Quote Originally Posted by dom14 View Post
RB30 carby can be pretty weather sensitive when it's on dual fuel.
I had been having misfiring and occasional backfiring.
I basically put in a second dizzy which I opened up and cleaned before I put it in.
No backfiring or misfiring now, but it idles pretty low when cold(about 400ish) on LPG.
Petrol idling is slightly higher(about 650ish).
I think the problem is in the carby idle circuit.
I haven't bothered to tune the carby yet, 'cos the problem isn't urgent.
Open up the dizzy and give it a good clean and lube the mechanical parts.
I would also try advancing the timing a little bit as well.
RB30 Patrol dizzy is electronic, but there're vacuum advance & mechanical(centrifugal I think) advance, which are both mechanical. They need lubing and service after a long time use.

In mine, ignition lead no-2 was showing 5200 ohm resistance, which was fair bit higher than the rest(twice as much).
But, I still haven't replaced the leads.

As for the OPs issue, I think it's the carby, according to my similar experiences.
Having said that, it's worth checking the fuel filter, gauz filter and fuel pressure, before opening up the carby and trying to tune it.
Mine isn't dual fuel so at least I don't have the complication of LPG to deal with, it is weird as it is intermittent, but I'm going to have a look at the rest of the items on the list on the previous page, and that will include replacing the fuel filter and having a look at the dizzy, so I'll see if that shows anything.

I've found a an old school carby bloke that will rebuild the carby for $380, I'm considering it just to eliminate that as the cause, but I might do all the other things first as I'd rather not spend the best part of $400 if I don't have to just for a carby freshen up, but if the other things don't show up any problems, I reckon I'll be doing the carb, having to constantly maintain revs on rock and clay descents and climbs can be a brown pants experience. (Yes a sensible person might ask why I would even go on the hill in the first place when it wouldn't idle, but it was working fine when we started the track)...