82 CB 750K Fork Questions

classic Classic list List threaded Threaded
15 messages Options
Reply | Threaded
Open this post in threaded view
|

82 CB 750K Fork Questions

acquinn91
Hey guys,

For the past year or so I ahve been struggling with my forks on my 82 750K. Since building it last april, I have replaced fork seals 3 times and still am leaking. This model runs air assist forks which I am frankly not a fan of. The FSM is not very helpful in the addendum when it comes to this model.  It says to take it to a dealer, and I am assuming this refers to servicing the air bushings.

The fork does not hold air pressure, and after fussing with the system, I transitioned to progressive springs and no longer run air. The forks still leak after seal changes. There are no gouges or scratches in the tubes that could cause the leak. One post I have read suggested filling the tubes from the bottom with a vacuum. I have always filled from the top. Could this be part of my issue?

Any advice here is appreciated.

Furthermore, moving forward I am considering going with a different fork entirely. I have read that some of the VFR forks are 37mm as well. I am wondering what Axles these run and if my CB wheel will bolt up. Also, do SOHC CB's run the same size axle, so I could conver to dual disk?

Thanks guys
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

TOOLS1
Administrator
Top or bottom, filling would make no difference in whether it leaks or not. Are you damaging the seals while installing them? These are tricky to install on that model fork. Also, are you installing the seal right side up? Some times it is hard to tell which side goes which way.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

acquinn91
Thanks TOOLS,

For lack of a better way to say, i am placing the side of the seal with the wavy inner diameter down. If that has been the problem this whole time I am  going to feel like the biggest numbskull.  Furthermore I am using two old seals stacked on top and a pvc pip over the fork tube. Then using a rubber mallet to tap the seal into place.
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

TOOLS1
Administrator
"Wavy side down"? The side that you can see the little spring in goes down.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

shinyribs
Administrator
TOOLS1 wrote
"Wavy side down"? The side that you can see the little spring in goes down.
TOOLS
This. ^^^

Also, by chance, are you using "Leakfree" brand fork seals? They're terrible TBH. I've seen two sets of these installed and both sets leaked instantly.
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

Re-run
Administrator
In reply to this post by acquinn91
Another thing that happens is after people put in new seals, they nick them putting the slides back in. Lubing the slide and seal first, kinda like putting oil on an oil filter oring, helps things slide together better and not scratch, cut, or nick things.
The ride IS the adventure. The destination is just to get gas!
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

acquinn91
In reply to this post by TOOLS1
Hey sorry for the delay in my response. I have been using K&S fork seals. There are springs on the ID for both sides of the seal. One side has a deeper recess, and I have been placing that down. This leaves the side with a flatter face on top. Is this correct?
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

TOOLS1
Administrator
That should be correct. I use the seals that Cycle-X sells, but I do not know what brand they are. However I have never had a problem with them.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

acquinn91
So I did another set of K&S seals. Thought that maybe I had the orientation backwards and inverted them, no such luck. Just like previously, they are leaking immediately. I am using a properly sized pvc pipe as a driver, striking two old seals stacked on top. I prelubed the new seal. Kind of at a loss at this point.

I just ordered seals from a different brand, and I will give this a try.

Any advice on a fork swap? I would like to keep a spoked front wheel, but if I swapped I would be interested in a dual disc setup. Thanks again for any help
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

Re-run
Administrator
It could be possible that the seals are not quite the correct size. At this point, you have tried the same brand a bunch of times. Maybe now is the time to find a different brand.
The ride IS the adventure. The destination is just to get gas!
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

LukeM
Administrator
I am running into a similar situation with my '84 Shadow.  I suspect a previous owner dropped the bike somewhat gently on the left side.  This may have distorted the lower fork slider.  When I swapped the seals (with genuine Honda parts) 2 years ago, it ran fine for a while, and then started weeping from the left side.

The right side went in just as smooth as silk, but the left side needed a LOT of persuasion.  I was very careful not to whack the seals too hard.  I also used a piece of PVC to drive them home.

I found a used pair of forks on EBay for about $50 or so, and I'm swapping the seals as a precaution. Just need to find some spare time on a weekend.

Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

Re-run
Administrator
I wondered about that. It is possible the bike's PO ran into something and bent the forks a bit. I guess the next time the forks are apart, set a straight edge against them and see if they are straight. I would also check to make sure they are completely round, you never know, they could be ovalish.
The ride IS the adventure. The destination is just to get gas!
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

acquinn91
Nothing is visibly bent or out of round but i will inspect further next time I have them down. There was no visible damage before the bike was broken down, and I rebuilt it from a basket case last year. Updates will come
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

Re-run
Administrator
Well, forks are pretty simple things really. You have 3 main causes of problems: Damage to the forks or seals. Incorrect seal size. Incorrect installment. There isn't much else you need to worry about.

No one has reported incorrect sizing, but I mention it because some here have had brake pads the wrong size and so I put it out there as a possibility.

Only other thing I could suggest would be to take pics as you re putting in the seals. It is easy for a person to not mention something if they think it is inconsequential, that may be very important. If anything, we could help you rule out incorrect installation. leaving only 2 remaining possibilities.

The ride IS the adventure. The destination is just to get gas!
Reply | Threaded
Open this post in threaded view
|

Re: 82 CB 750K Fork Questions

acquinn91
Hi Guys,

Just to follow this up, I switched brands to BikeMaster from K&S. They popped in much easier and I have had no leaks to date. Maybe the OD is slightly different.

Cheers