Author Topic: CB400 Forks  (Read 1115 times)

Offline 2 for the soul

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CB400 Forks
« on: June 28, 2020, 09:00:05 PM »
Hi,

First I'm going to apologise, I found a thread some time back that ended around 2018/19 and was hoping to resurrect the conversation as my issue is of a similar ilk but I've spent a good hour trying to find it and had to give up!

I put the front wheel back of my '76 CB400 onto the spindle, arranged all the parts and low and behold there was about 1/4 inch gap between the left fork leg and the speedo drive (see picture 1). The front fender and brake ass. all fit to the right although the calliper is ridiculously close to the spokes (see picture 2). Not sure if this is right?

The chap in the previous thread eventually decided to clamp the forks together from the other side, much to everyone else's dismay for obvious safety concerns! I've twisted the forks in the yokes and the spindle end didn't appear to move any closer to the drive, I've taken the forks off and tried rolling them along a surface with a light behind and there was no discernible bend, I've loosened them in the yokes and pumped the front down to try to settle the alignment etc etc. The only slight hint of a bend I could see was by holding both stanchions together and whilst they were touching at one end, at the other there was no more than a millimetre between them - no idea if this could cause 1/4 inch movement at the spindle but it seems unlikely?

There are, however, scratches to the surface of the stanchions at the end nearest the spindle (see picture 3 and 4) indicating they're rubbing against something, does anyone know if these scratches would indicate a bend in one or both forks?

I can obviously get new stanchions but they're pretty costly and I'd rather not only to find they're not the problem so I now come to my main questions:

Is there another 'del boy' style garage technique I can use to see if my stanchions are bent? Or a way to see if the lower part of the fork is the issue?

Does any one know of a similar style of front end that would be a direct replacement? Ideally one that I could continue to use my wheel and hub with so just the forks and TT and ideally something I don't need to sell a kidney for.

Thanks very much in advance for anyone's help, and again very sorry if I'm missing a thread of the same topic!

Offline Bryanj

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Re: CB400 Forks
« Reply #1 on: June 28, 2020, 09:30:49 PM »
Starting from speedo drive side spindle goes through drive, wheel bearing, internal spacer, wheel bearing, external spacer into nut with hexagon next to spacer.
Are all those there and the bearing retainer screwed all the way in?

Offline TrickyMicky

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Re: CB400 Forks
« Reply #2 on: June 29, 2020, 08:04:19 AM »
Looking at your pics, it gives the impression that you are trying to instal wheel/forks with the bike on centre stand and resting on the front wheel, makes it bloody difficult, have only recently installed newly rebuilt wheel with wood blocks under engine and rear end strapped down. The photo showing the front disc gives the impression that the wheel is canted over.
     Are both the forks installed at EXACTLY the same height in the top yokes?
     Looking at the scuff marks, have you possible had the legs re-chromed/re-ground? (Correct size?)
    Have you got all the spacers/collars attached in the correct place as per attached diagram?

Offline andut

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Re: CB400 Forks
« Reply #3 on: June 29, 2020, 09:59:43 AM »
Check you have the brake side spacer fitted (item #154 in the parts illustration above) - I recall that the spacer is longer than the 1/4" you're looking for, but it does recess into the brg to give about that offset.

Offline 2 for the soul

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Re: CB400 Forks
« Reply #4 on: June 29, 2020, 11:59:41 AM »
Hi everyone,

Thanks so much for the speedy responses!

So I've got some blocks under the engine and the rear wheel strapped down so i can attach/detach the wheel as often as I like. Once it's in place i've been putting a block underneath to keep it firmly against the forks until I get the spindle clamps on. I've got the straps on the lower yoke and one's tighter than the other which is probably why it looks wonky. Both forks are clamped in at the top the same, and I don't think they've been re-chromed, I polished them up when I got the bike but only the space above the dust cap.

I've definitely got all the pieces from the diagram and in order, I've used the one from the Haynes manual, the one from the Aladdin's cave copy of the manual and one from CMSNL (they're all the same) and i've definitely got the pieces. The bearing retainer appears to be screwed in all the way and is flush with the surrounding hub.

I've definitely got the brake side spacer which sits into the bearing a bit, I've measured it and it's 17mm - so not sure if this is too short or the wrong spacer??

Thank you so much guys!


