Dirty Air Filter = black plugs?

KZ650. Only 1 and 3 are fouling. Carbs were built 2 years ago and then stored with the bike in a climate controlled garage - my uncles.
Can a dirty air filter cause plug fouling? According to my uncles maintenance log, the filter hasnt been cleaned since 2022!!!

Worth checking but unlikely given that it appears the bike hasn't been used much in that time

A dirty air filter will restrict airflow and cause a rich mixture BUT as your using the original airbox it would affect all four cylinders not just two.
As Guy said a 2or 3 year old airfilter that's only got a few miles on it is not your problem unless you've got a bird/rodent nest in it. It's not unheard off! 
My money is on hard choke plunger seals not sealing. 

Ditto on the choke plunger seals.

Warren3200gt wrote:

A dirty air filter will restrict airflow and cause a rich mixture BUT as your using the original airbox it would affect all four cylinders not just two.
As Guy said a 2or 3 year old airfilter that's only got a few miles on it is not your problem unless you've got a bird/rodent nest in it. It's not unheard off! 
My money is on hard choke plunger seals not sealing. 

 

Thanks so much Warren!

Can I ask a dumb question? So how do i fix this? Take the carbs off ( i hear its a nightmare with the airbox) and then what? Where do I get the seals?

Update: After I posted the above, I did some research. I see its these things from Z1. Guess I have to take the carbs off to put them on?

Note that the carbs were rebuilt not too long ago. Could it be something else?  



 

Those look like the "outer dust seals" the actual plunger seals are not straightforward to replace but member Zed1015 offers a referb service on these  (many members have used and praise the service offered) You could reach out to him through the PM function

AlexRocco wrote:

 

Can I ask a dumb question? So how do i fix this? Take the carbs off ( i hear its a nightmare with the airbox) and then what? Where do I get the seals?

Update: After I posted the above, I did some research. I see its these things from Z1. Guess I have to take the carbs off to put them on?

Note that the carbs were rebuilt not too long ago. Could it be something else?  







 

Alex.
It's the seals in the end of the plunger that closes off the fuel supply when the choke is off that causes rich running issues.
Once they start leaking you are effectively running on anything from partial to full choke depending on the severity.
You can't buy the seals because the the plungers were never supposed to be a servicable part but i developed a way of replacing them with fuel resistant Viton without damaging the original swaged retaining edge.
You would need to remove the plungers and send them to me for repair.
Email me at zed.1015@yahoo.co.uk for more info.
The pic below is before on the left and after with new seal on the right.
Rob.

Take Serious the note of Zed1015's recommendations!! You'll chase your tail jetting/running issues if those choke plungers don't seal correctly. I go about it differently then ZED does but the outcome is the same, sealing. I'd reference what i do but don't want to step on toes or piss on a proven/fantastic service Zed provides. But note, those plungers are just a valve to seal off needed or un-needed fuel at start and running scenarios, nothing complicated but totally needed to function correctly.