Yzf 600 cylinders 2 3 not firing

SOURCE: Rear cylinder not firing

The first thing I would do is replace the spark plugs again. You can foul a plug and it will cause you more problems than you can ever imagine. I see you have done all the logical things that I would recommend but I did not see you have replaced the plugs after the 200 miles. You would be surprised at how many times a $2.00 part can cause fits beyond belief.

SOURCE: 1979 suski 750,bike runs on 2 left side cylinders,

Hi and welcome to FixYa,

With the indulgence of craigjamesbt...

A few additional ideas to consider:

• it would be an electrical/ignition issue if 1 & 4 or 2 & 3 will not fire but not 3 & 4;
• almost always, raw fuel on exhaust indicates a flooded engine. A flooded engine would most likely be a carb issue;
• best way to determine if it is an engine concern is to do a compression test;
• a way to test the right carb pair is to deliberately starve them of fuel by temporarily plugging/blocking the inlet port/seat with rubber similar in appearance as to those used for glue gun, not installing the needle and float. Assemble the carb and install. Start the bike and use/spray carb cleaner on the right side carb. Note if 3 & 4 will fire even intermittently.

SOURCE: only running on 3 cylinders, nrew plug and clean

take the plus out and leave them in the boots lay them on a ground (bolt or the frame etc..) to make sure that there is no fire

SOURCE: 1982 GS850 Missing and Hesitation

fuel flow to cold pipe cylinder may be stopped with trash or sticky float.Resistor in plug wire for the one not firing could be bad. Try changing coil from one that is firing to the one thats not,see if that pipe gets hot or does the same thing still happen. coil ,plug wire, or fuel would be my primary focus.

Kelly

• 3740 Answers
• Posted on Jun 10, 2010

SOURCE: fzr 600 got killer spark pulls fuel valves in

This is not the news you probably want to hear but backfiring thru the carbs when you have good spark can be one of 2 things... either the valves are sticking / not closing properly due to carbon or the cam timing has shifted from the original position.

It would be best to do a compression test. You should have a minimum of 100 PSIG for an engine with major problems and up to 150 for a healthy engine. If you can not get 100 PSIG then it will be time for some serious engine service.

There is a possibility of the kill switch wire in the handle bar grip grounding under the grip to the handlebar but, since you said you have killer spark I doubt this is your problem.

Thanks for using FixYa.

Kelly

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