Topic: Bouncy Forks, 74 cb550

[pirate4pleasure]

Hello again guys, Sorry to sound like a newb but I just like to check with the pros before i get into wasting time and money on my project bike.

So I just got my ride running after screwing around with electrical issues for the past week and wanted to know about Forks, I am new to older bikes and noticed my front forks are bouncy. really bouncy. So im assuming it would be the fork seals as Im sure they have never been changed. Is there other things to be checking or is it just good practice to rebuild older forks?

Here she is:

[Toxic]

Yes, it is a good idea to rebuild your forks.  It looks like you have done allot of work on the bike so why not do the forks.
The seal won't make it bounce.  If they are shot you will notice fork oil on the upper tubes.
Your issue is probably a fork oil issue.  Not enough or the wrong type.

It is an easy project.  Your manual will give  you specs on type and volume.

Nice bike but why does it look so jacked up in the rear?  How much longer are the rear shocks over the stockers?
What is the deal with the front tire?  It looks like a slick.
also what is the silver cable showing under the rear brake stay?

Got more pic?  Would love to see more of your ride

[MCRider]

With the rear up, you have decreased the rake of the fork. The "angle of deflection" is now so steep, that hitting a bump simply caused the whole front end to go up, and then down, without pushing the lower leg into up its range on the tube. Maybe.

I'm no expert, and certainly your fork needs to be gone thru completely, a thorough flushing and the right weight of fresh oil, and non-sacked springs, but i think you'll still have to restore some rake to get it to feel right.

OCICBW

Looks nice though.

[pirate4pleasure]

Yes, it is a good idea to rebuild your forks.  It looks like you have done allot of work on the bike so why not do the forks.
The seal won't make it bounce.  If they are shot you will notice fork oil on the upper tubes.
Your issue is probably a fork oil issue.  Not enough or the wrong type.

It is an easy project.  Your manual will give  you specs on type and volume.

Nice bike but why does it look so jacked up in the rear?  How much longer are the rear shocks over the stockers?
What is the deal with the front tire?  It looks like a slick.
also what is the silver cable showing under the rear brake stay?

Got more pic?  Would love to see more of your ride

Front tire, is normal, just looks off because of the rain and picture etc. the shock are just a couple inches higher with the mounting location changed. I was going for a much more aggressive Cafe racer style. I also added rear sets and a modified frame obviously.

[pirate4pleasure]

here are some more

[dave500]

the seals wont really affect the bounciness,unless they leak badly,how much oil of what sort is in them?

[pirate4pleasure]

I havent check yet, Im going to drain them tonight and fill them back up. the manual says premium ATF fluid? once I fill them back up Ill have a better idea of the fork seals although I think I would like to take them apart to check everything out.

[dave500]

dismantling them will give you more satisfaction aswell,,youve gone this far on the bike,and saftey and handling is where its at.

[pirate4pleasure]

you bet, I love ripping things apart and I will feel much more comfortable knowing I have ripped it apart myself.

[pirate4pleasure]

So It looks like the forks just have water in them  im guessing the only way that could happen is if the seals are gone. easy fix


is there anything else that could have caused that?

[Retro Rocket]

Just adding to something MCRider said, by jacking up the rear you have changed the rake at the front making it steeper and reducing trail, that will make the front steer quicker, i would add a steering damper to avoid head shakes {tank slappers}..

[Retro Rocket]

Just adding to something MCRider said, by jacking up the rear you have changed the rake at the front making it steeper and reducing trail, that will make the front steer quicker, i would add a steering damper to avoid head shakes {tank slappers}..

And a fork brace...

Yep, i didn't look at that but a front brace will help also.

[pirate4pleasure]

Just adding to something MCRider said, by jacking up the rear you have changed the rake at the front making it steeper and reducing trail, that will make the front steer quicker, i would add a steering damper to avoid head shakes {tank slappers}..

And a fork brace...

Yep, i didn't look at that but a front brace will help also.

 will do, thanks guys

[thrutheframe]

What did you wrap your exhaust with?  Moving the shock mount locations back to the original position would definitely help with the front end bounce. 

[Retro Rocket]

What did you wrap your exhaust with?  Moving the shock mount locations back to the original position would definitely help with the front end bounce.

Not necessarily, lots of racers do exactly that, new seals and oil will go a long way to fixing the problem> 

[TS250]

Off topic, but there's no way your chain isn't grinding away on your swing arm at the pivot.  Are you running some sort of chain guide/tensioner/roller/etc?  You need to address that. 

You're going to have to run your chain pretty loose with your swing arm at that extreme angle.

[LesterPiglet]

also what is the silver cable showing under the rear brake stay?

Bent rear brake rod.

[pirate4pleasure]

What did you wrap your exhaust with?  Moving the shock mount locations back to the original position would definitely help with the front end bounce.

