Front Axle query

[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]

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 🤞

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.

[Andrew-S]

.......PS - Andrew! You’re Avator looks spookily like mine! You been raiding my photo files? 😂

Hi Simon,
They do look similar, but I guess there's only so many ways you can take a great photo of a CB750 - if I had been on a covert photo raid wouldn't it have looked like this.....  Edit: I think you need to click on the image to get the effect I was after?   

[SeanFD]

Ah! You were trying to take a covert pic of yourself! 

K2: I have roller bearings in the head. Would the same happen with those?

Thing is, the bike was running perfectly; I’d just completed a 5,000km ride with no issues. Then I changed the shocks and springs, didn’t have a chance to do a test run before heading off on the 2nd leg, and experienced the wobble 200m from home. I went a bit further to see what would happen and once speed increased, the wobble disappeared as quickly as it had appeared. So I went on and lived with it for a further 20,000km.

I took it for a short spin yesterday having replaced the seals, cleaned and rebuilt the forks. The wobble seems to have gone, although previously it was only really bad when the bike was fully loaded. The fact that the tyre pressures were less than 20 psi – the bike has been sitting for a while – didn’t help with the assessment. I’ll be trying again once the rain stops.