CB450 fork rebuild... Advice?

[jammer415]

1972 CB450.

The fork is leaking fluid, so going to replace the seals, along with the fluid.

I read somewhere that it also helps to stack some washers on top of the springs when putting it back together as a way to stiffen up the spring rate a bit... Wondering if anyone else has experience doing this?

How many washers to stack up?

 

[jammer415]

Found an older thread that touches on this.

Wondering if anyone has experience with this washer/coin method of forming up the fork?


http://www.dotheton.com/forum/index.php?topic=33352.10



Thanks in advance for any insight.

 

[teazer]

The idea is to increase preload and get a little less sag. It's an old trick that racers did to stiffen up teh front end when they couldn't get springs that worked.

Don't just add washers or quarters though. Build the bike and measure the sag. If it's excessive see if you can get some slightly stiffer springs. If not, you may have to add a spacer on top of the springs. Depending on how much you need to add, it can be quarters/washers or a length of PVC conduit. That's what we use in race bikes.

 

[jammer415]

Ah ok, thanks a lot. I shall measure the sage first.

What is a good healthy amount of sag for inner city street use? (streets/potholes)

 

[teazer]

Static sag should be somewhere around 1/4 to 1/3 of total travel which in this case will probably be about 25-35mm I would think.

It's a place to start rather than an absolute rule. If there's too much sag, there's not enough fork travel for hitting bumps as you brake. If theer's too little the forks will top out over the smallest pot hole or dip in the road.

Typically with old forks, the springs have sagged and are too soft, so we end up with new springs and PVC pipe on top to get a good starting point. Modern forks have more travel, larger diameter springs and much better damping so they use thinner fork oil too. Ours have large damping holes, sagging springs and need 20 or even 30 wt oil to get them to work at all.

Most of our old forks can be made to work better with Gold Valve Cartridge Emulators to improve damping and better springs. Then add a fork brace to tie the legs together and stop them squirming.

For years I raced a Honda twin - a CB77 - with no front fork brace and teh front end would walk around on corners. In fact if I stood in front of teh bike with teh wheel between my knees, and grabbed the bars, it was easy to turn the bars quite far without the wheel moving. Took me a while to work out why it waltzed around corners like a pregnnat camel.