Fork/wheel/brake caliper/yoke alignment - HELP!

[Shrubnuts]

Hi all.

Firstly, my name is Steve and I'm new to Forums and new to CB400SF's. I'm a car gearbox mechanic by trade though so have a fair amount of mechanical knowledge, engineering aptitude and access to a well equipped workshop and engineering firm.

I have started work on my wifes 1998 CB400 Super four to get it through an MOT and ready for when she passes her test. The first job is to sort out the leaking fork seals. Simple enough task but I've hit a few curious issues. When I loosened off the front wheel spindle and pinch bolts I noticed two things immediately. Firstly, the holes in the end of the spindle that are used to put a suitable lever through to rotate the spindle were slightly recessed into the bottom of the fork leg. I'm pretty sure they are supposed to be exposed for access. The second thing was that I'm pretty sure the fork legs had around 3mm of inward flex to actually touch the wheel spacer and speedo drive. The next thing that seems wrong is that the left side brake caliper had two washers per bolt between the caliper mounting lugs and the fork legs to space the caliper towards the wheel. The right hand caliper had none. I don't think either side should be spaced? I looked more closely and it seems that the caliper pistons on the right hand side (un-spaced caliper) were evenly protruding the caliper, whereas the pistons on the outer side of the caliper on the laft side protrude significantly further than the pistons on the inside of the caliper. It seems to me that an attempt has been made to move the left side caliper closer to the disc but it is still too far away. The only explanation I can come up with is that the yokes have been changed at some point and ones with the fork centres further away have been fitted, but the clocks seem to mount perfectly to the yokes. I somehow need to find someone with a known good bike who can measure the centres of the tops of the forks and tell me how far apart they are. Is there anybody out there who could do that for me please or who has any ideas what else could be wrong?? This model runs Brembo front calipers if that makes any difference?

Thanks, Steve.

[amorti]

Hello mate,

Apparently (according to google) there was indeed a limited edition run of 1997 bikes with Brembo brakes fitted. I never saw nor heard of it before! So either Brembo made some calipers with suitable bolt spacing (they did so also for a limited edition Yamaha XJR400 so it's possible) or Honda fitted different fork lowers with different bolt spacing. If it's special calipers then look after them as you will never see another set again and would have to go for regular calipers if they died - not a big deal but it loses the specialness of your bike. Tell us the distance between the bolt centres and we can tell you either way.

If you are using the original front wheel and discs, then the right-hand wheel spacer should be some 3 or 5mm longer than the left-hand. Is it possible someone has mixed them up, or replaced a lost long one with a short one?

Bent forks is an MoT fail not to mention will cause the forks to have excess friction and will over stress the fork seals too. You can test if the forks are bent by taking them out the bike and rolling them on a flat table. They usually bend where they sit in the bottom yoke, so you can't always "see" the bend without removing the fork from the bike. Be careful not to mark the chrome while doing this. Honda forks are mostly a parts-bin jobbies, so the internals will 99% likely be the same as any other 400SF even if the bottoms are different. Fork stanchions can be replaced from www.allbikeengineering.co.uk . You should also change the bushes if the forks have been used bent as they will likely be worn out, come back to us for more info if that's the case. It is not really worth having them straightened unless it is only a very very minor bend.

show us some pictures?

[Shrubnuts]

Hi.

Thanks for getting back to me. The spacer on the left side of the wheel appears to be the speedo drive. If that is the case then they can only go one way round. Are there any spacers on that side in addition to the speedo drive? The other thing that I thought about is if the wheel has been changed to maybe an earlier model that is narrower across the hub? That would explain why the calipers don't line up with the discs. How do I post pictures on the forum? Can I post them in a message? I'm going to put the forks back in this week and have a good measure up. The forks seem very straight and odly enough there doesn't appear to be any play in the fork bushes. I'm going to fit the new seals and see how I get on

[amorti]

Hi.

