How to Rebuild a Motorcycle Carburetor

motorcycle carburetorRebuilding a motorcycle carburetor is something most people can do on a workbench with tools they already have with a little bit of the right knowledge.  Carburetors are not overly complicated devices, especially motorcycle carburetors.

Before we jump into how let’s talk about why.

Why would I need to rebuild my motorcycle carburetor:

  • Hesitation on acceleration
  • Hard starting while cold
  • The bike sat for a long time without running
  • Lack of power or poor fuel economy

Carburetors need to rebuilt under 2 circumstances.  First, if the bike sat for a long time with fuel in the carb the fuel can turn to varnish and clog small orifices or make things stick keeping your bike from running right.  This can cause hesitation on acceleration or hard starts when it’s cold.  The other reason you would need to rebuild a carburetor is if something inside has broken like a needle valve or float.  This would cause poor economy or maybe keep your bike from starting at all.

If your motorcycle carburetor needs to be rebuilt it’s important to know it’s a simple device but it’s much different than most carburetors on cars.  Most motorcycles use piston-type carburetors or constant velocity (CV) type carburetors.  This means they don’t usually have traditional choke flaps and the fuel bowl is below the throttle plate not next to it.  The good news is rebuilding these carburetors is just as easy as any carburetor rebuild as long as you have the right rebuild kit.

What to replace when rebuilding a motorcycle carburetor:

  • Any gasket you remove 
  • The needle valves
  • The float if it has fuel inside of it
  • Jets or venturis that are too clogged to clean

Also, remember to take note of all the settings of any mixture screws or choke adjustments before you take the carburetor apart.  If your bike ran well before you need a carburetor rebuild, setting it back to where it was is the best way to keep your bike running well.  If you’re having problems with cold starts and find your choke cable is sticky, check out our article on stuck choke cables to find out how to fix that problem.  Besides these tips, all you need is a carburetor rebuild kit, the right tools to disassemble your carb, and a notebook or camera to document how it came apart so you can put it back together the same way.

The last thing to note before you rebuild your motorcycle carburetor is that if your bike has multiple carburetors you will need to synchronize them after your rebuild.  This means you will want the throttle to open at exactly the same time on each carburetor and you’ll want to have the same mixtures throughout the power range on each carburetor.  If you don’t properly synchronize your carbs you could end up with a cylinder in balance which can lead to poor performance and stress on your engine.

If your bike is running poorly but you don’t have any reason to suspect internal damage to your carburetor you may consider simply using PJ1 Fuel Injector and Carburetor Cleaner to clean out any old gas or gunk causing components to stick to restore the performance of your motorcycle.  Using PJ1 Fuel Injector and Carburetor Cleaner can save the hassle of the rebuild as well as the task of synchronizing your carburetors.

Photo by Egor Myznik on Unsplash

2 responses to “How to Rebuild a Motorcycle Carburetor

  1. Excellent article I’m in between that I had someone rebuild it that obviously wasn’t qualified.
    I I have a 2004 Honda VTX 1300
    I’m looking for a metric mechanic Inland Empire close to Riverside or San Bernardino that can figure out what this guy did to my bike.
    I had the basic set during the pandemic carb had 20,000 miles on it it was idling rough but it ran.
    Now it hardly runs puke fuel and it caught fire thankfully I was in the saddle I just need my VTX fixed I’ve been on two wheels over 60 years I’m not going to burn on what I love to do.

    Any advice would be appreciated

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