Bad Misfire on Faser

[headlamp]

My 2 year old Faser has developed a problem - it starts OK from cold, goes fine for a few miles but when it slows down and I have to go through the gears - it misfires, usually with one or two cylinders not catching & at idle sounds like an East German motorbike. Eventually after 10-12 miles everything clears itself and the bike is fine. Once going at high revs again, all the cylinders fire. It has just had uprated spark plugs, a service & have replaced the coils. Does anyone have any idea what my be causing this???


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[Gracie Jones]

Headlamp.

This is exactly what mine has been doing - 1999 model. I've put it down to the cold though.

they way to sort it is just to put choke on lots when starting, leave it idle for a minute or so, and then fiddle with the idle nob to make sure it is idling at about 1,200. If you do that, it should run ok.

Mine started doing this just after a service and just as the really cold weather hit. Have no idea what actually causes it though.

Luke

[MarJay]

Its classic carb icing.

Check that the carb heaters are not blocked, and try adding some fuel stabiliser to the petrol. I believe this helps with carb icing.

Basically, between 0 and 5 degrees C, the carb cools the air entering the intake enough to freeze the moisture in the air. This ice forms on the venturi tube of the carb and changes its aerodynamic shape. This decreases the effectiveness of the carburettor and eventually will lead to the engine missing and completely cutting out.

Leaving the bike to warm its own carbs with none of the cooling airflow sorts the problem, only for it to happen five miles later.

Less than 0 degrees C, the moisture in the air is already frozen and so cannot form on the venturi tube. Above five degrees the moisture doesn't get cold enough to freeze.

This does not affect fuel injected bikes because they work in a slightly different way.

HTH.
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Kickstart]

Hi

Does sound like carb icing to me as well. Suspect it suddenly starts to work after you land up going slowly for 5 minutes and heat filters through to the carbs.

Not sure on the Fazer what carb heaters are used. On the Divvy they were electric and triggered by a temperature sensor. However the heater was only in one float bowl, with pipes to the other float bowls.

I would try some additive designed to stop carb icing and see if that fixes the problem. If it does then have a bit more of a trawl for the real problem.

All the best

Keith

All the best

Keith
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