TONYT25T25 wrote:Tks, choke does cut out when engine warmed up so must be ok there.
Not necessarily. The choke does two things:
1) it operates a flap to close off most of the airflow, so as to enrich the fuel air mixture when the engine is cold. As the choke comes off the flap opens.
2) it operates a stepped cam for the fast idle screw to ride on. As the choke comes off, the fast idle screw moves down onto successively lower steps of this cam, until eventually the fast idle screw comes off the cam altogether, at which point the idle speed is controlled by the main idle speed screw.
To engage the fast idle in the first place, you have to depress the accelerator before starting the engine, as pointed out by Aidan.
This puts the fast idle screw on the top step of the cam (or the highest one necessary when it's not so cold out). *Then* you start the engine without touching the accelerator. If you're doing that but you're not getting any sort of fast idle, then it's possible that the fast idle screw isn't adjusted properly, so it isn't increasing your engine speed when cold.
There are instructions for adjusting this screw. If there's a tamper-proof cap on it, it probably doesn't need adjustment, but that's no guarantee. Because this screw is so difficult to get to it should not be adjusted while the engine is running (you have to lean right over the engine), so it's a matter of trial and error. And because cold engine speed will vary depending on the amount of choke, the adjustment is specified with a warm engine, i.e. choke fully open.
So warm up the engine and turn it off, then, with the airbox and hose removed, set the fast idle screw (manually) onto the *first step down* (as shown in the photo - not the top step). Make sure the choke flap is fully open (vertical), then start the engine. Engine RPM should be ~2300. If it's not, turn off the engine, adjust the screw in or out to raise or lower that speed, then start the engine again and check it.