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If it won't idle under 2k and needs the throttle screw way in, then the pilot circuit is partially blocked too most likely. Messing around with the mixture screw won't help. I'd just whip the carb off and give it some love.
Jung-
Earlier in the year it was idling at 1200-1500 as it should, but I couldn’t trust it not to drop below 1k and stall when stopping at lights and junctions. Then after a month or so of fiddling it seemed to be happier at 2k.
When I last cleaned out the carb and replaced some parts a couple months ago, the idle screw was set to.... 3 1/2 turns? It was set to spec, then I set the throttle screw to keep it open and idle at 2k for above reasons.
Bear in mind that back in November the carb was ‘cleaned’ by a well-recommended mechanics, and since then was only the £££ Shell fuel, plus Redex for months. Then by March I’d stripped and used carb cleaner fluid twice myself to try get past the stalling-on-idle issue and stopped with the Redex.
Suppose it’ll be a full strip down of the carb yet again then. Woohoo.
pdlouche
@Airhead hmmmm. Thanks will consider that. Spark plug core has been the lighter shade of brown but looked as close to ideal as possible. Possible float height, hadn’t thought of that.
I’d put the main jet needle clip back to the centre as I think it was set one step closer to lean before, but that didn’t change anything - besides it’s an issue before that jet comes into the equation. When set two steps richer it was sputtery and shit. Maybe it has a leak somewhere.
It may indeed help adjusting the timing screw vs idle screw. Some months ago I had to leave the idle at a steady 2k because lower than that it used to hunt and until recently I couldn’t trust it not to stall anyway. Will look for my little idle screwdriver, see if I can adjust it and get it running lower consistent idle without immediately stalling on throttle.
@jackbepablo I’ll check the fuel cap but the noise of air/vapour escaping in the heat leads me to believe there’s no vacuum there. I have an inline fuel filter that seems to show nice steady fuel flow. Will check for kinks elsewhere.
@Jung this is probably the next step. No amount of high quality Shell fuel through an extra inline filter can save me from a clogged jet.