Offline TrickyMicky

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Re: CB400 Forks
« Reply #5 on: June 29, 2020, 07:53:20 PM »
Y'know, I think that at this point, whilst you've still got the benefit of a hydraulic lift, drop the wheel out again, slightly loosen the clamps on the yokes just enough so that you can turn the forks if needed, Fit the mudguard, you will need to do this anyway before the wheel is fitted as you cannot get the bolts into the brace part of the 'guard with the wheel in. By having the yoke clamps eased off slightly, the tightening of the mudguard brace bolts will ensure the forks are level and facing in the same direction. Fitting the mudguard stays even helps a bit more.
    Make sure that the brake caliper swings nice and freely on its pivot so that it goes where the wheel and disc want it to, and fully back off the small adjuster bolt with spring to give you lots of wiggle room for the disc when re-fitting the wheel.
    Before fitting the wheel, have a slow final check on the location and fitting of all the spacers etc.  I have just been out to look at mine, and looking inside the nut on the left side of the axle, there are just about two threads showing, and all is nice and tight.
  Looking at your pics, the wheel is too far over to the left side of the bike, so by doing all the above, hopefully everything has got just enough looseness in it to let the wheel adopt its correct position.
    If its of any consolation, I've jusy checked on the caliper to spokes clearance, and with the wheel set up correctly, with my tiny hands I still cannot get my little finger between back of caliper and spokes! Once it's all bolted up it ain't gonna move!
       Regarding the scuff marks on the bottoms of the fork stanchions, try and imagine when you are riding along on anything other than a billiard table, when the front wheel hits a ridge or pothole not all of the shock loading is upwards, some of it is in the horizontal lane of front to back, so if the forks are still working ok and there are no leaks, I would just accept it as normal wear and tear. If you aew old enough to remember the Ariel Arrow, they were fitted with trailing link suspension on the front forks, so when you hit a bump, the wheel moved backwards and upwards. It worked, it's a know problem, one day when you're bored, stude the suspension on the trailers of the trucks which carry plate glass, brilliant. Must go, the wine glass needs replenishing. Be lucky

Offline ka-ja

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Re: CB400 Forks
« Reply #6 on: June 30, 2020, 09:44:30 AM »
Ariel Arrow was my first bike! very fond memories.
nice bike,nothing in the bank

Offline 2 for the soul

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Re: CB400 Forks
« Reply #7 on: July 02, 2020, 07:46:12 AM »
Hi everyone,

Thank you so much for this, I got the forks loosened and couldn't actually get the mudguard to attach to both sides at once, not even pulling the forks together.

However, I think I have found my problem. Basically I pulled the forks down so they were at normal position and measured the distance between them at the top yoke and at the bottom of the stanchion - big difference with the bottom being wider as expected. I then pulled them through until they were only going through the top yoke. Although they weren't necessarily straight front to back, the distance between them was within 0.25mm. I then pulled them back through so they were only held by the lower yoke and they were back to being about 5mm out. So I think the lower clamps on the triple tree are somehow bent slightly out from each other, whilst the upper yoke appears to be fine.

Plenty of replacements on eBay for CB400N or other model types, does anyone know which, if any, other Honda CB triple trees are a direct replacement? I found a very nice billet alluminium one on DimeCity, but it's nearly $750 all in (so around £600) which is a lot if it turns out it doesn't fit.

Any way, hopefully once I can find a replacement triple tree the problem will be sorted and I'm hoping the guy who had this problem originally can see this thread and can try the same to see if that fixes their problem too!

Unfortunately not old enough to remember the Arrow but looked at pictures and looks like a damn good idea!

Thanks again for all the help everyone! :D

Offline Deano400

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Re: CB400 Forks
« Reply #8 on: July 02, 2020, 08:46:50 AM »

Offline TrickyMicky

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Re: CB400 Forks
« Reply #9 on: July 02, 2020, 09:37:47 AM »
Before you rush off spending hard earned dosh, the top and bottom yokes are fairly substantial castings and don't bend too easily. I've seen crash jobs where the forks have looked like a pair of bananas, but the yokes have held out ok. If the yokes were even slightly out of true I don't think that you would be able to slide both of the fork tubes through them, they are highly precisioned pieces of steel. If it's any comfort, the fitting of the front mudguard, in my opinion, has always been an absolute s--t job!

Offline 2 for the soul

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Re: CB400 Forks
« Reply #10 on: July 05, 2020, 01:12:39 PM »
Thanks for the feedback, and actually it does make sense that they're solid as they're so thick! Can't get my head round how the forks would  be straight through one yoke but not the other, and yet the forks do go through both (but end up squiffy at the bottom!). I've ordered a CNC ally triple tree as it was something I was looking to do further down the road so it's not a total waste of cash. I'll see how the forks fit in the new one and go from there.

I wonder if I messed up the alignment when I changed the ball bearings to a roller bearing kit? Is that even possible? Not sure how that would affect the forks left-to-right alignment  ???

Worst case scenario I can order another set of forks (I just won't tell the missus) but if it's not the yokes or the forks I'm not sure where else on the bike the problem could be coming from!

Again, thanks for all the great advice and feedback, and the website looks great Deano :) thanks

 

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