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I am facing poor fueling with my carburetor in my 2011 Yamaha Fz 16. What are there trivial trouble shooting checks I need to do to diagnose the issue??

Edit: When ever I am driving in low RPM, I feel like the fuel is cut off in short sharp intervals. And even with the Idle RPM adjuster screw cranked up to the max my idle RPM is very low that my engine turns off when I close the throttle.

  • Welcome to the site! Can you elaborate on the symptoms you are experiencing that lead you to believe it is a carburetor issue? – MooseLucifer Jun 29 '16 at 13:19
  • @MooseLucifer added my symptoms in edit. – gman Jun 29 '16 at 13:28
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    Related: mechanics.stackexchange.com/questions/26022/… The general approach would be similar. – Chenmunka Jun 29 '16 at 14:35
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    @Chenmunka Since the question you linked (excellent answer, btw) is not quite a duplicate, I think you can/should edit and post it as an answer this question. – MooseLucifer Jun 29 '16 at 15:03
  • Thanks for the comment and copy suggestion - happy to oblige. – Chenmunka Jun 29 '16 at 15:15
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These symptoms are typically caused by one or more blocked jets in the carburettor.

Small particles of grit can block any one of the jets in carburettors. The fuel still gets to the engine through the other jets but the efficiency is much degraded. The number and size of the jets varies by model.

I have no experience with Yamaha motorbike carbs but I have seen this problem on various old cars.

You have two approaches:

1) On some older carburettors there will be a connector where you can connect a tyre pump and give a blast of air to clear the grit.

2) The jets easily unscrew, so you can blow through them individually. You will have to take the top off the float chamber to access some of them, this is just a matter of half a dozen screws. The float is connected to the top and will lift out as you remove the top. While you have the float chamber exposed, it is worth checking if there is grit sitting at the bottom. If so, wipe it out with a cloth.

The symptoms you describe - stalling at idle - suggest that the Idle Jet is the one that is blocked. This is visibly smaller than the main jet and is therefore more prone to blocking in this manner.

  • Thanks @chenmunka. Will try this and post a full diagnostic story. – gman Jul 1 '16 at 6:20
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There are quite a few things that can effect your bike in this way

First, you need to truly identify the issue. Before you tear down your carburetor you may want to engage in some troubleshooting prior.

You said

When ever I am driving in low RPM, I feel like the fuel is cut off in short sharp intervals. And even with the Idle RPM adjuster screw cranked up to the max my idle RPM is very low that my engine turns off when I close the throttle.

This might not be your carburetor. It could be ignition related and that may not be the root cause either. These types of issues can crop up with a bad battery OR a failed/failing rectifier.

If you have a multimeter you can perform some simple tests to ensure that your charging system and rectifier are in good shape.

Try this rectifier and stator test first. It's simple and quick. As well, test your battery under load.

Here is a post that can give insight regarding your carburetor and if it's experiencing a rich or lean condition.

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