Are you talking about the mixture control valve located under the small plastic cover before/under the tank (where the ignition coils do also sit)? I dont believe that its responsible for a weak engine, but You can remove it and throw it away as far as possible, then close the according pipes at the intake rubber.

poor engine power is often caused by wrong camshaft timings or a weak rubber duct on the air cleaner box.

Quick commonly it's one of the gazillian vacuum tubes that go to/come from the mix valve. Don't forget to plug the opening on the manifold and check the vacuum hoses to the petcocks.

Cheers,
Greg

I'm in the same boat ! .... Love to hear some suggestions 😢

thanks for the help guys ,just to let you know that after messing with the carbs she still wouldn't run correctly ,rear cylinder hot front lukewarm only .So checked compression both cylinders showed up ok 150/160 which was strange as I had better compression on the duff pot,so I did a quick leak down test and discovered that the inlet valve on the front pot was so tight their was no gap.Adjusted the tappet and so far all seems good which begs the question how tight are the rear pots tappets but thats for another day as it looks like a bit of a task just to get to them ,maybe because they're so hard to get at leads to total neglect which after the chat I had with the previous owner with his records of services and repairs is at odds with my expectations

ok one last quick one and hope I am sorted ,the question today is , can a faulty tci produce a perfectly good spark on one cylinder but a weak spark on the other ,so one pot runs hot as it should but the other is only warm to touch ,i have checked the ohms on the pick ups and both read as stated in the manual