How Do I Know When My Carburettor Needs Cleaning?

If your bike, mower, or classic car isn’t running quite like it used to, your carburettor might be quietly crying out for help. The carb (short for carburettor) is a beautifully simple yet surprisingly fussy piece of engineering — and when it gets dirty, your engine knows about it.

But here’s the tricky bit: how do you know when your carburettor needs cleaning?

That’s exactly what we’re going to answer in this guide. Along the way, we’ll cover the signs to watch for, the difference between a quick clean and a deep ultrasonic clean, and why ignoring a dirty carb can cost you more than just performance.

Oh, and if you decide your carb could use some TLC, we offer professional ultrasonic carburettor cleaning at a great price — go to our homepage to see our carb cleaning service and get your engine back to its best.


 

Before we talk about cleaning, let’s remind ourselves what a carburettor actually does.


Whether it’s a motorcycle carburettor, a lawn mower carburettor, or even a high-performance Mikuni carburettor or Keihin carburettor, the basic principle is the same:


  • The carb mixes air and fuel in just the right ratio.
  • The engine then burns that mixture to produce power.



There are many carburettor types, from simple slide carbs to more complex CV carbs (constant velocity carbs), but they all share a fatal weakness — they hate dirt. Tiny jets and passages can be blocked by fuel varnish, dust, or debris, and when that happens, everything from idle smoothness to full-throttle performance suffers.

7 Signs Your Carburettor Needs Cleaning

If you notice any of these symptoms, it’s time to think about giving your carb a good clean — ideally an ultrasonic cleaning for the deepest results.


Hard Starting


If you’re cranking the starter over and over before the engine finally coughs into life — or refuses to start at all — your carbs may be clogged. Fuel isn’t flowing properly, and that’s a red flag.


Rough Idle


A healthy bike carburettor should idle smoothly. If it’s hunting, surging, or stalling, your idle jet or air passages could be gummed up with fuel varnish.


Hesitation on Acceleration


You twist the throttle and… nothing. Or at least nothing for a second or two before the power arrives. That hesitation is often caused by blocked jets or sticky slides inside the CV carbs.


Poor Fuel Economy


If your engine is suddenly drinking more fuel than usual, the carburettor may be letting too much petrol into the mix due to a dirty or sticking float.


Black Smoke from the Exhaust


Black smoke = too much fuel. A dirty Keihin carburettor or Mikuni carburettor can upset the air/fuel ratio, making your engine run rich.


Loss of Power or Top Speed


When your carburettor can’t breathe properly, neither can your engine. If you’ve lost your top-end power, you might need more than just a new spark plug — you probably need an ultrasonic clean.


Engine Dies Under Load


You open the throttle under load, and the engine cuts out. This is often the sign of blocked main jets or fuel starvation caused by carburettor contamination.

Why Ultrasonic Cleaning Works Best

Sure, you can spray carb cleaner into your carburettor and hope for the best. And yes, it might even improve things temporarily. But here’s the problem: that method only cleans what you can see.


An ultrasonic cleaner uses high-frequency sound waves in a heated cleaning solution to remove dirt, varnish, and carbon from every nook and cranny — even inside tiny fuel passages that no brush or spray can reach.


When we perform an ultrasonic carburettor cleaning:


  • The carb is fully disassembled.
  • All jets, screws, and passages are placed in the ultrasonic bath.
  • Cavitation bubbles scrub away dirt at a microscopic level.
  • The carb comes out looking and performing like new.



If you want the best carburettor performance possible, ultrasonic is the way to go. It’s the gold standard for cleaning everything from a lawn mower carburettor to a high-end race bike carburettor.


And yes — we offer this service at a price that will surprise you. Click here to book an ultrasonic carb cleaning today.

Carburettor Types and Their Cleaning Needs

Different carburettor types have slightly different cleaning requirements:

• Slide Carbs – Simple design, easy to strip, but still benefit massively from ultrasonic cleaning for deep jet cleaning.

• CV Carbs – More complex, with diaphragms that need careful handling. These are especially prone to dirt affecting throttle response.

• Mikuni Carburettor – Common on performance bikes, with precision-machined jets that must be kept spotless.

• Keihin Carburettor – Known for efficiency and reliability, but the tiny air bleed passages easily clog.

• Lawn Mower Carburettor – Often neglected until the mower won’t start. A quick clean can bring it back to life.


We clean them all — from vintage carbs to modern performance models — using professional ultrasonic cleaning methods.

DIY vs Professional Carb Cleaning

You might be tempted to clean your carb at home. And for a quick fix, a spray can of carb cleaner and some basic tools can help. But here’s why professional ultrasonic cleaning is worth it:


  • Thoroughness – DIY cleaning can’t reach every internal passage.
  • Safety – Delicate parts like diaphragms can be damaged by aggressive cleaning.
  • Time – Stripping, cleaning, and reassembling carbs can be a long, fiddly job if you’re not experienced.
  • Results – An ultrasonic cleaner leaves no hidden dirt behind.



If you want the job done once, and done right, let us take care of it. See our carburettor ultrasonic cleaning prices here.

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How Often Should You Clean Your Carburettor?



If you ride regularly and use good fuel, a clean every 12–18 months is usually enough. But if your bike or mower sits unused for months at a time, the fuel inside the carbs can break down into sticky varnish surprisingly quickly — sometimes in just a few weeks.


Tip: If you’re storing your bike over winter, drain the motorcycle carburettor float bowls or run the engine dry to prevent blockages.





The Cost of Ignoring a Dirty Carburettor



Neglecting a dirty carb isn’t just bad for performance — it can damage your engine. Running lean (too much air, not enough fuel) can cause overheating and internal damage. Running rich (too much fuel) can foul spark plugs, wash oil from cylinder walls, and clog your exhaust.


In short: a dirty carb can cost you more than just the price of cleaning.

Our Professional Carb Cleaning Process


  1. Inspection – We identify the carburettor type and check for worn parts.
  2. Disassembly – Every jet, screw, and float is removed for separate cleaning.
  3. Ultrasonic Cleaning – The parts are bathed in our heated ultrasonic cleaner until they’re spotless.
  4. Reassembly – Using correct torque and fresh seals where needed.
  5. Testing – To ensure your carb performs perfectly before it’s returned.



Whether it’s a Mikuni carburettor, Keihin carburettor, lawn mower carburettor, or a vintage twin carb setup, we treat every job like a restoration project.

Final thoughts

Knowing when your carburettor needs cleaning isn’t rocket science — the signs are there if you know what to look for. Hard starting, rough idle, poor fuel economy, loss of power, or black smoke are all indicators your carbs need attention.


When that time comes, remember:


  • A quick spray can help, but it’s only temporary.
  • Professional ultrasonic cleaning is the most effective way to restore performance.
  • We offer expert carb cleaning at a great price, for every carburettor type from CV carbs to performance Mikuni carburettors.



Your engine will thank you — and so will your wallet in the long run.

Book your ultrasonic carburettor clean now and feel the difference.