Your idle jet will be a screw in style jet. Should look like this one.

https://www.partzilla.com/product/ho...xoC2QoQAvD_BwE

 

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​​​​​​Update:
​​​​​​Have a spark
have compression of around 140 at idle
gone through the jets again definitely not blocked and cleaned whilst out float sitting fine fuel supply working fine all air tight and the cylinder still running cold about 100-150° lower than other 3 and a slight misfire after blipping the throttle. Do you have any ideas where to look next looking at maybe cam chain tensioner diaphragms or needle not pulling up and not getting enough fuel in to the 4th cylinder.
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Cam chain tensioner wouldn't be the cause of the symptom you describe. 140 psi sounds adequate, but you also want to check it against the other 3 cylinders. They should all be around the same. If you have 1 cylinder measuring significantly lower, then I would say you have a compression problem but I still doubt this is your problem. If you have spark at cylinder 4, this definitely sounds like a fueling issue. You may want to check to make sure the carburetors are synchronized. This can cause running issues, but I would still lean towards a clogged jet/passage somewhere.

 

There's more to cleaning carbs than just jets. It's like garden hose and everyone's focused on sprayer at end (jets). But what about the 20 golf-***** stuck in hose along way??? To properly restore carbs to OEM fresh clean condition, needs:

- scrubbing out all secret hidden passages in carb-body with brushes and PEA-based fuel-system cleaner
- poking out all bleed holes with soft copper wire of matching gauge
- ultrasonic soak everything
- micro soda-blast
- replace all rubbers, float-valves, fuel-rail O-rings, pilot-screw O-rings, float-bowl seals
- set and test float-levels
- sync carbs with manometers

Skipping any of these steps will result in bike running unevenly.


Scrub-brushes from amazon:
Ultrasonic cleaner:
Micro soda-blaster: https://vaporhoningtechnologies.com/...-a-carburetor/

Manometers:

 

well look at that! I was totally mistaken - good catch!

https://www.hondasportpartswarehouse...-harness-99-00