Carb Tuning Advice

[boostaholic]

Hello Everyone!

I am in need of some carb tuning help.
The bike - 1980 cb750k.
Mods - carpy 4-1, stock airbox.
A side note - Bike has new carb boots on it, old clamps. Tested it for vacuum leaks while running by spraying starting fluid on boots. Didn't spike in RPMs, didn't spray carbs themselves though.

So, the problem- Upon initial fire-up, the bike ran ok. Cylinder 4 didn't seem to be firing, but let it warm up anyways. After about a minute with choke on, idle dropped and smoothed out a bit, cylinder 4 decided to start working with some carb adjustment. Pushed choke in and bike died. So re-started with choke about half way out, ran great. Revs nicely but pops when losing RPMs. So initial thoughts are that its obviously running lean if the choke needs to be "on" to allow proper running conditions. Furthermore, I have the adjustment screws turned out basically all the way (4 turns).
I'm a newbie when it comes to carburetors, I would appreciate some advising in terms of jet sizing and maybe overall tech help. What jets do what.. etc... etc..

Thank you!

[TOOLS1]

I am guessing that you just got the bike, and it has been sitting for years without being run, and you just got it fired up. It sounds like your pilot jets (slow jets, idle to 1/4 throttle) are plugged. There is a thread on here in the "Repair Tips and Tricks" section that details a rebuild on the CV carbs that you have. Also you can download the factory service manual for free from the manuals thread at the top of the home page.
TOOLS