.

They are only aligned by clamping the wheel spindle when correctly assembled and tightened. So all ok if clamps and threads are in good order.

The front mudguard is considered as brace to help,  but if it has rubber mounts it can't really contribute much.

Initially you've not flagged anything untoward there.

ricardo:
Many thanks
Ricardo

TrickyMicky:
Whilst you have the front wheel removed, it's nice and easy to check if it is out of balance. Hold/support the wheel spindle, and just give the wheel a gentle spin, when it stops, make a chalk mark at the 6 o'clock position. Repeat this a few times, if it stops at the same place each time, then your chalk mark is the heavy spot and a balance weight should be affixed diametrically opposite, correct weight determined by trial and error I'm afraid! When giving the wheel its slow spin, if the wheel bearings are in good order, you should not be able to detect any noises or feel any harshness when holding the axle. As you have the front wheel removed I assume the front of the bike is supported leaving the forks free to  move, Slowly move the handlebars from lock to lock, there should be no resistance or roughness throughout the travel, especially at the straight ahead position. Lastly, once again as the front end is free to move, ensure the bike is secure, then grasp the bottom of the fork legs and push and pull them in the fore and aft direction, if your steering head bearings are good there will be no movement at all.
   Eons ago, when I had a CB750, it had a front wheel which was only very slightly out of balance. Did not take any notice until one day when going on holiday, two up with a very heavily loaded rear carrier, i closed the throttle at about 40MPH and took my hands off the bars to adjust my goggles, HOLY SHIT! It went into the biggest tank-slapper I've ever had. Please take those few extra minutes to check those few items. Happy riding, and stay upright. Michael.

K2-K6:
The point Micheal made about checking the smooth turning of fork yokes has particular significance in this problem. Absolutely any roughness however small can cause error.

The original headstock bearings are ball and race type.  If there is an indentation just very slightly off true straight ahead geometry (you'd feel this in checking) then it can cause the front forks to "sit " in that alignment,  which would turn the bike in one direction slightly.  The natural steering geometry will "try" to make the bike go straight down the road with no input to the bars.  The conflict between the two can make the forks oscillate in and out of that bearing dip,  making the steering wobble. Even adjusting the chain and getting a slight bias on rear wheel alignment can bring this in or out of play.

The headstock bearings are ideally replaced for taper roller bearings which ordinarily resist deterioration under use much more effectively.

Something else to look for in detail,  the wheel spindle clamps look universal but are directional.  There's an arrow cast into them that should point forward in direction of travel,  they would be clamped first by the leading stud to get them seated metal to metal ( that part of the casting in longer to facilitate) and only then the rear stud tightened to finally pinch the spindle.  It's a subtle design,  but often missed.

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