Thankyou Wjajr for your continued advice I'll try swap these back in tomorrow. Originally I believe the carb came fitted with 61 or 62 jets and a 6.5 pv. The supplier said they adjust these parts for the application.

I haven't done the valves no, I will look into doing that tomorrow hopefully (It's just after midnight down under).

I will try get some more accurate readings with the vac gauge at specific RPMS and throttle positions and report back.

Just to update I've checked the leads, the plugs, the manifold, pulled apart and cleaned the carb (blue carb cleaning through all holes, checked with a light that none were blocked, ensured all ports are being used correctly etc etc), tried with the air filter on or off, put in 10L of fuel.

Hi Brussel, you just bought one of the most important additions to your toolbox, and it's value is enormous in comparison to it's low price!

This link may give you some input on how to interpret your possible vacuum gauge readings: (when you click the green buttons, beware that some of them have a two-stage response)

How to Use and Interpret a Vacuum Gauge

There are also several other similar applications on the web.

Olaf

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Aspenized

Thanks Olafla!