3rd cylinder cold - blocked air passage ?

[siedlik]

Hello,


There are 2 holes in front of the carb, is there a screw or jet that could be blocked? As the 3rd cylinder is cold at idle, but it's fine when going above 5000rpm.
I did rebuild the carbs, but not sure if I've seen a screw in one of those holes. Will have to take the carbs out again  :rolleyes

https://youtu.be/I0siKsK6CfM?t=116

Just found a video and looks like that could be the issue.
Thanks

[unfazed]

Would be highly unusual to have an air jet blocked unless you ran it with out an air filter or maybe placed the carbs on a dirty bench.I would double check the pilot jets and the air screw settings.The pilot jet do not have a clean hole but a web design internally and can be notoriously difficult to clean if badly clogged by old fuel lacquer

[BBROWN1664]

sounds like a blocked idle jet

[siedlik]

Nothing looks blocked.
Idle screw was about 3 turns before rebuild, but I decided to do 2,5 as in the manual. Would that make one cylinder not idle?
Will try 3 turns and put the carbs back.

[BBROWN1664]

Nothing looks blocked.
Idle screw was about 3 turns before rebuild, but I decided to do 2,5 as in the manual. Would that make one cylinder not idle?

Blocked idle jet - my money is on this still
Poor connection on HT lead

[unfazed]

Could you see through the pilot jet? Did you clean the carbs and jets  in a Ultrasonic bath or by hand? If by hand, what did you clean them with?

[siedlik]

I have compared the idle jet with others, and they are the same. I even swapped them.
I have swapped HT leads with 2 and 3 cylinder, new spark plug, new cap plug. Still the same.
So I got Compression, I got Spark, I think I only miss fuel on idle. The bikes run fine on a high rpms, its just that 3rd cylinder is not idling.


The pilot jet screw on that 3rd cylinder was a bit higher when fully seated, maybe that could be an issue, I have added half turn more on that one and will test it today.


Also next to a Pilot jet screw, there is something blanked off next to it. What's that?
One one of the videos someone said to remove the blanks when cleaning.

[unfazed]

It's a blank, used in other applications, but not the fazer.You may have a leaking float valve allowing to much fuel at tickover, O ring ma have hardened and become brittle. allowing fuel to bypass the needle jet.
This is a common issue on the fazers as they are now 20 plus years old.

[siedlik]

I have put the carbs back and they run pretty good, but after warm up they run a bit crap at idle.
Tested the exhaust temps, and the exhaust 1st - 200C, 2nd - 200C, 3rd - 120C, 4th - 150C


Could the coils go bad after warmup or something like that ?
The bike runs fine at normal speed, but crap at idle.


Tested the coils at cold, and they are in spec. Do the specs change when they are warmed up ?


Would it be possible that just the right side of the coils goes bad after warmup?
Will do more tests tomorrow and order new coils set.

[BBROWN1664]

the same coil does 1&4 and the same coil does 2&3 so a bad coil would affect its other cylinder too.

Have you tried balancing the carbs?

[siedlik]

I did balance the carbs.


At the start the engine runs good, not perfect. 
Exahoust temps were 200, 200, 190, 160.
But after a warmup idle goes bad and the temps go to 230, 230, 150, 100.     
The carbs cant go bad after a warmup, it has to be an electrical issue.  I will replace the coils, hopefully, that will fix it.
After a warmup, I think the resistance of the coils is going up and most of the sparks are going into the short leads with is cylinders 1 and 2.

[siedlik]

the same coil does 1&4 and the same coil does 2&3 so a bad coil would affect its other cylinder too.

Have you tried balancing the carbs?

New coils fixed the issue, all temps are 230 now.