Ignition Condenser | Honda CB500K / CB550 / CB750
Your bike idles fine but won't rev past 5,000 RPM? One cylinder drops out under load? The ignition condenser is the most common failure point in the whole ignition system on the CB500K, CB550, and CB750 — and the best news is it's a cheap, ten-minute swap once you have the right part in your hand.
Why You Need This
The condenser has a simple job: keep the ignition coil charged under high-speed conditions and protect the contact points from premature wear. Even though it has no moving parts, the condenser is an electrical component that decays with age. After forty-plus years, most condensers on vintage Honda fours are either already dead or on their way out.
When a condenser starts failing, the bike will usually idle normally and run fine at low speeds, but hit a wall around 5,000 RPM where it bogs hard or drops to three cylinders. Our knowledge base article "Engine Fires on One Cylinder — Is my Condenser Bad?" walks through the exact symptoms, and our condenser test article shows the quick visual check you can do in about five minutes.
Specifications
| Spec | Detail |
|---|
| Replaces OEM Part Numbers | 30250-300-154, 30250-300-005 |
| Fits Models | CB500K (1971–1973), CB550K (1974–1978), CB550F (1975–1977), CB750A (1976–1978), CB750KA (1977–1978), CB750FA (1977–1978) |
| Sold As | Pair (two condensers — one full set for a single bike) |
Important — sold in pairs. Every four-cylinder Honda in this family uses two condensers — one for the 1-4 contact breaker and one for the 2-3 contact breaker. One "set" is two condensers, which is exactly what one bike needs. If you have two bikes, order two pairs.
Does NOT fit CB500T. The CB500T is a parallel twin that shares its ignition with the CB450 and CL450 — a completely different condenser assembly. Make sure your bike is the four-cylinder CB500K (1971–1973), not the twin.
How to Test if Your Condenser is Bad
Two quick tests, no specialty tools required:
- The RPM wall test: Start the bike and warm it up. Try to rev past 5,000 RPM in neutral or ride through the gears. If the bike bogs hard, stutters, or drops to three cylinders anywhere around that RPM range, a failing condenser is the prime suspect.
- The dark garage spark test: Roll the bike into a dark space. Remove the point cover so you can see the contact breakers. Start the bike and watch the points as they open and close. A healthy condenser shows only a small intermittent spark every few seconds. A failing condenser shows a bright, persistent spark at the points every time they open — that spark should be inside the condenser, not at the points. See our full bad condenser test article for photos.
Installation
Difficulty: Beginner
Tools needed: Screwdriver or allen key (depending on whether your bike has the factory JIS screws or our allen-bolt conversion), spade connector pliers if the leads are corroded.
- Remove the point cover on the left side of the engine at the crankshaft.
- Locate the two condensers — they mount on the back of each contact breaker, wired to the points primary terminal with a short lead.
- Disconnect the primary lead from the points terminal on the first condenser.
- Unscrew the mounting bolt (or JIS screw, if you haven't converted yet) and lift the old condenser out.
- Mount the new condenser, reconnect the primary lead to the points terminal, and tighten the mounting bolt.
- Repeat for the second condenser on the opposite contact breaker.
- If you're doing a full tune-up, it's worth replacing the contact points at the same time (they're also a wear item) and converting to our allen-bolt mounting kit so the next replacement is a breeze.
Our walkthrough on ignition timing for the CB500K/CB550/CB750 covers point and condenser replacement as part of the full tune-up procedure. Worth watching start to finish before you pop the point cover the first time.
Frequently Asked Questions
How many condensers do I need for one bike?
Two. Every CB500K, CB550, and CB750 in our fitment list uses two contact breakers (one for cylinders 1-4, one for cylinders 2-3), and each breaker has its own condenser. One "pair" from this listing is exactly what one bike needs. The system is sold in pairs by default so you don't end up with a bike running one old condenser and one new one — replace them together.
Can I replace just one condenser if only one side is bad?
Technically yes, but we don't recommend it. Condensers are a wear item that fail from electrical decay over decades, so if one side has failed the other is usually close behind. You're already inside the point cover — doing both at once saves you from pulling the cover again in six months. The pair price is reasonable enough that it's not worth the risk.
Will this fit my CB500T?
No. The CB500T is a parallel twin that uses a different ignition assembly shared with the CB450 and CL450. This condenser fits the four-cylinder CB500K only (1971–1973). If you're on a CB500T, you want our CB450/CB500T parts instead.
How long do condensers last? Do I need to replace them on a schedule?
There's no fixed service interval for condensers the way there is for contact points (which CMC recommends inspecting every 1,500 miles). Condensers either work or they don't — replace them when symptoms appear (the 5,000 RPM wall or the bright spark at the points in the dark garage test), or proactively during a full ignition tune-up. At 40+ years old, any untouched factory condenser is a valid candidate for replacement regardless of current symptoms.
Should I replace the points at the same time?
If your points look pitted, worn, or if you haven't replaced them recently, yes. Our Ignition Point Set covers both 1-4 and 2-3 points in one purchase, and you're already inside the point cover. If you want one box that bundles points, condensers, and our allen-bolt conversion, grab the Ignition Rebuild Kit instead.
You Might Also Need
For the full timing procedure after a condenser replacement, see our How to set the ignition timing on the Honda CB500K / CB550 knowledge base article.
Last updated: April 2026
