TB42 Starts fine on gas, rough on petrol

Hey all, I've got a 1990 GQ Patrol, TB42 carby fed with petrol and gas. Just wondering if anyone would know why my engine starts and idles fine from cold when I have it on gas, and when I switch it to petrol once warm it runs fine, but if I start it from cold on petrol it won't fire properly and struggles to idle, any help appreciated!

Gas dries out the seals in the carby and can block the idle jet as well.

Is there any quick way to repair this?

I think you will find that it is tuned more for Gas than Petrol and will run better on Gas