SOHC.co.uk Forums > CB750

Front Axle query

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Skoti:
Hello Lobo,

thought you should see this Honda service bulletin, just incase your K2 has been fitted with an earlier K1 wheel at some point.

http://info.sohc.co.uk/download/cb750-service-bulletin-26-23-12-70-front-brake-disc-mounting-bolts/


I was also thinking that if you pull in the fork sliders like you described then tighten up the axle clamps you may increase the friction on the fork operation.

Somebody else may correct me, but it's probably better to compress the forks a few times with the bike off the main stand before fully tightening the axle clamps. 
That would ensure the stanchions and sliders are perfectly aligned.

Is that making sense? 

Good luck

Skoti

Lobo:
...thanks Skoti, your friction concern did indeed cross my mind. Tbh, the minimal ‘force’ (if that indeed is the correct word) it needed to gain 1mm was here-nor-there I reckon, especially when you go on to consider the same, but massive forces, under braking.

Alas I can’t open your bulletin... perhaps coz I’m on an iPad.

Many thanks,
Simon

SteveD CB500K0:
That’s something I’d not noticed before.

iOS is a real bugger sometimes. Apple refuse to open pdf files without using the Acrobat app. PC browsers will open them in a new tab.


Sent from my iPhone using Tapatalk

K2-K6:

--- Quote from: SeanFD on September 27, 2020, 09:22:36 AM ---
I’d be interested to hear what others think of this, because after replacing the springs and shocks (IKON also) the bike developed a severe head-shake at about 35-35kph if I took one hand off the bars. This quickly settled and at higher speeds it was fine. I have yet, 20,000km later, to solve this problem, so any ideas welcome. I have just rebuilt the forks completely while replacing the seals, so here’s hoping 🤞

--- End quote ---

Have you verified that the headstock bearings are absolutely smooth with no notching very close to centre?

If you've got a notch that essentially pulls the steering very slightly off centre/dead ahead, the wheel will want to turn the bike slightly with the geometry castor/trail etc trying to neutralise by centering it,  which will produce an oscillation as the two essentially argue it out. As you increase speed the wheel gets significantly more gyro effect and overcomes the above.

It can be almost undetectable as if you lift the front to rotate the forks it doesnt sit on the bottom race,  so hard to feel. More likely on a "turning plate" type of device so you can feel more sensitively with that bottom race loaded with bike's weight.

K2-K6:
Also any tire runout,  both front and rear can set off a "shimmy" at low speed that doesn't develop further as wheel speed and  gyro forces rise which then takes  precedence in keeping it straight.

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