Bike Won’t Start? How Carb Issues Could Be the Real Problem

If you've ever twisted the throttle, heard the starter click, but still your bike refuses to fire up, don’t assume it’s always electrical. Often, the problem lies in your carbs. Dirty carbs, flooded carbs, or misadjusted float height are frequent culprits. Here’s how to diagnose and fix them.

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What to check when your bike won’t start

  • Fuel reaching the carb: Make sure fuel is flowing freely, petcock isn't clogged, and fuel lines are clean. Old fuel can leave varnish that blocks jets.
  • Flooding: If the float valve is worn or stuck, “carbs flooding” happens—fuel over‑fills the bowl. Bike may smell of petrol, plugs will be wet.
  • Dirty jets and pilot jet blockages: Even small bits of debris in the pilot jet can stop the bike from idle, stall under throttle, or fail to start without choke.

How to fix it

  1. Remove carb(s), clean thoroughly. Use carb cleaner and compressed air.
  2. Check float height. If float height is too high, you’ll get flooding; if too low, fuel starvation.
  3. Replace any worn seals, gaskets, or float valve parts.
  4. Reassemble carefully, checking for air leaks at boots and intake manifold.
  5. If issues persist, an ultrasonic carb clean might be worth it — it reaches passages that sprays or manual cleaning can’t.

When to Ask a Pro ?

If you’ve tried cleaning and checking float height but the bike still won’t idle, starts only with choke, or dies under throttle: it’s probably time for a full carb rebuild.

At The Carb Shack, we specialise in carb cleaning, carb rebuilds, float height adjustment, and ultrasonic carb clean. If you're in Kent or London (or nearby), get in touch — we’ll help you get your bike starting strong again. Check our Motorcycle Maintenance Blog for related posts or our Q&A Hub if you have specific carburettor questions.

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