Suzuki 2 Strokes

I've had the T500 on the road for about 1000 miles now and have been unable to get rid of a slight pinging in the engine. It seems to occur around 80-100kph on a steady throttle. Things I have done so far include
complete refurb of carbs and checked all jets as standard.
Float levels checked ok.
Swapped from standard points to electronic ignition
moved ignition timing from standard to slightly retarded.
Tested with different fuels from 92-98 octane and added octane booster with no change.
If I tap the choke on slightly while riding the problem goes away which suggests it's a fuel related issue.
My next step would be to raise the jet needles one notch and if that doesn't work then maybe go for a larger pilot jet.
Has anyone experienced the same problem and worked out a fix for it.

I would recommend trying needle jets one size larger. That will increase fueling proportionately more at lower throttle openings.

I saw in a tuning post to put some masking tape on the throttle grip with markings on it to show idle and half throttle and then another small piece of tape on the switch assembly , that way when you hear the sound you can glance at the grip to see just where you are on the throttle . This should help you narrow down what carb area needs to be looked into .