Not necessarily, lots of racers do exactly that, new seals and oil will go a long way to fixing the problem>

I have yet to even ride it. I drained the oil last night and it was only a couple ounces of water so my guess is thats the key. plus shot seals

[pirate4pleasure]

Off topic, but there's no way your chain isn't grinding away on your swing arm at the pivot.  Are you running some sort of chain guide/tensioner/roller/etc?  You need to address that. 

You're going to have to run your chain pretty loose with your swing arm at that extreme angle.

No I have clearance actually. I was looking at exactly that when I was designing it. I will also make a runner to be safe tho.

[pirate4pleasure]

also what is the silver cable showing under the rear brake stay?

Bent rear brake rod.

you got it, Fixxed now! those pics were taken during transport.

[somesuch]

If the gators on the forks are stiff, they will contribute (in addition to water )to a bouncy front end feel......if they are very old and very stiff, they will contribute greatly. I had a bike where cutting off the gators made a huge difference in how plush the front end felt.

Just an aside, last night I rode my bike for the first time a meaningful distance on a winding road with my Tkat fork brace, and I must say the difference is obvious, and the improvement is worth while.  Also, as already mentioned, look into the steering damper because of your steeper rake, and decreased trail.

[TS250]

No I have clearance actually. I was looking at exactly that when I was designing it. I will also make a runner to be safe tho.

No personal offense meant here at all, but I simply don't believe you.  I've ran a cb550 with 14.2" shocks, 40 tooth rear sprocket/17 front.  It would easily rub.  Going to an 18 tooth front solved it.

With your stock rear sprocket, it puts the chain that much closer to the arm, probably over a half inch closer than my 40 tooth did.  PLUS, your swing arm angle is much more severe than mine with the 14.2" shocks.

You may have just enough clearance now, but you realize your chain doesn't stay still while moving.  It bounces up and down a lot, especially with engine braking when the tension is on the bottom half of the chain and the top half is flopping around.

You also have to realize, with the arm at that angle, when the suspension compresses and the arm levels out, it's basically increasing the distance from sprocket to sprocket.  THAT big of an increase will ruin your chain/sprockets, and possibly the countershaft, IF the chain isn't adjusted for the compressed position.  The downside is when not compressed, it's going to be pretty loose, and of course, contact the swing arm.

I'm just trying to save you some grief here.  There's a right way to do things, and a wrong way. 

[pirate4pleasure]

No I have clearance actually. I was looking at exactly that when I was designing it. I will also make a runner to be safe tho.

No personal offense meant here at all, but I simply don't believe you.  I've ran a cb550 with 14.2" shocks, 40 tooth rear sprocket/17 front.  It would easily rub.  Going to an 18 tooth front solved it.

With your stock rear sprocket, it puts the chain that much closer to the arm, probably over a half inch closer than my 40 tooth did.  PLUS, your swing arm angle is much more severe than mine with the 14.2" shocks.

You may have just enough clearance now, but you realize your chain doesn't stay still while moving.  It bounces up and down a lot, especially with engine braking when the tension is on the bottom half of the chain and the top half is flopping around.

You also have to realize, with the arm at that angle, when the suspension compresses and the arm levels out, it's basically increasing the distance from sprocket to sprocket.  THAT big of an increase will ruin your chain/sprockets, and possibly the countershaft, IF the chain isn't adjusted for the compressed position.  The downside is when not compressed, it's going to be pretty loose, and of course, contact the swing arm.

I'm just trying to save you some grief here.  There's a right way to do things, and a wrong way.

Ok well I guess I will put that back up on the drawing board. What would be the best solution to add as opposed to saying return everything to stock? I haven't dealt with tensioners before, just runners.

[TS250]

Well, at this point it'd probably be easier for you to get and mount a tensioner/roller.  I've never utilized one before, so don't know where to get one, but I would imagine ebay or any online motorcycle store would have one.  Maybe someone here will be able to point you in the right direction.  I also don't know if you really have enough room to jack the chain up with one, but I think you should.  Something to look into...

Of course, before you go through the trouble of all this, it might be good to ride it around for a bit to see if the changed geometry does anything you don't like to the steering.  I would imagine it'll steer quick.  Really quick.  So if it's too much to be comfortably streetable, you may end up having to lower the rear.

Just out of curiosity, could you measure the approximate distance from the old shock mounts on the swinger to the ones on the frame?

[lucky]

With the rear up, you have decreased the rake of the fork. The "angle of deflection" is now so steep, that hitting a bump simply caused the whole front end to go up, and then down, without pushing the lower leg into up its range on the tube. Maybe.

I'm no expert, and certainly your fork needs to be gone thru completely, a thorough flushing and the right weight of fresh oil, and non-sacked springs, but i think you'll still have to restore some rake to get it to feel right.

OCICBW

Looks nice though.

I agree, You have placed the lower end of the shock at the weakest point on the swing arm.  You have also decreased the rake by maybe 1º and the weight distribution has shifted forward. All of these changes are detrimental.