Motorcycle Tech: CB550 Fork Spring Upgrade

I recounted the tales of woe I experienced while riding this 1978 CB 550 to a two-day Kickstart Classic event in Alabama, within the CB550 rear shock upgrade. The suspension largely contributed to the woe in that tale and the ache in my back.

We upgraded the rear suspension by installing a set of Progressive Suspension 12 Series rear shocks and springs. In this issue, we’re installing a Progressive fork spring kit. The kit we’re installing is made specifically for this bike, but Progressive has tons of fork spring kits available for just about any make and model.

When deciding to upgrade the old or stock setup, there are several factors to consider: fork oil weight, progressive or standard springs (see step 8), or even rebuilding the entire fork. The front end on this bike had no oil leaks and moved nicely on the stock slides, so it didn’t require a complete overhaul. Not yet, at least.

Ride quality and perceived expectations from a new set of springs really come down to personal preference. I always refer to the owner’s manual or a well-trusted forum board to find the bike’s factory specs, then build off the stock platform. In this case, the old CB had a bouncy front end and tons of chatter. So, I wanted to slow down the rebound and soften up the forks. I used a new set of springs that were close to the factory spec, but a heavier-weight fork oil.

An important thing to note is that fork springs are under a tremendous amount of pressure, and the energy stored in a compressed spring can really pack a punch. So be aware of this and use caution when removing fork caps. Elevate the front tire and stay out of harm’s way when doing this. Enough talk—let’s get started on part two of the CB suspension upgrade.

10mm ratchet
S12mm ratchet
Adjustable wrench large

Progressive Suspension
Fork spring kit $97/#11-1106

Spectro Performance Oils
Spectro Fork Oil $12.99/SAE 10

Like we did in the rear shock installation (issue 219), prop up the bike, this time keeping the front wheel off the ground.
Remove the handlebar using a 12mm ratchet.
Remove the fork tube cap. We used an adjustable wrench to do this. The cap will be under pressure from the stock fork spring, so remove this with care, and keep your face well off target.
Remove the stock springs. The old coil should be easily accessible, no tools required.
Drain the old fork oil by removing a drain plug located on the bottom of each fork leg with a 10mm ratchet.
With the top fork cap and bottom drain plug removed, spray a fork oil cleaner like Spectro’s Suspension Cleaner in both the top and bottom of the tube, flushing out any built-up oil residue. You can also run an appropriately sized pipe brush through both tubes.
After both fork tubes have been cleaned and fully dried, reinstall the stock drain plug and copper crush washer.
Drop the new Progressive springs into each fork tube. As you can see, these coils get tighter at the top, making them progressive. If you’re installing springs like these, make sure the progressive end is at the top.
Add new fork oil. Check your owner’s manual for the appropriate oil weight and amount to add. We’re using a 10w Spectro fork oil and measuring using the bottle’s built-in graduated marks.
Reinstall the stock fork caps. This requires a bit of pressure. Take care not to cross-thread the caps when doing this; first rotate the cap counterclockwise until you feel it drop onto the threads, then tighten to the appropriate spec.
Reinstalling the handlebars with stock hardware using a 12mm ratchet.
This CB’s re-spring is completed and ready for the road. RC

Motorcycle Tech: Honda CB550 Rear Shock Upgrade

Back in 2011, I bought a 1978 CB550 to ride on the inaugural two-day Kickstart Classic event. The official ride started at Dale’s Wheels Through Time in Maggie Valley, North Carolina, and finished at the Barber Motorsports Park in Birmingham, Alabama. This event was hosted by American Iron Magazine but open to all makes and models, so the American kickers welcomed my Honda.

This event is organized for any bike with a manual kickstart, although the lazy electric-start bikes are also welcome. In the time leading up to the event, I didn’t own a kicker, so I picked up a vintage Honda from eBay. I was told it was a gem and ran great. However, the seller’s idea of “runs great” and mine varied a bit.

I had three months to prepare the bike for long-distance travel. Steve Lita, then editor of AIM and GB, and I decided that we’d ride from AIM’s headquarters in Stamford, Connecticut, to Alabama and back—all or bust.

Over those three months, I went over as many of the mechanics as I could, while bobbing and chopping the bike up into a tight little café: Clubman bars, as cool as they look, were a bad choice. That decision bit me in the lower back two hours into our six-day journey south. I had also overlooked making any upgrades to the suspension, which really should have been addressed. Live and learn.

To make a very long and backbreaking story short, the little Honda and I made it to Alabama, but the engine gave all it could on the ride down. We both rode home in a pickup truck.

It’s taken a while, but I’m resurrecting the old CB from a corner of the shop where it’s sat since 2011. I’m starting with a two-part install of Progressive rear shocks and fork springs. This is part one, the installation of Progressive 12 Series shocks and springs, a comprehensive shock and spring set that includes all the necessary hardware that you’ll need to fit a variety of bikes.

14mm ratchet/torque
Shock spring compressor
Flathead screwdriver
Blue Locktite

Progressive Suspension
12 Series shocks
12 Series springs

Honda CB550 Rear Shock Upgrade
A look at the Progressive Suspension 12 series shocks and springs before assembly.
Honda CB550 Rear Shock Upgrade
Here are the original 1978 shocks.
Honda CB550 Rear Shock Upgrade
Prop up the rear tire to allow for adjustment when fitting the new shocks.
Honda CB550 Rear Shock Upgrade
Remove the old shocks using a 14mm socket or impact driver and save original hardware. Penetrating oil may be needed to loosen the nuts and bolts.
Honda CB550 Rear Shock Upgrade
The bump rubber and washer may need to be lubed in order to move down the piston shaft, making room for the spring assembly.
Honda CB550 Rear Shock Upgrade
A flathead screwdriver assists in moving the bump rubber and washer.
Honda CB550 Rear Shock Upgrade
Install one new shock without the spring and check the clearance between the tire and fender by raising the rear wheel until the shock bottoms. There should be a minimum of 1″ of clearance.
Honda CB550 Rear Shock Upgrade
Assemble the springs onto the shocks using a spring compression tool. This tool will be needed and many options are available for a variety of spring and shock sizes. For this installation, we used a simple lever compression tool.
Honda CB550 Rear Shock Upgrade
A look at the fully assembled shock with the spring retainer clip and top cap in place.
Honda CB550 Rear Shock Upgrade
Supplied spacers were needed for this install when hanging the new shocks.
Honda CB550 Rear Shock Upgrade
Install the new, fully assembled shocks using the original nuts and bolts, lock washers, and provided washers. A little blue Loctite can be applied to the bolts.
Honda CB550 Rear Shock Upgrade
Here’s a look at the new shocks installed and standing proud. RC