How to rebuild the Honda CB450 K0-K2 & CL450 K0-K4 external spring forks – CMC Help Center

If you are not sure what forks are on your motorcycle, click here before to learn exactly what fork architecture you have.

This guide is applicable for these

models of Honda motorcycles

CB450 K0 - K2

CL450 K0 - K4

The CB450 K3-K4 uses a one-off fork style that we go a bit more in-depth on right here - Coming Soon

Before beginning this repair you need to remove:

Front-wheel

Front fender

When diving this deep into tearing down your Honda CB450 and CL450 Scrambler it is always a good idea to clean and rebuild things that are usually hard to get to. When the front forks are removed from the motorcycle you will have great access to the headlight ears, headlight bucket, front turn signals, triple trees, and steering bearing for cleaning and painting if they need it. We highly recommend taking the opportunity to either regrease the factory steering bearings or upgrade them to our tapered roller bearings. Find out how to do that right here:

Honda Steering Bearing Upgrade CB350 / CB360 / CB450 / CB550 Pt. 1: Disassembly

Honda Steering Bearing Upgrade CB350 / CB360 / CB450 / CB550 Pt. 2: Installation

Step 1: Remove the forks from the triple tree.

Loosen the bolts on the lower triple tree and remove the top caps that hold the fork tubes to the upper triple tree. You should then be able to pull the forks out down and out of the triple tree. It is common to find the top half of the fork tube rusty inside the headlight ears. If they do not easily slide out of the triple tree, use a hammer and wooden dowel to hammer the top of the fork tube until the fork begins to slide out. Do not hammer directly on the fork tube.

Step 2: Drain the fork oil.

With the forks removed, be careful not to turn them upside down with the top caps removed or the oil will spill out. Remove the fork spring seat and spring, then turn the fork upside down and drain the oil into an oil catch container. Pumping the fork tube back and forth will help remove as much oil as possible.

Step 3: Remove the fork tube and seal.

With the oil drained, remove the dust cover from the fork. Use snap ring pliers to remove the snap ring on top of the fork seal. You can then use the fork tube itself as a slide hammer to hammer the fork seal out of the fork lower.

Step 4: Disassemble the fork tubes.

The lower portion of your fork tube contains a few important pieces that are more important than you might think. The lower metal pieces of your fork are called the piston, dampener valve, and fork tube guide. They play a few roles including the dampening of the fork. All three pieces should be able to spin or move freely and should not be seized to the fork tube. The order and orientation of these are very specific so if yours are dirty or rusty and need to be removed for cleaning, snap a photo of the order and which way is up for each piece. They have a machined side matched to stop on the spring clips on the fork tube and must be put back together facing the exact way they did before they were removed.

Step 5: Inspect the fork tubes.

Before starting to clean up your fork tubes it's important to take a moment and thoroughly inspect them. For your new seal to function properly your forks need to be free of pitting and heavy wear on the chrome outer fork surface that moves in and out of the fork seal. Again, this only applies to the surface of the fork tube that travels in and out of the seal. Pitting and wear will tear up the new fork seal as well as let fork oil escape so if yours is bad, look for a set of good used condition fork tubes. If your tubes are in great shape where they travel in and out of the seal but the upper half is rusty, your tubes are completely functional and able to be reused. We generally remove the rust found on the upper half of most Honda fork tubes of this era and protect the upper half of the tube against future rust with a little clear coat.

Step 6: Clean everything.

Self-explanatory, right? We clean up the chrome with 0000 steel wool and wash it so it is completely free of grease and grime. If the upper half of the fork tube is rusty, wire wheel the rust off and add a thin coat of clear coat to protect it from future rust. Clean all aluminum pieces and internal pieces so they are grime and dirt-free.

Reassembly

Step 7: Reassemble the fork tube.

If you disassembled the piston, dampener valve, and fork tube guide, add a small coating of fork oil to each piece and reassemble in the order you removed them. If you forgot to snap a photo of the proper order, reach out to our support right here. Insert the fork tube back into the fork lower.

Step 8: Install the new fork seal.

There are two types of seals you can install into your forks, the EZ install brand seals and standard fork seals. Follow the guides below based on what style seal you are installing:

EZ install seals

The EZ install brand seals are great because they can simply be pushed into place. Be sure that the open side of the seal faces down and you place the included aluminum washer on top. These seals are supposed to float in the fork body and will expand when the fork is compressed and under load. With the seal pressed in just until it is underneath the groove, reinstall the snap ring. That's it!

Standard seals

The standard seals are installed by driving the fork seal into the lower body of the fork. This can be a bit tricky because you need to do this over the fork tube since it needs to be inside the fork while the seal is installed. To drive the seal into the lower fork body you will need either a single tube or pipe that fits over the length of the fork tube or a series of tubes that you can stack up to be able to hammer the seal in above the chrome fork tube. Be sure that the size of the tube you are using to drive the seal in is slightly smaller than the outer diameter of the seal. If it's too small you will risk damaging the inner seal surface, too large and you will run into the outer fork housing. Slowly tap the standard fork seal into place with your driver. You know you are done when the snap ring groove is right above the seal on all sides. Be careful to not drive the seal further than right below the surface of the snap ring groove.

Step 9: Add the fork oil.

In the Honda service manual, they call for premium quality ATF (automatic transmission fluid) but motorcycle fork oils have improved significantly since the '70s. You should now be using only a high-quality motorcycle fork oil in your forks. If you are a rider below 200 lbs. use 10w fork oil and if you are over 200 lbs. use 15w fork oil. Refer below to the exact amount of fork oil you need to add:

Fork Oil: 290cc (9.8 ozs.)

Use a graduated cylinder to make sure you have exactly the right amount.

Step 10: Finishing up the install

Once the forks are full of oil and ready to go on the motorcycle, reinstall your fork top caps so you do not spill the fork oil while reassembling the rest of your front end. Reinstall the headlight bucket, headlight ears, triple tree, and turn signals if you had removed them. Slide the spring and spring seat back onto the fork making sure that the tighter (progressive) windings face the top of the fork. Remove the top cap and slide the fork back through the dust cover, lower triple tree, headlight ears, and finally into the upper triple tree. Thread the top fork bolt through the triple tree and into the fork tube. Snug it up to secure the fork in place.

Torque the lower triple tree bolts to 21.7 - 28.9 ft-lbs. (29.4-39.1 nm)

Reinstall the front fender, front wheel, front brake cable, and speedometer cable. Re-adjust the front drum brake.

Torque the front axle holder nuts to 19-23 ft-lbs. (25-31 nm)