Thunderbird 900 surging

It wont be the main jet that is above half throttle, probably the pilot jets ,not sure but maybe the needles are worn too.Have you tried a couple of tanks of fuel with redex in to clean the jets through,it has helped me in my bike with the low down smooth running. The t300 bikes are known to be a bit iffy and lumpy below 3000 rpm but not surging.
Is it well serviced with new air filter etc?

 

Hi, I think you have put enough redex in but think you need to do more than just one tank. I have found it made my bike better but use it every fill up now,it takes time to do its magic. Again just because the air filter is not up for a change as far as mileage goes, depending how the bike was stored there could be loads of dust making the mixture rich. When my bike was serviced, the filter had almost a nest of small twigs and fluff in it, new filter made a difference immediately.

Also you may well find that the low mileage is the cause of the problem,old fuel will have gummed the jets up. I would think to be honest that the carbs will probably need ultrasonic cleaning and maybe new jets too.

 

Great news mate. I should have thought about that when you said the mileage, they need checking every 12000.