Author Topic: CB750K2 Fork Question with Pictures  (Read 1439 times)

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Offline Jamin

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CB750K2 Fork Question with Pictures
« on: June 01, 2009, 06:44:35 PM »
Hi everyone,

My suspension in front seems to be a bit soft, so I changed my fork oil yesterday.  When I removed the cap, I noticed two sets of washers and a bolt on each side sitting atop the spring assembly.  I assume these were placed here intentionally as spacers to avoid purchasing new springs at some point in the past.  I removed them, spun around the block with super-mushy suspension, then put the "spacers" back.  The suspension seems a little sticky at the top both on depression and rebound, even though the seals look good and there are no grooves or damage on posts under the boot.  I'm wondering if the forks need to be aligned.  The steering seems a little wobbly when coasting from 50 mph down to 25 or so, and the suspension travel really dives when applying the front brake.  Since I'm new to the bike and have only ever ridden mine, I'm not sure if this is normal or not.  I've been reading through a bunch of old posts here, and wondering if perhaps I have a slightly bent fork, or perhaps just springs are old and need to be replaced.  I filled the forks with SAE 10W-40 high grade oil and used 7.1 oz in each side.  Now when I dampen the shock, I can hear the oil bubbling and sloshing in the forks.  Never noticed that before, but also never listened for it before changing the oil.   Anyone out there care to take a look at my pictures below and comment on front end alignment?  Is this how it's supposed to look, or is something wrong?  It looks skewed to my eye, and when using the reflectors as a guide, the forks certainly seem to be a bit off.  


The red arrows indicate the misalignment of the reflectors, which to me suggests misalignment of the forks?


Front view


Close up front, perhaps a little lens distortion here, I don't think my wheel is bent


Front view, different angle


Reflectors from the front

I found instructions about fork alignment in another post, quoted below.  I'll go ahead and perform this procedure unless anyone out there has other advice or opinions.  Thanks for the help!

Quote
FORK ALIGNMENT: Slick seals and trick fork oil will get you nothing if the forks are not aligned to prevent binding. The front fender must fit its mounting lugs on the fork leg. Use an adjustable wrench to bend the fender bracket around so that it is a slip fit between the fork legs; the mounting bolts must not have to force the fender out into contact with the threaded lugs cast into the fork legs. Similarly, the fender must slip between the fork legs without having to force it inward. Bend the fender stays so that, like the fender, they neither force outward nor inward on the fork legs. Completely assemble the forks, wheel and fender. Tighten only the bolts in the lower triple clamp and pump the forks vigorously 10 or 12 times. Tighten the top triple clamp bolts. Pump the forks again and torque the axle nuts and fender bolts. This procedure will ensure that the forks are in alignment and will operate as smoothly as possible. It should be performed anytime the fork is disassembled.
« Last Edit: June 01, 2009, 06:51:13 PM by Jamin »
1972 CB750K2

Offline GammaFlat

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Re: CB750K2 Fork Question with Pictures
« Reply #1 on: June 01, 2009, 07:58:10 PM »
The reflectors are not part of or attached to the fork tubes.  The "ears" might be crooked and that shouldn't be much of a problem.  From an "exterior perspective", the forks are pretty much 2 parts: the tubes and the lowers.  The triple tree grabs onto the tubes - you slid your ears over the tubes as they rise through the trees.  To make a long story longer, don't look at your reflectors to assess alignment.  If you disconnected the headlight bolts, I think you'd be able to rotate them (if not too rusty inside). 

I've read (on this forum I think) that the way to test a fork for straightness is to roll the tube on a very very flat surface.  

BTW - really nice looking bike.  

7 ozs seems like a lot - I've heard numbers from 5 to 7 though.  Someone here will know...
« Last Edit: June 01, 2009, 08:19:12 PM by GammaFlat »
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