Thanks for getting back to me. The spacer on the left side of the wheel appears to be the speedo drive. If that is the case then they can only go one way round. Are there any spacers on that side in addition to the speedo drive? The other thing that I thought about is if the wheel has been changed to maybe an earlier model that is narrower across the hub? That would explain why the calipers don't line up with the discs. How do I post pictures on the forum? Can I post them in a message? I'm going to put the forks back in this week and have a good measure up. The forks seem very straight and odly enough there doesn't appear to be any play in the fork bushes. I'm going to fit the new seals and see how I get on

I am pleased for you that the forks are straight, as it's a PITA if they're not. Screwed up my original diagnosis, though! Sometimes fork seals "just fail" - if there had to be a cause of death named, then it's often because the bike has sat laid up for a while, and the seals dry out and crack. It sounds like a puzzler for sure. The problem for me / us with diagnosis is that your Brembo SE is seriously rare in the UK, so I doubt anyone on here will have seen one to know if there should be any differences or not.

Best bet for posting pictures is to host them on a free site like photobucket, and link the picture here. Host the pictures in as big a resolution as you can, and put weblinks instead of IMG tags as this forum won't let you use big pictures otherwise.

Next thing is just taking careful measurements. Fit the forks back in without the wheel and check the width between disc "slots", then measure the distance between the discs on the wheel and see if it is the same. If that matches, then it points to the RHS spacer since as you say the speedo drive either fits or doesn't fit, and if it's wrong then the speedo won't work. ps, be careful lining up the drive tabs on the speedo.

Also offer the axle in without the wheel in the way, and check that it's correct. Usually those two little holes should protrude clear from the fork leg, but only just. The axle stops itself on the step inside the axle hole. Again though, no idea if your SE is different.

[Shrubnuts]

Hi again.

Ok, tonight I stripped the forks down and had a better look at them. Turns out they're bent! Very bent!! Sorry to have wasted your time with the wrong info. I'm guessing the solution is to try to find another set of forks. Maybe Ebay or the forum can get me out of trouble. I don't know how successful straightening the originals is likely to be or how much a service like that would cost. I guess the chrome would suffer from being brittle as well?? Any ideas greatly appreciated.

Thanks, Steve.

[amorti]

Hi again.

Ok, tonight I stripped the forks down and had a better look at them. Turns out they're bent! Very bent!! Sorry to have wasted your time with the wrong info. I'm guessing the solution is to try to find another set of forks. Maybe Ebay or the forum can get me out of trouble. I don't know how successful straightening the originals is likely to be or how much a service like that would cost. I guess the chrome would suffer from being brittle as well?? Any ideas greatly appreciated.

Thanks, Steve.

You will struggle to straighten them, yes. For the reasons you state, plus the fact that they rarely bend in a nice arc but usually against the yoke so you end up with a crease if you try to straighten them.

Show us a picture? Because yours is SE, you will never again see a complete set of forks from that exact model. Your main hope is that the internals are identical to a more common-or-garden 400SF. If they are then the forks are also identical to many many hondas, and your search gets easier. e.g. CBR600F2, which are same but 7mm longer according to here:
http://www.allbikeengineering.co.uk/htm ... 110301.pdf
so you could just leave that through the yoke.

Your best bet if the money is available is to buy new fork tubes off ABE, brand new chrome so you know there's no pitting and seals will last you.

[Shrubnuts]

Hi.

Thanks again for all your help. I gave in and bought 2 new stanchions from ABE. Thanks for the tip. Hopefully it'll all be ready for MOT by the end of next week. I figured it's probably worth the expense not to have forks of unknown origin turn up!!

Cheers, Steve.

[amorti]

Hi.

Thanks again for all your help. I gave in and bought 2 new stanchions from ABE. Thanks for the tip. Hopefully it'll all be ready for MOT by the end of next week. I figured it's probably worth the expense not to have forks of unknown origin turn up!!

Cheers, Steve.

S'all part of the service
Good call on new parts. Forks are problematic as you never know if they are straight, seals are leaky, chrome pitted etc. I just hope they fit and that yours doesn't have different internals but tbh, it is unlikely you'll have an issue.