Hi Lewis
Your description certainly would make fuel flow a first candidate for elimination.
I suggest you get a cheap plastic or glass graduated kitchen jug.
(My good lady gets offended if I use her kitchenware for oil and petrol!)
Either fix up a big tube or put a drip tray underneath
No not one of the kitchenfuhers roasting trays! but like one
Take off the carb body bottom nut.
Turn on petrol tap for one minute
Catch and measure what has flowed
I would guess that you should have about 600ml / min for your bike.
If you have a rusty tank and you have installed a tap with filter, these are very prone to clog up quickly, so sorry, but check this again to be sure.
If all is ok, then check in the float chamber to see that the groove in the needle that locates the float is in good condition and the spring clip is secure. Sometimes after long service, the parts become worn and the float gets out of position and so effects the fuel height.
Check out the hole the needle seat in to be sure that their is no debris that impeds fuel flow here.
Kind Regards
Roger M
