1979 cb750 fork rebuild; seem very soft

[sdew99]

Hey there, so I recently stripped down my forks and cleaned everything. I bought progressive springs off of vintage cb750 along with new seals. Contacted them and they told me to put the tighter windings at the top so I did. Put 5.8-6.0 oz of honda fork oil in as specified in the manual and the spacer that vintage cb750 sent with the springs and did not cut them as they advised.
Now, after putting them back together they seem extremely soft and I can hear what sounds like metal rubbing.
Any ideas? Not enough oil? Wondering if I missed something.

 

[mrtwowheel]

Did you check the upper tubes for straightness while you had them apart?

 

[mrtwowheel]

I'm going to take a shot at this. Concerning the spacers...........when you put the top back on the tubes was it hard to get it started, was it too easy, how much pressure was needed to compress the spring and spacer to get the top back on? I cut my own spacers from PVC pipe and make them as long as I can and still get the top back on.

 

[sdew99]

Did you check the upper tubes for straightness while you had them apart?

I didn't..

 

[sdew99]

I'm going to take a shot at this. Concerning the spacers...........when you put the top back on the tubes was it hard to get it started, was it too easy, how much pressure was needed to compress the spring and spacer to get the top back on? I cut my own spacers from PVC pipe and make them as long as I can and still get the top back on.

They seemed absurdly difficult to get back on. A lot of pressure to overcome to get it threaded. I drained the oil this weekend and re filled them to make sure the right quantity was in there and it doesn't seem any different. If you roll the bike and slam on the front brake, how far should the forks move? Mine seem to be dipping really far but idk what is normal..

 

[Old_Crow]

Hard for me to judge the softness of the forks on my current '79 CB750L because I'm coming off of 24 years of riding big Harleys, but I remember when I got my first '79 CB750L (back in the ' 90's) that the forks seemed really soft compared to the '72 CB 750K I'd been riding up to that point. I checked the fork oil at the time and just rode it.

 

[brettp]

Same here. I upgraded the springs on my 750 and it still feels too soft under hard braking. I will either get a thicker oil or add more of what's in there already if I decide to mess with it.
This is probably why some builders put R6 forks on their bikes.

 

[sdew99]

Same here. I upgraded the springs on my 750 and it still feels too soft under hard braking. I will either get a thicker oil or add more of what's in there already if I decide to mess with it.
This is probably why some builders put R6 forks on their bikes.

Do you guys find when the forks are compressed, you can hear the oil moving around? It's hard to explain, but if I push the bike up and down I can hear a 'sloshing' of the oil almost. I don't know know if this is normal as this is the first time I've spent time on forks.

 

[Old_Crow]

I'm in my 70's, and my hearing is shot. If I had the stock exhaust on the bike I probably couldn't hear it run.