What a valve spring compressor does
A valve spring compressor tool lets you safely compress valve springs so you can remove and reinstall the valve keepers (also called valve locks). Once the keepers are out, you can remove the springs and pull the valve out of the cylinder head for inspection of the valve, valve seat, and valve guide.
This is the proper tool for the job on any vintage Honda cylinder heads that use coil valve springs. It will also perform the same job on most other cylinder heads using a coil valve spring. This one tool covers a lot of makes and models because it includes multiple adapter sizes and a clamp-style frame.
The demonstration cylinder head in this video is a Honda CB350 twin cylinder head, however the same method would apply for the other models in the CT90, CB100, CB125, CB175, CB200, CB360, CB500K, CB550K / CB550F, CB750K / CB750F families of motorcycles.
Valve springs are under high tension. If the tool slips or a keeper pops loose unexpectedly, small metal parts can fling out. Wear safety glasses or proper eye protection any time the spring is being compressed or released.
Tools and supplies you’ll want on the bench
Valve spring compressor tool with multiple adapters
Magnet pick-up tool (recommended for keeper removal/installation)
Needle-nose pliers (backup option to the magnet)
Engine oil (for valve stem lubrication during assembly)
A small amount of engine grease (to “stick” keepers in place during assembly)
Cylinder Head Stand, Wood blocks, or 2x4s
Small file (only if the valve stem tip is mushroomed and the valve sticks in the guide)
How to support the cylinder head for valve removal
You need access to the valve from both sides of the cylinder head:
The compressor pushes on the retainer from one side.
The tool’s lower contact point centers on the valve from the other side.
Support the head on a cylinder head stand or blocks so the combustion chamber side (or the spring side, depending on your setup) is raised enough to position the tool underneath without the valve contacting the bench.
Goal: The head sits stable, doesn’t rock, and gives you clearance to clamp the tool straight.
How to choose the correct adapter
Our valve spring compressor kit includes different diameter “cups” or adapters that contact the retainer.
Identify the retainer (the round piece at the very top of the valve spring assembly).
Test-fit adapters over the retainer.
Choose the adapter that sits squarely and covers the retainer well without slipping off.
How to remove a valve spring and valve
1) Set up the compressor tool
Most clamp-style valve spring compressors function like a large C-clamp with threaded ends.
Assemble the threaded sections (a light coat of oil on the threads can make it turn smoother).
Install the chosen adapter on the side that will press on the retainer.
-
Position the tool so:
The lower contact point is centered on the valve.
The adapter is centered on the retainer.
2) Compress the spring
Tighten the tool slowly until you feel spring pressure.
Continue compressing until the keepers are free and accessible. Work slowly and keep the tool aligned. If anything shifts, back off and re-center.
Removing the valve keepers (locks)
Valve keepers are two small split pieces that lock into the groove on the valve stem.
With the spring compressed, use a magnet to lift out the first keeper.
Remove the second keeper the same way.
Keep the parts together for each valve (a tray or labeled bags helps). Replacement valve keepers are extremely difficult to find replacements for.
Releasing spring pressure safely
With the keepers removed, hold the tool stable and back off the tension slowly.
Remove the retainer and springs.
Slide the valve out of the valve guide in the cylinder head.
If the valve is stuck in the guide
Sometimes the valve will slide partway out and then stop. A common cause is a slightly mushroomed valve stem tip from the rocker arm contacting it over years of use.
What to do:
Do not force the valve through the guide.
Inspect the tip of the valve stem for a raised edge (a “high spot”).
Use a file lightly around the edge to remove only the high spot.
Test the valve in the guide again and repeat lightly as needed until it slides out smoothly.
Important: Forcing a stuck valve can damage the valve guide.
Valve spring and valve parts explained
Below is the typical stack-up you’ll see on many vintage Honda cylinder heads. The CB350 twin cylinder engine shown in our video does not use valve stem seals, however most of the models from this era do use a valve stem seal.
Valve assembly parts (top-end rebuild reference)
| Part | Also called | Notes |
|---|---|---|
| Valve | Intake valve / exhaust valve | Slides through the valve guide; stem has a keeper groove near the top. |
| Valve stem seal (if equipped) | Stem seal | Not used on the CB350 twin in the video; used on some other Honda engines. |
| Inner spring | Small spring | Progressive-wound; tight coils oriented downward in the video. |
| Outer spring | Large spring | Fits over the inner spring; tight coils oriented downward in the video. |
| Retainer | Spring retainer | Top cap that the compressor pushes on; captures the keepers. |
| Valve keepers | Valve locks | Two-piece tapered locks that seat into the stem groove. |
| Spring seat | Spring base | Hardened seat surface in the head; often stuck in place. |
How to reinstall the valve, springs, retainer, and keepers
1) Install the valve
Lightly oil the valve stem.
Insert the valve into the guide.
Push the valve up so it sits on the valve seat.
2) Install the seal (if your engine uses one)
If your engine uses a valve stem seal, install it now:
Oil the seal lightly.
Slide it onto the valve stem and seat it properly.
3) Install the springs and retainer
Install the inner spring.
Install the outer spring.
Place the retainer on top.
4) Compress the springs
Position the compressor: bottom centered on the valve, adapter centered on the retainer.
Tighten slowly until the keeper groove is clearly exposed.
You generally do not need to compress “all the way”—only enough to install the keepers.
Grease trick for keeper installation
A small dab of grease helps the keepers stick in place while you position them.
Put a small blob of grease at the groove where the keepers will sit on the valve stem or on the cupped inside of each valve keeper.
Use a magnet to place the first keeper into position.
Place the second keeper and align both halves.
Needle-nose pliers can work, but a magnet is usually easier and more controlled.
Final keeper seating checks before releasing tension
This is the most important part of the entire process.
Before releasing spring tension:
Confirm both keeper halves are centered and seated in the valve stem groove.
Keepers should look even (not cocked, crooked, or at different heights).
Then:
Release spring tension slowly.
Watch the keepers as the retainer comes up and captures them. There should be no gap between the retainer, keeper and the valve stem. The two keepers typically do not cover the full circumference of the valve stem; small gap between the vertical edges of the two keepers is normal.
After tension is released, verify the keepers sit evenly and appear the same height.
If anything looks off: Re-compress, re-seat the keepers, and try again. If a keeper is not properly seated and you release tension, it can shoot out.
FAQ
What is a valve spring compressor tool used for?
A valve spring compressor, compresses the valve spring so you can remove and install the valve retainers and keepers. This allows the engine valves to be removed for valve seat and valve guide inspection or rebuild work.
Do I need a valve spring compressor for a vintage Honda engine rebuild?
If the cylinder head uses coil valve springs, yes—this is the correct and safe way to remove and install the valve spring/keeper assembly. the exception is the Honda CB450 / CL450 /CB500T DOHC engines, see below.
Will one valve spring compressor fit multiple motorcycles?
Most clamp-style valve spring compressors include multiple adapters and can work across many cylinder heads, as long as the engine uses coil valve springs.
Are there engines that do not use this style tool?
Yes. Some Honda DOHC (dual overhead cam) cylinder heads like the CB450, CL450, and CB500T use a torsion-bar valve spring design rather than coil springs; this tool is not used for this design.
Purchase a Valve Spring Compressor Tool Here