Tuesday, May 13, 2008

Forks Rebuilt

I have two Honda CB700SC's, one I am rebuilding and one I pieced together and is my daily driver. Since I had rebuilt that bike I have had leaks in the front forks, and they are getting worse. I decided over the past weekend that I would rebuild the forks and replace not only the fork seals but the springs as well. I completed the job and it was worth the effort as my front end is now very firm and not loose at all, and it really responds well to a quick stop.

I started by getting together the tools I would need for the job. The main tools were the tool to hold the fork innards when removing the base nut. Also I would need a seal driver. I would also need all of the parts required, which luckily I had acquired after many months of scrounging and a last-minute spree at Dennis Kirk.
I started with the right fork and had that apart in no time. The seal came out and the fork came apart easily, but I needed to use the special tool to hold the innards to remove the base nut. I made this tool out of a piece of 5/8 inch threaded bar and then the nuts at the hardware store that would fit on it. I bough three feet of rod, two nuts, and a lock washer. On one end of the bar I attached the two nuts with the lock washer between them, and then tightened them as much as possible. This being done I inserted the tool into the fork and it found a connection on the inner damping rod. A picture of the tool in the damping rod is below. I also needed to drive the fork seal on, and for that I used a 1-1/2 piece of PVC to do the job. It fits right over the 39mm forks and drives the seal well. I used a 2 foot piece.

So much for buying tools you will only need once. Lastly in the tool dept. I needed to have something to measure the fluid level in the forks, so I devised a syringe and rod with a tube to do that. I measured the desired height and marked it on the rod, and then held the tool at that height until I was sucking air out of the forks.

I purchased a set of Progressive front fork springs and also bought Leak-Proof Moly Seals for the fronts. There are pic's below. Notice how much longer the Progressive springs are compared to the stock. They are a thicker spring and provide for a firmer ride.

Once I got the right forks back together I did the left forks. As you can see there are alot of parts to the left fork on this bike. And this is without the small piston that is still in the lower part of the fork. It was a small miracle when that finally came out.

Once I got the forks back together I installed them and then took the bike for a test ride. I have put about 200 miles on the upgrade and I must say I am very very happy. The old springs gave you no sense of comfort during an aggressive stop. The new forks are great and much more firm. I didn't drain much fluid out of the forks, so I am guessing they were fairly low compared to the spec's for the forks.

I also replaced the fork fluid with Mobile 1 ATF instead of standard ATF. I have read it has similar viscosity properties to a 10-weight fork oil, but is much more stable being a full synthetic. I am glad anyway as the ride is more firm and since I am a heavier rider it makes a big difference. I think the next mod will be the Progressive Suspension series rear springs and shocks.

On a final note I have received my parts back from the powder coater, and they look amazing. I will post some pic's when I get a chance. You have to see the brake calipers - unbelievable.

Thanks, Y'all



levent said...

Thanks for the tip about the 5/8 rod, I just dismantled my bike forks using the same method.

Sean Durkin said...

Thanks a lot, I used the tools you suggested all for $10. I wouldn't have tackled this project without your post so thanks again!


kineticgraphics said...

What size nuts did you use on the 5/8ths rod? Are they 24mm?